Patent Publication Number: US-2022227833-A1

Title: Cd80 variant proteins and uses thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Application No. 62/839,542, filed on Apr. 26, 2019, the content of which is hereby incorporated by reference in its entirety for all purposes. 
     DESCRIPTION OF THE TEXT FILE SUBMITTED ELECTRONICALLY 
     The contents of the text file submitted electronically herewith are incorporated herein by reference in their entirety: A computer readable format copy of the Sequence Listing (filename: Sequence_Listing_2_SeqList_ST25.txt, date recorded: Dec. 7, 2021, file size ˜46 kilobytes). 
    
    
     BACKGROUND 
     T-cell lymphocytes play a critical role in cell-mediated immunity by providing for an adaptive response to specific pathogens. T-cell activation depends on activation of at least two signaling pathways, one that is antigen specific and the other that is antigen nonspecific. Antigen-specific activation of T-cells is mediated by peptide/major histocompatibility complexes on antigen-presenting cells interacting with specific T-cell antigen receptors. Binding of B7-related molecules expressed on antigen-presenting cells, which are CD80 (B7-1) and CD86 (B7-2), to CD28 and/or CTLA-4 on T-cells provides important antigen-nonspecific costimulatory signals essential for optimum immune responses. The binding of CD80 to the T-cell homodimers of CD28 and CTLA-4 generates costimulatory and inhibitory signals in T-cell, and the binding of CD80 to PD-L1 interrupts the interaction between PD-1 and PD-L1 removing the inhibitory signals of T-cell activation. Because these signaling pathways determine the magnitude of a T-cell response to antigen, as well as downstream responses to antigen, agents that specifically modulate one or more costimulatory signals, e.g., by modulating one or more of the interactions between CD80 and CD28 and/or CTLA4, may be effective in treating disorders that result from dysregulated cell-mediated immune responses. 
     CD80 is a member of the immunoglobulin super-family (IgSF) with its extracellular domain consisting of one amino-terminal Ig variable-like (IgV) and one membrane proximal Ig constant-like (IgC) domain. Efforts modulating the binding affinities towards these three target proteins of CD80, CTLA-4, PD-L 1  and CD28 have been carried out. (Peach et al., (1995) JBC, 270 (36), 21181-21187). 
     CD28 favors the binding of monomeric ligands and CTLA-4 favors that of dimeric ligands, the ratio of CD80 in monomeric versus multimeric forms could influence the ensuing immune response. Accordingly there is a need to provide improved CD80 variants with increased, decreased or a combination of increased and decreased affinity to each of the CTLA-4, PD-L1 and CD28 ligands to selectively modulate T-cell activation to achieve specific therapeutic effects. The present disclosure provides methods and compositions relating to the same. 
     SUMMARY 
     The present disclosure provides variant CD80 polypeptides. In some embodiments, the variant CD80 polypeptides comprise an amino acid sequence having at least 80% amino acid sequence identity to SEQ ID NO: 1, wherein the variant CD80 polypeptide comprises one or more of the amino acid substitution modifications compared to SEQ ID NO: 1, wherein the one or more substitution modifications are at positions  131 ,  139 ,  155 ,  165 , or  166  of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises two or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the two or more substitution modifications are at positions  130 ,  131 ,  139 ,  155 ,  156 ,  165 , or  166  of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises three or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the three or more substitution modifications are at positions  130 ,  131 ,  139 ,  155 ,  156 ,  165 , or  166  of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises four or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the four or more substitution modifications are at positions  130 ,  131 ,  139 ,  155 ,  156 ,  165 , or  166  of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises five or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the five or more substitution modifications are at positions  130 ,  131 ,  139 ,  155 ,  156 ,  165 , or  166  of SEQ ID NO: 1. 
     In some embodiments, the variant CD80 polypeptide has increased or decreased binding affinity for CTLA-4, CD28, or PD-L1 compared to SEQ ID NO: 1. 
     In other embodiments, the variant CD80 polypeptide further comprises a second polypeptide that is capable of dimerizing. In some embodiments, the second polypeptide is an immunoglobulin Fc domain, which is a human IgG1 Fc domain, a human IgG2 Fc domain, a human IgG3 Fc domain, a human IgG4 Fc domain, a mouse IgG1 Fc domain, a mouse IgG2a Fc domain, a mouse IgG2b Fc domain, or a mouse IgG3 Fc domain. In some embodiments, the variant CD80 polypeptide further comprises a therapeutically active moiety. 
     The present disclosure also provides a polynucleotide encoding the variant CD80 polypeptide of the present disclosure, which is a synthetic nucleic acid or cDNA. In some embodiments, the polynucleotide is operably linked to a transcriptional control element that is functional in a eukaryotic cell. 
     The present disclosure also provides a vector comprising the polynucleotide of the present disclosure, which is an expression vector, a mammalian vector or a viral vector. 
     The present disclosure also provides a cell comprising the vector of the present disclosure, which is a mammalian cell including a human cell. 
     The present disclosure further provides a pharmaceutical composition comprises the variant CD80 polypeptide of the present disclosure, further comprising a pharmaceutically acceptable excipient. In some embodiments, the pharmaceutical composition is sterile. In some embodiments, a kit comprises the pharmaceutical composition of the present disclosure, and instructions for use. 
     The present disclosure also provides an article of manufacture comprises the pharmaceutical composition of the present disclosure in a vial, which is sealed. In some embodiments, a kit comprises the article of manufacture of the present disclosure, and instructions for use. 
     The present disclosure further provides a method of modulating an immune response in a subject, comprising administering the pharmaceutical composition of the present disclosure to the subject. In some embodiments, modulating the immune response treats a disease or condition in the subject. In some embodiments, the immune response is increased or decreased. In some embodiments, the disease or condition is a tumor or cancer. In some embodiments, the disease or condition is an inflammatory or autoimmune disease or condition. 
     The present disclosure further provides a method of treating a disease or condition in a subject, comprising administering the pharmaceutical composition of the present disclosure to the subject. In some embodiments, the disease or condition is an infection. In some embodiments, the disease or condition is a tumor or cancer. In some embodiments, the disease or condition is an inflammatory or autoimmune disease or condition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  provides an amino acid sequence of a Wild-type Human CD80 Extracellular Domain (ECD) (SEQ ID NO: 1), which is obtained from UniProtKB P33681 (CD80 HUMAN). Amino acids are bolded and underlined to display positions of substitutions/mutations of interest. 
         FIG. 2  provides an amino acid sequence of a Human IgG1 Fc Domain (SEQ ID NO: 2), which is partially obtained from UniProtKB P01857 (IGHG1 HUMAN), Immunoglobulin heavy constant gamma 1. 
         FIG. 3  provides an amino acid sequence of a Human IgG2 Fc Domain (SEQ ID NO: 3), which is partially obtained from UniProtKB P01859 (IGHG2 HUMAN), Immunoglobulin heavy constant gamma 2. 
         FIG. 4  provides an amino acid sequence of a Human IgG3 Fc Domain (SEQ ID NO: 4), which is partially obtained from UniProtKB P01860 (IGHG3 HUMAN), Immunoglobulin heavy constant gamma 3. 
         FIG. 5  provides an amino acid sequence of a Human IgG4 Fc Domain (SEQ ID NO: 5), which is partially obtained from UniProtKB P01861 (IGHG4 HUMAN), Immunoglobulin heavy constant gamma 4. 
         FIG. 6  provides an amino acid sequence of a Mouse IgG1 Fc Domain (SEQ ID NO: 6), which is partially obtained from UniProtKB P01868 (IGHG1 MOUSE), Ig gamma-1 chain C region secreted from. 
         FIG. 7  provides an amino acid sequence of a Mouse IgG2a Fc Domain (SEQ ID NO: 7), which is partially obtained from UniProtKB P01863 (GCAA MOUSE), Ig gamma-2A chain C region, A allele. 
         FIG. 8  provides an amino acid sequence of a Mouse IgG2b Fc Domain (SEQ ID NO: 8), which is partially obtained from UniProtKB P01867 (IGG2B MOUSE), Ig gamma-2B chain C region. 
         FIG. 9  provides an amino acid sequence of a Mouse IgG3 Fc Domain (SEQ ID NO: 9), which is partially obtained from UniProtKB P03987 (IGHG3 MOUSE), Ig gamma-3 chain C region. 
         FIG. 10  provides an amino acid sequence of a Human CD28 (SEQ ID NO: 10), which is obtained from UniProtKB P10747 (CD28 HUMAN), T-cell-specific surface glycoprotein CD28. 
         FIG. 11  provides an amino acid sequence of a Human CTLA-4 (SEQ ID NO: 11), which is obtained from UniProtKB P16410 (CTLA4 HUMAN), Cytotoxic T-lymphocyte protein 4. 
         FIG. 12  provides an amino acid sequence of a Human PD-L1 (SEQ ID NO: 12), which is obtained from UniProtKB Q9NZQ7 (PD1L1 HUMAN), Programmed cell death 1 ligand 1. 
         FIG. 13A  depicts a schematic diagram of a CD80-Fc Expression cassette, encoding (i) Leader Sequence ( FIG. 13B ), (ii) CD80 (either wild-type human CD80 or Mutated human CD80 variant of interest taught in the present disclosure) and (iii) Ig Fc domains of interest taught in the present disclosure, from an expression vector.  FIG. 13B  provides an amino acid sequence of leader sequence (SEQ ID NO: 13) obtained from a Human IgG heavy chain (GenBank: QBK47409.1).  FIG. 13C  depicts a schematic diagram of a CD80-Fc fusion protein consisting of two CD80-Fc fusion polypeptides dimerized and connected via disulfide bonds. 
         FIG. 14A  provides an amino acid sequence of a Human CD80-Fc fusion polypeptide (SEQ ID NO: 14) expressed from a hCD80-Fc expression construct.  FIG. 14B  provides an amino acid sequence of a wild type mouse CD80 sequence (SEQ ID NO: 15). 
         FIG. 15A  depicts SDS-PAGE analysis results of selected and purified CD80-Fc Fusion Proteins in a non-reducing condition.  FIG. 15B  depicts SDS-PAGE analysis results of selected and purified CD80-Fc fusion polypeptides in a reducing condition. Samples loaded with purified CD80-Fc Fusion Protein in  FIGS. 15A-15B  are as follows; Lane 1: Molecular Weight Marker; Lane 2: S131F, 1.5 ug/lane; Lane 3: S131R, 1.5 ug/lane; Lane 4: S131E, 2.0 ug/lane; Lane 5: S131D, 1.6 ug/lane; Lane 6: S131Q, 1.6 ug/lane; Lane 7: A165V, 1.2 ug/lane; Lane 8: A165I, 1.6 ug/lane; Lane 9: A165F, 1.6 ug/lane; Lane 10: A165R, 1.6 ug/lane; Lane 11: A165D, 1.6 ug/lane; Lane 12: A165Q, 1.6 ug/lane. 
         FIG. 15C  depicts SDS-PAGE analysis results of selected and purified CD80-Fc Fusion Proteins in a non-reducing condition.  FIG. 15D  depicts SDS-PAGE analysis results of selected and purified CD80-Fc fusion polypeptides in a reducing condition. Samples loaded with purified CD80-Fc fusion protein in  FIGS. 15C-15D  are as follows; Lane 1: Molecular Weight Marker; Lane 2: V166A, 10 ug/lane; Lane 3: V166T, 10 ug/lane; Lane 4: V166L/L139V, 10 ug/lane; Lane 5: S156A/V155A, 10 ug/lane; Lane 6: S156A/V1551, 10 ug/lane; Lane 7: S156A/V155T, 10 ug/lane; Lane 8: S156A/T130A, 10 ug/lane; Lane 9: S156A/V166A, 10 ug/lane; Lane 10: S156A/V166L/L139V, 10 ug/lane. 
         FIG. 15E  depicts SDS-PAGE analysis results of selected and purified CD80-Fc Fusion Proteins in a non-reducing condition.  FIG. 15F  depicts SDS-PAGE analysis results of selected and purified CD80-Fc fusion polypeptides in a reducing condition. Samples loaded with purified CD80-Fc fusion protein in  FIGS. 15E-15F  are as follows; Lane 1: Molecular Weight Marker; Lane 2: S131V, 10 ug/lane; Lane 3: V155A, 10 ug/lane; Lane 4: V155I, 10 ug/lane; Lane 5: V155T, 10 ug/lane. 
         FIG. 16A  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A —double substitutions/mutations), and three positions (S156I/A165S/S131A—triple substitutions/mutations). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 16B  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S156 (S156F, S156R, S156E, S156D, and S156Q). CD80-WT protein is used as a positive control. 
         FIG. 16C  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131V, S131I, S131F, S131R, and S131E). CD80-WT protein is used as a positive control. 
         FIG. 16D  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 or A165 (S131D, S131Q, A165V, A165I, and A165F). CD80-WT protein is used as a positive control. 
         FIG. 16E  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position A165 (A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 16F  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation (T130A, S131V, L139V, V155A, V155I, V155T, S156A, V166A, V166L, V166T, V155A/S156A, V155I/S156A, and V155T/S156A). CD80-WT protein is used as a positive control. 
         FIG. 17A  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CD28. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), and three positions (S156I/A165S/S131A—triple substitutions/mutations). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 17B  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CD28. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S156 (S156F, S156R, S156E, S156D, and S156Q). CD80-WT protein is used as a positive control. 
         FIG. 17C  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CD28. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131V, S131I, S131F, S131R, and S131E). CD80-WT protein is used as a positive control. 
         FIG. 17D  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CD28. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 or A165 (S131D, S131Q, A165V, A165I, and A165F). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 17E  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner CD28. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position A165 (A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control. 
         FIG. 18A  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner PD-L1. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), and three positions (S156I/A165S/S131A—triple substitutions/mutations). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 18B  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner PD-L1. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S156 (S156F, S156R, S156E, S156D, and S156Q). CD80-WT protein is used as a positive control. 
         FIG. 18C  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner PD-L1. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131V, S131I, S131F, S131R, and S131E). CD80-WT protein is used as a positive control. 
         FIG. 18D  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner PD-L1. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 or A165 (S131D, S131Q, A165V, A165I, and A165F). CD80-WT protein is used as a positive control. 
         FIG. 18E  depicts results of binding assays by ELISA to test binding affinity of variant CD80-Fc Fusion Proteins to immobilized binding partner PD-L1. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position A165 (A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 19  depicts results of binding assays of each variant CD80-Fc Fusion protein including single, double and triple mutations, to a binding partner human CTLA-4, using BlAcore model X100. 
         FIG. 20A  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), three positions (S156I/A165S/S131A—triple substitutions/mutations) and one position at S156 (S156F, S156R, and S156E). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 20B  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing CTLA-4. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position at S156, S131, or A165 (S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 21A  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing CD28. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), three positions (S156I/A165S/S131A—triple substitutions/mutations) and one position at S156 (S156F, S156R, and S156E). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 21B  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing CD28. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position at S156, S131, or A165 (S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 22A  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing PD-L1. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), three positions (S156I/A165S/S131A—triple substitutions/mutations) and one position at S156 (S156F, S156R, and S156E). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 22B  depicts results of cell surface binding assays by FACS to test binding affinity of variant CD80-Fc Fusion Proteins to Flp-in 293 cells expressing PD-L1. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position at S156, S131, or A165 (S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 23A  depicts results of functional assays for IL-2 release to test ability of variant CD80-Fc Fusion Proteins for T-cell activation. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), and three positions (S156I/A165S/S131A -triple substitutions/mutations). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 23B  depicts results of functional assays for IL-2 release to test ability of variant CD80-Fc Fusion Proteins for T-cell activation. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131V, S131I, S131F, S131R, S131E, S131D, and S131Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 23C  depicts results of functional assays for IL-2 release to test ability of variant CD80-Fc Fusion Proteins for T-cell activation. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S156 (S156F, S156R, S156E, S156D, and S156Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 23D  depicts results of functional assays for IL-2 release to test ability of variant CD80-Fc Fusion Proteins for T-cell activation. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position A165 (A165V, A165I, A165F, A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 24  illustrates crystal structure of CD80 dimer (composed of IgC domain, interdomain hinge, and IgV domain) complexed with CTLA-4. Mutation positions in IgC domain are presented as follows: T130, S131, L139, V155, S156, A165, and V166. 
         FIG. 25A  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165 S/S 131A—double substitutions/mutations), CD80-WT protein is used as a positive control. 
         FIG. 25B  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at three positions (S156I/A165S/S131A—triple substitutions/mutations) and one position at S156 (S156F, S156R, and S156E). CD80-WT protein is used as a positive control. 
         FIG. 25C  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S156 or S131 (S156D, S156Q, S131V, and S1310. CD80-WT protein is used as a positive control. 
         FIG. 25D  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131F, and S131R). CD80-WT protein is used as a positive control. 
         FIG. 25E  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131E, and S131D). CD80-WT protein is used as a positive control. 
         FIG. 25F  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 or A165 (S131Q, A165V, A1651, and A165F). CD80-WT protein is used as a positive control. 
         FIG. 25G  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position A165 (A165R, A165E, A165D, and A165Q). CD80-WT protein is used as a positive control. 
         FIG. 25H  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position V155 (V155A, V1551, and V155T). CD80-WT protein is used as a positive control. 
         FIG. 25I  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at one position V166 (V166A, and V166T), and two positions (V166L/L139V, and S156AN155A—double substitutions/mutations), CD80-WT protein is used as a positive control. 
         FIG. 25J  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156A/V1551, S156A/V155T, S156A/T130A, and S156A/V166A—double substitutions/mutations), CD80-WT protein is used as a positive control. 
         FIG. 25K  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at three positions (S156A/V166L/L139V—triple substitutions/mutations), and one position S156 or A165 (S1561, S156A, and A165S). CD80-WT protein is used as a positive control. 
         FIG. 25L  depicts results of CTLA-4 blockade assay to evaluate the ability of variant CD80-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Types of variant CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 or S156 (S131A, S156V, S156L, and S156I). CD80-WT protein is used as a positive control and human IgG1 protein is a negative control. 
         FIG. 26A  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (S156I/A165S, S156I/S131A, and A165S/S131A—double substitutions/mutations), at three positions (S1561/A165S/S131A—triple substitutions/mutations), and at one position S156 (S156F). CD80-WT protein is used as a positive control. 
         FIG. 26B  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitution/mutation at a single position S156 (S156R, S156E, S156D, and S156Q). Human IgG1 protein is used as a negative control. 
         FIG. 26C  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitution/mutation at a single position S131 (S131V, S1311, S131F, S131R, S131E, and S131D). 
         FIG. 26D  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitution/mutation at a single position S131 or A165 (S131Q, A165V, A1651, A165F, A165R, A165E, A165D and Al 65Q). 
         FIG. 26E  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitution/mutation at a single position S156, A165 or S131 (S156A, A165S, S131A, and S156V). 
         FIG. 26F  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitution/mutation at a single position V155 or V166 (V155A, V155I, V155T, V166A, and V166T). 
         FIG. 26G  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at two positions (V166L/L139V, S156A/V155A, S156A/V1551, S156A/V155T, S156A/T13OA, and S156A/V166A—double substitutions/mutations). 
         FIG. 26H  depicts results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Types of variant CD80 polypeptides tested herein are as follows: amino acid substitutions/mutations at three positions (S156A/V166L/L139V—triple substitutions/mutations), and at one position S156 or A165 (51561, and A165S). 
         FIG. 27  depicts results of in vivo efficacy of variant CD80 Proteins in CT26 Syngeneic Mouse Model. 
         FIG. 28  depicts results of in vivo efficacy of variant CD80 Proteins in MC-38 Syngeneic Mouse Model. 
         FIG. 29A  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CD28. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 (T165E, T165Q, T165R, T165A, and T165S). Mouse CD80-WT protein is used as a positive control. 
         FIG. 29B  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CD28. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 or S131 (T165V, T1651, T165F, T165D, and S131V). Mouse CD80-WT protein is used as a positive control. 
         FIG. 29C  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CD28. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131I, S131F, S131R, S131E, and S131Q). Mouse CD8O-WT protein is used as a positive control. 
         FIG. 29D  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CD28. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131A, and S131P). Mouse CD80-WT protein is used as a positive control. 
         FIG. 30A  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse PD-L1. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 (T165E, T165Q, T165R, T165A, and T165S). Mouse CD80-WT protein is used as a positive control. 
         FIG. 30B  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse PD-L1. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 or S131 (T165V, T165I, T165F, T165D, and S131V). Mouse CD80-WT protein is used as a positive control. 
         FIG. 30C  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse PD-L1. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131I, S131F, S131R, S131E, and S131Q). Mouse CD80-WT protein is used as a positive control. 
         FIG. 30D  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse PD-L1. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131A, and S131P). Mouse CD80-WT protein is used as a positive control. 
         FIG. 31A  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CTLA4. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 (T165E, T165Q, T165R, T165A, and T165S). Mouse CD80-WT protein is used as a positive control. 
         FIG. 31B  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CTLA4. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position T165 or S131 (T165V, T165I, T165F, T165D, and S131V). Mouse CD80-WT protein is used as a positive control. 
         FIG. 31C  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CTLA4. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position 5131 (S131I, S131F, S131R, S131E, and S131Q). Mouse CD80-WT protein is used as a positive control. 
         FIG. 31D  depicts the binding assays by ELISA to test binding affinity of variant mouse CD80-Fc Fusion Proteins to immobilized binding partner mouse CTLA4. Types of variant mouse CD80 polypeptides tested herein are as follows: a single amino acid substitution/mutation at position S131 (S131A, and S131P). Mouse CD80-WT protein is used as a positive control. 
     
    
    
     DETAILED DESCRIPTION 
     All publications, patents and patent applications, including any drawings and appendices therein are incorporated by reference in their entirety for all purposes to the same extent as if each individual publication, patent or patent application, drawing, or appendix was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. 
     While various embodiments of the present disclosure are described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous modifications and changes to, and variations and substitutions of, the embodiments described herein will be apparent to those skilled in the art without departing from the disclosure. It is understood that various alternatives to the embodiments described herein may be employed in practicing the disclosure. It is also understood that every embodiment of the disclosure may optionally be combined with any one or more of the other embodiments described herein which are consistent with that embodiment. 
     Where elements are presented in list format (e.g., in a Markush group), it is understood that each possible subgroup of the elements is also disclosed, and any one or more elements can be removed from the list or group. 
     It is also understood that, unless clearly indicated to the contrary, in any method described or claimed herein that includes more than one act, the order of the acts of the method is not necessarily limited to the order in which the acts of the method are recited, but the disclosure encompasses embodiments in which the order is so limited. 
     It is further understood that, in general, where an embodiment in the description or the claims is referred to as comprising one or more features, the disclosure also encompasses embodiments that consist of, or consist essentially of, such feature(s). 
     It is also understood that any embodiment of the disclosure, e.g., any embodiment found within the prior art, can be explicitly excluded from the claims, regardless of whether or not the specific exclusion is recited in the specification. 
     Headings are included herein for reference and to aid in locating certain sections. Headings are not intended to limit the scope of the embodiments and concepts described in the sections under those headings, and those embodiments and concepts may have applicability in other sections throughout the entire disclosure. 
     I. Definitions 
     While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter. Unless defined otherwise, all terms of art, notations and other technical and scientific terms or terminology used herein are intended to have the same meaning as is commonly understood by one of ordinary skill in the art to which the claimed subject matter pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and/or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art. 
     The terms used throughout this specification are defined as follows unless otherwise limited in specific instances. As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms, acronyms, and abbreviations used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains. Unless indicated otherwise, abbreviations and symbols for chemical and biochemical names is per IUPAC-IUB nomenclature. Unless indicated otherwise, all numerical ranges are inclusive of the values defining the range as well as all integer values in-between. 
     The term “affinity modified” as used in the context of an immunoglobulin superfamily domain, means a mammalian immunoglobulin superfamily (IgSF) domain having an altered amino acid sequence (relative to the corresponding wild-type parental or unmodified IgSF domain) such that it has an increased or decreased binding affinity or avidity to at least one of its cognate binding partners (alternatively “counter-structures”) compared to the parental wild-type or unmodified (i.e., non-affinity modified) IgSF control domain. Included in this context is an affinity modified CD80 IgSF domain. In some embodiments, the affinity-modified IgSF domain can contain 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more amino acid differences, such as amino acid substitutions, in a wildtype or unmodified IgSF domain. An increase or decrease in binding affinity or avidity can be determined using well known binding assays such as flow cytometry. Larsen et al., American Journal of Transplantation, Vol 5: 443-453 (2005). See also, Linsley et al., Immunity, 1: 7930801 (1994). An increase in a protein&#39;s binding affinity or avidity to its cognate binding partner(s) is to a value at least 10% greater than that of the wild-type IgSF domain control and in some embodiments, at least 20%, 30%, 40%, 50%, 100%, 200%, 300%, 500%, 1000%, 5000%, or 10000% greater than that of the wild-type IgSF domain control value. A decrease in a protein&#39;s binding affinity or avidity to at least one of its cognate binding partner is to a value no greater than 90% of the control but no less than 10% of the wild-type IgSF domain control value, and in some embodiments no greater than 80%, 70% 60%, 50%, 40%, 30%, or 20% but no less than 10% of the wild-type IgSF domain control value. An affinity-modified protein is altered in primary amino acid sequence by substitution, addition, or deletion of amino acid residues. The term “affinity modified IgSF domain” is not be construed as imposing any condition for any particular starting composition or method by which the affinity-modified IgSF domain was created. Thus, the affinity modified IgSF domains of the present disclosure are not limited to wild type IgF domains that are then transformed to an affinity modified IgSF domain by any particular process of affinity modification. An affinity modified IgSF domain polypeptide can, for example, be generated starting from wild type mammalian IgSF domain sequence information, then modeled in silico for binding to its cognate binding partner, and finally recombinantly or chemically synthesized to yield the affinity modified IgSF domain composition of matter. In but one alternative example, an affinity modified IgSF domain can be created by site-directed mutagenesis of a wild-type IgSF domain. Thus, affinity modified IgSF domain denotes a product and not necessarily a product produced by any given process. A variety of techniques including recombinant methods, chemical synthesis, or combinations thereof, may be employed. 
     “Binding” as used herein (e.g. with reference to binding of a T-cell modulatory multimeric polypeptide of the present disclosure to a polypeptide (e.g., a T-cell receptor) on a T-cell) refers to a non-covalent interaction between. Binding interactions are generally characterized by a dissociation constant (KD) of less than 10′ M, less than 10 −7  M, less than 10 -8  M, less than 10 −9  M, less than 10 −10  M, less than 10 −11  M, less than 10 −12  M, less than 10 −13  M, less than 10 −14  M, or less than 10 −15  M. “Affinity” refers to the strength of binding, increased binding affinity being correlated with a lower KD. 
     The terms “binding affinity,” and “binding avidity” as used herein means the specific binding affinity and specific binding avidity, respectively, of a protein for its counter-structure under specific binding conditions. In biochemical kinetics, avidity refers to the accumulated strength of multiple affinities of individual non-covalent binding interactions, such as between CD80 and its counter structures CTLA-4, PD-L1 and/or CD28. As such, avidity is distinct from affinity, which describes the strength of a single interaction. An increase or attenuation in binding affinity of a variant CD80 containing an affinity modified CD80 IgSF domain to its counter-structure is determined relative to the binding affinity of the unmodified CD80, such as an unmodified CD80 containing the native or wild-type IgSF domain, such as IgV or IgC domain. Methods for determining binding affinity or avidity are known in art. See, for example, Larsen et al., American Journal of Transplantation, Vol 5: 443-453 (2005). In some embodiments, a variant CD80 of the disclosure (i.e. a CD80-Fc fusion protein containing an affinity modified IgSF domain) specifically binds to CTLA-4, PD-L1 and/or CD28 measured by flow cytometry with a binding affinity that yields a Mean Fluorescence Intensity (MFI) value at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% greater than a wild-type CD80 control in a binding assay. 
     The term “cognate binding partner” (used interchangeably with “counter-structure”) in reference to a polypeptide, such as in reference to an IgSF domain of a variant CD80, refers to at least one molecule (typically a native mammalian protein) to which the referenced polypeptide specifically binds under specific binding conditions. In some aspects, a variant CD80 containing an affinity modified IgSF domain specifically binds to the counter-structure of the corresponding native or wild-type CD80 but with increased or attenuated affinity. A species of ligand recognized and specifically binding to its cognate receptor under specific binding conditions is an example of a counter-structure or cognate binding partner of that receptor. A “cognate cell surface binding partner” is a cognate binding partner expressed on a mammalian cell surface. A “cell surface molecular species” is a cognate binding partner of ligands of the immunological synapse (IS), expressed on and by cells, such as mammalian cells, forming the immunological synapse. 
     As used herein, “conjugate,” “conjugation” or grammatical variations thereof refers the joining or linking together of two or more compounds resulting in the formation of another compound, by any joining or linking methods known in the art. It can also refer to a compound which is generated by the joining or linking together two or more compounds. For example, variant CD80 polypeptides linked directly or indirectly to one or more chemical moieties or polypeptide is an exemplary conjugate. Such conjugates include fusion proteins, those produced by chemical conjugates and those produced by any other methods. 
     The term “conservative amino acid substitution” as used herein means an amino acid substitution in which an amino acid residue is substituted by another amino acid residue having a side chain R group with similar chemical properties (e.g., charge or hydrophobicity). Examples of groups of amino acids that have side chains with similar chemical properties include 1) aliphatic side chains: glycine, alanine, valine, leucine, and isoleucine; 2) aliphatic-hydroxyl side chains: serine and threonine; 3) amide-containing side chains: asparagine and glutamine; 4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; 5) basic side chains: lysine, arginine, and histidine; 6) acidic side chains: aspartic acid and glutamic acid; and 7) sulfur-containing side chains: cysteine and methionine. Conservative amino acids substitution groups are: valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine, alanine-valine, glutamate-aspartate, and asparagine-glutamine. 
     “Co-stimulatory polypeptide,” as the term is used herein, includes a polypeptide on an antigen presenting cell (APC) (e.g., a dendritic cell, a B cell, and the like) that specifically binds a cognate co-stimulatory polypeptide on a T-cell, thereby providing a signal which, in addition to the primary signal provided by, for instance, binding of a TCR/CD3 complex with a major histocompatibility complex (MHC) polypeptide loaded with peptide, mediates a T-cell response, including, but not limited to, proliferation, activation, differentiation, and the like. 
     The terms “decrease” or “attenuate” “or suppress” as used herein means to decrease by a statistically significant amount. A decrease can be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. 
     The terms “derivatives” or “derivatized” refer to modification of a protein by covalently linking it, directly or indirectly, to a composition so as to alter such characteristics as biological half-life, bioavailability, immunogenicity, solubility, toxicity, potency, or efficacy while retaining or enhancing its therapeutic benefit. Derivatives of immunomodulatory polypeptides of the disclosure are within the scope of the present disclosure and can be made by, for example, glycosylation, pegylation, lipidation, or Fc-fusion. 
     As used herein, domain (typically a sequence of three or more, generally 5 or 7 or more amino acids, such as 10 to 200 amino acid residues) refers to a portion of a molecule, such as a protein or encoding nucleic acid, that is structurally and/or functionally distinct from other portions of the molecule and is identifiable. For example, domains include those portions of a polypeptide chain that can form an independently folded structure within a protein made up of one or more structural motifs and/or that is recognized by virtue of a functional activity, such as binding activity. A protein can have one, or more than one, distinct domains. For example, a domain can be identified, defined or distinguished by homology of the primary sequence or structure to related family members, such as homology to motifs. In another example, a domain can be distinguished by its function, such as an ability to interact with a biomolecule, such as a cognate binding partner. A domain independently can exhibit a biological function or activity such that the domain independently or fused to another molecule can perform an activity, such as, for example binding. A domain can be a linear sequence of amino acids or a non-linear sequence of amino acids. Many polypeptides contain a plurality of domains. Such domains are known, and can be identified by those of skill in the art. For exemplification herein, definitions are provided, but it is understood that it is well within the skill in the art to recognize particular domains by name. If needed appropriate software can be employed to identify domains. 
     The terms “effective amount” or “therapeutically effective amount” refer to a quantity and/or concentration of a therapeutic composition of the disclosure, including a protein composition or cell composition, that when administered ex vivo (by contact with a cell from a patient) or in vivo (by administration into a patient) either alone (i.e., as a monotherapy) or in combination with additional therapeutic agents, yields a statistically significant decrease in disease progression as, for example, by ameliorating or eliminating symptoms and/or the cause of the disease. An effective amount may be an amount that relieves, lessens, or alleviates at least one symptom or biological response or effect associated with a disease or disorder, prevents progression of the disease or disorder, or improves physical functioning of the patient. In the case of cell therapy, the effective amount is an effective dose or number of cells administered to a patient by adoptive cell therapy. In some embodiments the patient is a mammal such as a non-human primate or human patient. 
     The terms “enhanced” or “increased” as used herein in the context of increasing immunological activity of a mammalian lymphocyte means to increase one or more activities the lymphocyte. An increased activity can be one or more of increase cell survival, cell proliferation, cytokine production, or T-cell cytotoxicity, such as by a statistically significant amount. In some embodiments, reference to increased immunological activity means to induce IL-2 production in T-cell. In some embodiments, the immunological activity can be assessed by detection of IL-2 release. In some embodiments, reference to increased immunological activity means to increase interferon gamma (IFN-gamma) production, such as by a statistically significant amount. In some embodiments, the immunological activity can be assessed in a mixed lymphocyte reaction (MLR) assay. Methods of conducting MLR assays are known in the art. Wang et al., Cancer Immunol Res. 2014 September: 2(9):846-56. Other methods of assessing activities of lymphocytes are known in the art, including any assay as described herein. In some embodiments an enhancement can be an increase of at least 10%, 20%, 30%, 40%, 50%, 75%,100%, 200%, 300%, 400%, or 500% greater than a non-zero control value. 
     The term “engineered cell” as used herein refers to a mammalian cell that has been genetically modified by human intervention such as by recombinant DNA methods or viral transduction. In some embodiments, the cell is an immune cell, such as a lymphocyte (e.g. T-cell, B cell, NK cell) or an antigen presenting cell (e.g. dendritic cell). The cell can be a primary cell from a patient or can be a cell line. In some embodiments, an engineered cell of the disclosure comprises a variant CD80 of the disclosure engineered to modulate immunological activity of a T-cell expressing CD28, PD-L1, or CTLA-4 to which the variant CD80 specifically binds. In some embodiments, the variant CD80 is a transmembrane immunomodulatory protein (hereinafter referred to as “TIP”) containing the extracellular domain or a portion thereof containing the IgV and/or IgC domain linked to a transmembrane domain and, optionally, an intracellular signaling domain. In some cases, the TIP is formatted as a chimeric receptor containing a heterologous cytoplasmic signaling domain or endodomain. In some embodiments, an engineered cell is capable of expressing and secreting a immunomodulatory protein as described herein. Among provided engineered cells also are cells further containing an engineered T-cell receptor (TCR) or chimeric antigen receptor (CAR). 
     The term “engineered T-cell” as used herein refers to a T-cell such as a T helper cell, cytotoxic T-cell (alternatively, cytotoxic T lymphocyte or CTL), natural killer T-cell, regulatory T-cell, memory T-cell, or gamma delta T-cell, that has been genetically modified by human intervention such as by recombinant DNA methods or viral transduction methods. The term “engineered T-cell receptor” or “engineered TCR” refers to a T-cell receptor (TCR) engineered to specifically bind with a desired affinity to a major histocompatibility complex (MHC)/peptide target antigen that is selected, cloned, and/or subsequently introduced into a population of T-cells, often used for adoptive immunotherapy. In contrast to engineered TCRs, CARs are engineered to bind target antigens in a MHC independent manner. 
     The term “immunological synapse” or “immune synapse” as used herein generally refers to the natural interface between two interacting immune cells of an adaptive immune response including, e.g., the interface between an antigen-presenting cell (APC) or target cell and an effector cell, e.g., a lymphocyte, an effector T-cell, a natural killer cell, and the like. An immunological synapse between an APC and a T-cell is generally initiated by the interaction of a T-cell antigen receptor and major histocompatibility complex molecules, e.g., as described in Bromley et al., Annu Rev Immunol. 2001; 19:375-96; the disclosure of which is incorporated herein by reference in its entirety. 
     An Fc (fragment crystallizable) region or domain of an immunoglobulin molecule (also termed an Fc polypeptide) corresponds largely to the constant region of the immunoglobulin heavy chain, and is responsible for various functions, including the antibody&#39;s effector function(s). The Fc domain contains part or all of a hinge domain of an immunoglobulin molecule plus a CH2 and a CH3 domain. The Fc domain can form a dimer of two polypeptide chains joined by one or more disulfide bonds. In some embodiments, the Fc is a variant Fc that exhibits reduced (e.g. reduced greater than 30%, 40%, 50%, 60%, 70%, 80%, 90% or more) activity to facilitate an effector function. In some embodiments, reference to amino acid substitutions in an Fc region is by EU numbering system unless described with reference to a specific SEQ ID NO: EU numbering is known and is according to the most recently updated IMGT Scientific Chart (IMGT®, the international ImMunoGeneTics information system®, webpage at imgt.org/IMGTScientificChart/Numbering/Hu_IGHGnber.html and the EU index as reported in Kabat, E. A. et al. Sequences of Proteins of Immunological interest. 5th ed. US Department of Health and Human Services, NIH publication No. 91-3242 (1991). 
     An immunoglobulin Fc fusion (“Fc-fusion”), such as an immunomodulatory Fc fusion protein, is a molecule comprising one or more polypeptides (or one or more small molecules) operably linked to an Fc region of an immunoglobulin. An Fc-fusion may comprise, for example, the Fc region of an antibody (which facilitates effector functions and pharmacokinetics) and a variant CD80. An immunoglobulin Fc region may be linked indirectly or directly to one or more variant CD80 or small molecules (fusion partners). Various linkers are known in the art and can optionally be used to link an Fc to a fusion partner to generate an Fc-fusion. Fc-fusions of identical species can be dimerized to form Fc-fusion homodimers, or using non-identical species to form Fc-fusion heterodimers. In some embodiments, the Fc is a mammalian Fc such as a murine or human Fc. 
     A cell has been “genetically modified” or “transformed” or “transfected” by exogenous DNA, e.g. a recombinant expression vector, when such DNA has been introduced inside the cell. The presence of the exogenous DNA results in permanent or transient genetic change. The transforming DNA may or may not be integrated (covalently linked) into the genome of the cell. In prokaryotes, yeast, and mammalian cells, for example, the transforming DNA may be maintained on an episomal element such as a plasmid. With respect to eukaryotic cells, a stably transformed cell is one in which the transforming DNA has become integrated into a chromosome so that it is inherited by daughter cells through chromosome replication. 
     “Heterologous,” as used herein, means a nucleotide or polypeptide that is not found in the native nucleic acid or protein, respectively. 
     A “host cell,” as used herein, denotes an in vivo or in vitro eukaryotic cell or a cell from a multicellular organism (e.g., a cell line) cultured as a unicellular entity, which eukaryotic cells can be, or have been, used as recipients for a nucleic acid (e.g., an expression vector that comprises a nucleotide sequence encoding a multimeric polypeptide of the present disclosure), and include the progeny of the original cell which has been genetically modified by the nucleic acid. It is understood that the progeny of a single cell may not necessarily be completely identical in morphology or in genomic or total DNA complement as the original parent, due to natural, accidental, or deliberate mutation. The term “host cell” refers to a cell that can be used to express a protein encoded by a recombinant expression vector. A host cell can be a prokaryote, for example, E. coli, or it can be a eukaryote, for example, a single-celled eukaryote (e.g., a yeast or other fungus), a plant cell (e.g., a tobacco or tomato plant cell), an animal cell (e.g., a human cell, a monkey cell, a hamster cell, a rat cell, a mouse cell, or an insect cell) or a hybridoma. Examples of host cells include Chinese hamster ovary (CHO) cells or their derivatives such as Veggie CHO and related cell lines which grow in serum-free media or CHO strain DX-B 11, which is deficient in DHFR. In some embodiments, a host cell is a mammalian cell (e.g., a human cell, a monkey cell, a hamster cell, a rat cell, a mouse cell, or an insect cell). 
     The term “immunoglobulin” (abbreviated “Ig”) as used herein refers to a mammalian immunoglobulin protein including any of the five human classes of antibody: IgA (which includes subclasses IgAl and IgA2), IgD, IgE, IgG (which includes subclasses IgG1, IgG2, IgG3, and IgG4), and IgM. The term is also inclusive of immunoglobulins that are less than full-length, whether wholly or partially synthetic (e.g., recombinant or chemical synthesis) or naturally produced, such as antigen binding fragment (Fab), variable fragment (Fv) containing VH and VL, the single chain variable fragment (scFv) containing VH and VL linked together in one chain, as well as other antibody V region fragments, such as Fab&#39;, F(ab)2, F(ab&#39;)2, dsFv diabody, Fc, and Fd polypeptide fragments. Bispecific antibodies, homobispecific and heterobispecific, are included within the meaning of the term. 
     The term “immunoglobulin superfamily” or “IgSF” as used herein means the group of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily based on shared structural features with immunoglobulins (i.e., antibodies); they all possess a domain known as an immunoglobulin domain or fold. Members of the IgSF include cell surface antigen receptors, co-receptors and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors and intracellular muscle proteins. They are commonly associated with roles in the immune system. Proteins in the immunological synapse are often members of the IgSF. IgSF can also be classified into “subfamilies” based on shared properties such as function. Such subfamilies typically consist of from 4 to 30 IgSF members. 
     The terms “IgSF domain” or “immunoglobulin domain” or “Ig domain” as used herein refers to a structural domain of IgSF proteins. Ig domains are named after the immunoglobulin molecules. They contain about 70-110 amino acids and are categorized according to their size and function. Ig-domains possess a characteristic Ig-fold, which has a sandwich-like structure formed by two sheets of antiparallel beta strands. Interactions between hydrophobic amino acids on the inner side of the sandwich and highly conserved disulfide bonds formed between cysteine residues in the B and F strands, stabilize the Ig-fold. One end of the Ig domain has a section called the complementarity determining region that is important for the specificity of antibodies for their ligands. The Ig like domains can be classified (into classes) as: IgV, IgC1, IgC2, or IgI. Most Ig domains are either variable (IgV) or constant (IgC). IgV domains with 9 beta strands are generally longer than IgC domains with 7 beta strands. Ig domains of some members of the IgSF resemble IgV domains in the amino acid sequence, yet are similar in size to IgC domains. These are called IgC2 domains, while standard IgC domains are called IgC1 domains. T-cell receptor (TCR) chains contain two Ig domains in the extracellular portion; one IgV domain at the N-terminus and one IgC1 domain adjacent to the cell membrane. CD80 contains two Ig domains: IgV and IgC. 
     The term “IgSF species” as used herein means an ensemble of IgSF member proteins with identical or substantially identical primary amino acid sequence. Each mammalian immunoglobulin superfamily (IgSF) member defines a unique identity of all IgSF species that belong to that IgSF member. Thus, each IgSF family member is unique from other IgSF family members and, accordingly, each species of a particular IgSF family member is unique from the species of another IgSF family member. Nevertheless, variation between molecules that are of the same IgSF species may occur owing to differences in post-translational modification such as glycosylation, phosphorylation, ubiquitination, nitrosylation, methylation, acetylation, and lipidation. Additionally, minor sequence differences within a single IgSF species owing to gene polymorphisms constitute another form of variation within a single IgSF species as do wild type truncated forms of IgSF species owing to, for example, proteolytic cleavage. A “cell surface IgSF species” is an IgSF species expressed on the surface of a cell, generally a mammalian cell. 
     An “immunomodulatory polypeptide” is a polypeptide that modulates immunological activity. By “modulation” or “modulating” an immune response is meant that immunological activity is either increased or decreased. An immunomodulatory polypeptide can be a single polypeptide chain or a multimer (dimers or higher order multimers) of at least two polypeptide chains covalently bonded to each other by, for example, interchain disulfide bonds. Thus, monomeric, dimeric, and higher order multimeric polypeptides are within the scope of the defined term. Multimeric polypeptides can be homomultimeric (of identical polypeptide chains) or heteromultimeric (of non-identical polypeptide chains). An immunomodulatory polypeptide of the disclosure comprises a variant CD80. 
     The terms “individual,” “subject,” “host,” and “patient,” are used interchangeably herein and refer to any mammalian subject for whom diagnosis, treatment, or therapy is desired. Mammals include, e.g., humans, non-human primates, rodents (e.g., rats; mice), lagomorphs (e.g., rabbits), ungulates (e.g., cows, sheep, pigs, horses, goats, and the like), etc. 
     The term “lymphocyte” as used herein means any of three subtypes of white blood cell in a mammalian immune system. They include natural killer cells (NK cells) (which function in cell-mediated, cytotoxic innate immunity), T-cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). T-cells include: T helper cells, cytotoxic T-cells, natural killer T-cells, memory T-cells, regulatory T-cells, or gamma delta T-cells. Innate lymphoid cells (ILC) are also included within the definition of lymphocyte. 
     The terms “mammal,” or “patient” specifically includes reference to at least one of a: human, chimpanzee, rhesus monkey, cynomolgus monkey, dog, cat, mouse, or rat.A “modulatory domain” or “immunomodulatory domain” of a T-cell modulatory multimeric polypeptide of the present disclosure comprises a co-stimulatory polypeptide. 
     The terms “modulating” or “modulate” as used herein in the context of an immune response, such as a mammalian immune response, refer to any alteration, such as an increase or a decrease, of existing or potential immune responses that occurs as a result of administration of an immunomodulatory polypeptide comprising a variant CD80 of the present disclosure or as a result of administration of engineered cells expresses an immunomodulatory protein, such as a variant CD80 transmembrane immunomodulatory protein of the present disclosure. Thus, it refers to an alteration, such as an increase or decrease, of an immune response as compared to the immune response that occurs or is present in the absence of the administration of the immunomodulatory protein comprising the variant CD80 or cells expressing such an immunomodulatory polypeptide. Such modulation includes any induction, activation, suppression or alteration in degree or extent of immunological activity of an immune cell. Immune cells include B cells, T-cells, NK (natural killer) cells, NK T-cells, professional antigen-presenting cells (APCs), and non-professional antigen-presenting cells, and inflammatory cells (neutrophils, macrophages, monocytes, eosinophils, and basophils). Modulation includes any change imparted on an existing immune response, a developing immune response, a potential immune response, or the capacity to induce, regulate, influence, or respond to an immune response. Modulation includes any alteration in the expression and/or function of genes, proteins and/or other molecules in immune cells as part of an immune response. Modulation of an immune response or modulation of immunological activity includes, for example, the following: elimination, deletion, or sequestration of immune cells; induction or generation of immune cells that can modulate the functional capacity of other cells such as autoreactive lymphocytes, antigen presenting cells, or inflammatory cells; induction of an unresponsive state in immune cells (i.e., anergy); enhancing or suppressing the activity or function of immune cells, including but not limited to altering the pattern of proteins expressed by these cells. Examples include altered production and/or secretion of certain classes of molecules such as cytokines, chemokines, growth factors, transcription factors, kinases, costimulatory molecules, or other cell surface receptors or any combination of these modulatory events. Modulation can be assessed, for example, by an alteration of a binding affinity and/or avidity of a variant CD80 to counter structures CTLA-4, PD-L1 or CD28. Modulation can be assessed, for example, by an alteration in IL-2 expression or release in T-cells relative to the wild-type CD80 control. Modulation can be assessed, for example, by an alteration in IFN-gamma (interferon gamma) expression relative to the wild-type CD80 control in a primary T-cell assay (see, Zhao and Ji, Exp Cell Res. 2016 Jan. 1; 340(1) 132-138). Modulation can be assessed, for example, by an alteration of an immunological activity of engineered cells, such as an alteration in in cytotoxic activity of engineered cells or an alteration in cytokine secretion of engineered cells relative to cells engineered with a wild-type CD80 transmembrane protein. 
     The terms “polynucleotide” and “nucleic acid,” used interchangeably herein, refer to a polymeric form of nucleotides of any length, either ribonucleotides or deoxyribonucleotides. Thus, this term includes, but is not limited to, single-, double-, or multi-stranded DNA or RNA, genomic DNA, cDNA, DNA-RNA hybrids, or a polymer comprising purine and pyrimidine bases or other natural, chemically or biochemically modified, non-natural, or derivatized nucleotide bases. Unless specifically limited, the terms encompass nucleic acids containing known analogues of natural nucleotides and that have similar binding properties to it and are metabolized in a manner similar to naturally-occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary nucleotide sequences as well as the sequence explicitly indicated (a “reference sequence”). Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues. The term nucleic acid or polynucleotide encompasses cDNA or mRNA encoded by a gene. 
     The terms “peptide,” “polypeptide,” and “protein” are used interchangeably herein, and refer to a polymeric form of amino acids of any length, which can include coded and non-coded amino acids, chemically or biochemically modified or derivatized amino acids, and polypeptides having modified peptide backbones. The terms include post-translational modifications of the polypeptide, for example, glycosylations, acetylations, sialylations, phosphorylations and the like. The terms also include molecules in which one or more amino acid analogs or non-canonical or unnatural amino acids are included as can be synthesized, or expressed recombinantly using known protein engineering techniques. In addition, proteins can be derivatized. 
     A polynucleotide or polypeptide has a certain percent “sequence identity” to another polynucleotide or polypeptide, meaning that, when aligned, that percentage of bases or amino acids are the same, and in the same relative position, when comparing the two sequences. Sequence identity can be determined in a number of different ways. To determine sequence identity, sequences can be aligned using various convenient methods and computer programs (e.g., BLAST, T-COFFEE, MUSCLE, MAFFT, etc.), available over the world wide web at sites including ncbi.nlm.nili. gov/BLAST, ebi.ac.uk/Tools/msa/tcoffee/, ebi.ac.uk/Tools/msa/muscle/, mafft.cbrc.jp/alignment/software/. See, e.g., Altschul et al. (1990), J. Mol. Bioi. 215:403-10. 
     “Recombinant,” as used herein, means that a particular nucleic acid (DNA or RNA) is the product of various combinations of cloning, restriction, polymerase chain reaction (PCR) and/or ligation steps resulting in a construct having a structural coding or non-coding sequence distinguishable from endogenous nucleic acids found in natural systems. DNA sequences encoding polypeptides can be assembled from cDNA fragments or from a series of synthetic oligonucleotides, to provide a synthetic nucleic acid which is capable of being expressed from a recombinant transcriptional unit contained in a cell or in a cell-free transcription and translation system. For example, a “recombinant nucleic acid” is one that is made by recombining nucleic acids, e.g., during cloning, affinity modification, DNA shuffling or other well-known molecular biological procedures. A “recombinant DNA molecule,” is comprised of segments of DNA joined together by means of such molecular biological techniques. The term “recombinant protein” or “recombinant polypeptide” as used herein refers to a protein molecule which is expressed using a recombinant DNA molecule. A “recombinant host cell” is a cell that contains and/or expresses a recombinant nucleic acid or that is otherwise altered by genetic engineering, such as by introducing into the cell a nucleic acid molecule encoding a recombinant protein, such as a transmembrane immunomodulatory protein provided herein. For example, a genetically modified eukaryotic host cell is genetically modified by virtue of introduction into a suitable eukaryotic host cell a heterologous nucleic acid, e.g., an exogenous nucleic acid that is foreign to the eukaryotic host cell, or a recombinant nucleic acid that is not normally found in the eukaryotic host cell. Transcriptional control signals in eukaryotes comprise “promoter” and “enhancer” elements. Promoters and enhancers consist of short arrays of DNA sequences that interact specifically with cellular proteins involved in transcription. Promoter and enhancer elements have been isolated from a variety of eukaryotic sources including genes in yeast, insect and mammalian cells and viruses (analogous control elements, i.e., promoters, are also found in prokaryotes). The selection of a particular promoter and enhancer depends on what cell type is to be used to express the protein of interest. The terms “in operable combination,” “in operable order” and “operably linked” as used herein refer to the linkage of nucleic acid sequences in such a manner or orientation that a nucleic acid molecule capable of directing the transcription of a given gene and/or the synthesis of a desired protein molecule is produced. 
     The terms “recombinant expression vector,” or “DNA construct” are used interchangeably herein to refer to a DNA molecule comprising a vector and one insert. Recombinant expression vectors are usually generated for the purpose of expressing and/or propagating the insert(s) and/or the expression cassette, or for the construction of other recombinant nucleotide sequences. The recombinant expression vector refers to a DNA molecule containing a desired coding sequence and appropriate nucleic acid sequences necessary for the expression of the operably linked coding sequence in a particular host cell. Nucleic acid sequences necessary for expression in prokaryotes include a promoter, optionally an operator sequence, a ribosome binding site and possibly other sequences. Eukaryotic cells are known to utilize promoters, enhancers, and termination and polyadenylation signals. A secretory signal peptide sequence can also, optionally, be encoded by the recombinant expression vector, operably linked to the coding sequence for the recombinant protein, such as a recombinant fusion protein, so that the expressed fusion protein can be secreted by the recombinant host cell, for easier isolation of the fusion protein from the cell, if desired. The term includes the vector as a self-replicating nucleic acid structure as well as the vector incorporated into the genome of a host cell into which it has been introduced. Among the vectors are viral vectors, such as lentiviral vectors. 
     “T-cell” includes all types of immune cells expressing CD3, including T-helper cells (CD4+ cells), cytotoxic T-cells (CD8+ cells), T-regulatory cells (Treg), and NK-T-cells. 
     The terms “treatment”, “treating” and the like are used herein to generally mean obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease or symptom thereof and/or may be therapeutic in terms of a partial or complete cure for a disease and/or adverse effect attributable to the disease. “Treatment” as used herein covers any treatment of a disease or symptom in a mammal, and includes: (a) preventing the disease or symptom from occurring in a subject which may be predisposed to acquiring the disease or symptom but has not yet been diagnosed as having it; (b) inhibiting the disease or symptom, i.e., arresting its development; or (c) relieving the disease, i.e., causing regression of the disease. The therapeutic agent may be administered before, during or after the onset of disease or injury. The treatment of ongoing disease, where the treatment stabilizes or reduces the undesirable clinical symptoms of the patient, is of particular interest. Such treatment is desirably performed prior to complete loss of function in the affected tissues. The subject therapy can desirably be administered during the symptomatic stage of the disease, and in some cases after the symptomatic stage of the disease. . “Treating,” “treatment,” or “therapy” also means a decrease in the severity of symptoms in an acute or chronic disease or disorder or a decrease in the relapse rate as for example in the case of a relapsing or remitting autoimmune disease course or a decrease in inflammation in the case of an inflammatory aspect of an autoimmune disease. As used herein in the context of cancer, the terms “treatment” or, “inhibit,” “inhibiting” or “inhibition” of cancer refers to at least one of: a statistically significant decrease in the rate of tumor growth, a cessation of tumor growth, or a reduction in the size, mass, metabolic activity, or volume of the tumor, as measured by standard criteria such as, but not limited to, the Response Evaluation Criteria for Solid Tumors (RECIST), or a statistically significant increase in progression free survival (PFS) or overall survival (OS). “Preventing,” “prophylaxis,” or “prevention” of a disease or disorder as used in the context of this disclosure refers to the administration of an immunomodulatory polypeptide or engineered cells of the disclosure, either alone or in combination with another compound, to prevent the occurrence or onset of a disease or disorder or some or all of the symptoms of a disease or disorder or to lessen the likelihood of the onset of a disease or disorder. 
     The term “variant” (also “mutant”, “mutated” or “modified”) as used in reference to a variant CD80 means a CD80, such as a mammalian (e.g., human or murine) CD80 created by human intervention. The variant CD80 is a polypeptide having an altered amino acid sequence, relative to an unmodified or wild-type CD80. The variant CD80 is a polypeptide which differs from a wild-type CD80 isoform sequence by one or more amino acid substitutions, deletions, additions, or combinations thereof. For purposes herein, the variant CD80 contains at least one affinity modified domain, whereby one or more of the amino acid differences occurs in an IgSF domain (e.g. IgC domain and/or IgV domain). A variant CD80 can contain 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more amino acid differences, such as amino acid substitutions. The variant CD80 polypeptides generally exhibit at least 50%, 60%, 70%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to a wild-type or unmodified CD80 extracellular domain (SEQ ID NO: 1). Non-naturally occurring amino acids as well as naturally occurring amino acids are included within the scope of permissible substitutions or additions. A variant CD80 is not limited to any particular method of making and includes, for example, de novo chemical synthesis, de novo recombinant DNA techniques, or combinations thereof. A variant CD80 of the disclosure specifically binds to at least one or more of: CD28, PD-L1, or CTLA-4 of a mammalian species . In some embodiments, the altered amino acid sequence results in an altered (i.e., increased or decreased) binding affinity or avidity to CD28, PD-L1, or CTLA-4 compared to the wild-type CD80 protein. An increase or decrease in binding affinity or avidity can be determined using well known binding assays such as flow cytometry. Larsen et al., American Journal of Transplantation, Vol 5: 443-453 (2005). See also, Linsley et al., Immunity, 1: 7930801 (1994). An increase in variant CD80 binding affinity or avidity to CD28, PD-L1, or CTLA-4 is to a value at least 5% greater than that of the wild-type CD80 control value and in some embodiments, at least 10%, 15%, 20%, 30%, 40%, 50%, 100% greater than that of the wild-type CD80 control value. A decrease in CD80 binding affinity or avidity to CD28, PD-L1, or CTLA-4 is to a value no greater than 95% of the of the wild-type CD80 control value, and in some embodiments no greater than 80%, 70% 60%, 50%, 40%, 30%, 20%, 10%, 5%, or no detectable binding affinity or avidity of the wild-type CD80 control value. A variant CD80 is altered in primary amino acid sequence by substitution, addition, or deletion of amino acid residues. The term “variant” in the context of variant CD80 is not be construed as imposing any condition for any particular starting composition or method by which the variant CD80 is created. A variant CD80 can, for example, be generated starting from wild type mammalian CD80 sequence information, then modeled in silico for binding to CD28, PD-L1, or CTLA-4, and finally recombinantly or chemically synthesized to yield a variant CD80 of the present disclosure. In alternative embodiment, a variant CD80 can be created by site-directed mutagenesis of a wild-type CD80. Thus, variant CD80 denotes a composition and not necessarily a product produced by any given process. A variety of techniques including recombinant methods, chemical synthesis, or combinations thereof, may be employed. 
     Before the present disclosure is further described, it is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims. 
     Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. 
     It must be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a multimeric polypeptide” includes a plurality of such multimeric polypeptides and reference to “the modulatory domain” includes reference to one or more modulatory domains and equivalents thereof known to those skilled in the art, and so forth. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. 
     It is appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. All combinations of the embodiments pertaining to the disclosure are specifically embraced by the present disclosure and are disclosed herein just as if each and every combination was individually and explicitly disclosed. In addition, all sub-combinations of the various embodiments and elements thereof are also specifically embraced by the present disclosure and are disclosed herein just as if each and every such sub-combination was individually and explicitly disclosed herein. 
     The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
     II. Variant CD80 Polypeptides 
     The present disclosure provides variant CD80 polypeptides that exhibit altered (increased or decreased) binding activity or affinity for one or more of a CD80 cognate binding partner. In some embodiments, the CD80 cognate binding partner is CD28, PD-L1, or CTLA-4. In some embodiments, the variant CD80 polypeptide contains one or more amino acids modifications, such as one or more substitutions (alternatively, “mutations” or “replacements”), deletions or addition, in an immunoglobulin superfamily (IgSF) domain (IgD) relative to a wild-type or unmodified CD80 polypeptide or a portion of a wild-type or unmodified CD80 containing an immunoglobulin superfamily (IgSF) domain or a specific binding fragment thereof Thus, a provided variant CD80 polypeptide is or comprises a variant IgD (hereinafter called “vIgD”) in which the one or more amino acid modifications (e.g. substitutions) is in an IgD. 
     In some embodiments, the IgD comprises an IgC domain or an IgV domain or specific binding fragment of the IgC domain or the IgV domain, or combinations thereof. In some embodiments, the IgD can be an IgC only, the combination of the IgC and IgV, including the entire extracellular domain (ECD), or any combination of Ig domains of CD80. Table 1 provides exemplary residues that correspond to the IgC domain of CD80. 
     The IgC domain of CD80 does not directed interact with CD80&#39;s binding partners. The present inventors employed structural-based rational design to select positions within the IgC domain of CD80 for mutagenesis. These selected positions are located near the interdomain between the IgV and IgC and are in the vicinity of the flexible hinge region. Mutations in this region could potentially force changes in the IgC&#39;s tertiary structure and hence affect CD80 dimer configuration. 
     The present inventors choose to mutate amino-acid residues in the IgC domain which does not directly interacts with the target proteins upon binding. They rationally designed mutations in the IgC domain that would alter the conformation and/or the dynamics of the whole mutant protein, and then through which, to modulate its binding affinities towards the target proteins and/or its biological functions when interacting with the target proteins, for example, to modulate the function of the mutant protein towards CD28 activation. Through this approach, the present inventors achieved selectively changing the binding affinity or function of the CD80 protein with the selected target protein while leaving the interaction with one of another target protein or the other two target proteins minimally affected. For example, through rational design, the present inventors have obtained mutants that have a range of activity towards CD28 activation while maintaining similar binding affinity towards CTLA-4. For example, A165F had very low CD28 activation compared to wt CD80, yet its binding affinity towards CTLA-4 (binding assay by FACS, EC50 =0.046 uM vs EC50 =0.014 uM wt CD80) and PD-L1 (ELISA assay, EC50=0.38 uM vs EC50=0.98 uM wt CD80) were similar; S131I had similar CD28 activation (IL-2 release assay, EC50=1.13 uM vs EC50=0.94 uM wt CD80) and binding affinity towards CTLA-4 (binding assay by FACS, EC50=0.028 uM vs EC50=0.014 uM wt CD80) compared to wt CD80, yet its binding affinity towards PD-L1 was four-fold higher than the wt CD80 (ELISA assay, EC50=0.24 uM vs EC50=0.98 uM wt CD80). 
     In some embodiments, the variant is modified in one more IgSF domains relative to the sequence of an unmodified CD80 sequence. In some embodiments, the unmodified CD80 sequence is a wild-type CD80. In some embodiments, the unmodified or wild-type CD80 has the sequence of a native CD80 or an ortholog thereof. In some embodiments, the unmodified CD80 is or comprises the extracellular domain (ECD) of CD80 or a portion thereof containing one or more IgSF domain. In some embodiments, the extracellular domain of an unmodified or wild-type CD80 polypeptide comprises an IgC domain and/or an IgV domain. However, the variant CD80 polypeptide need not comprise both the IgC domain and the IgV domain. In some embodiments, the variant CD80 polypeptide comprises or consists essentially of the IgC domain or a specific binding fragment thereof. In some embodiments, the variant CD80 polypeptide comprises or consists essentially of the IgV domain or specific binding fragments thereof. In some embodiments, the variant CD80 is soluble and lacks a transmembrane domain. In some embodiments, the variant CD80 further comprises a transmembrane domain and, in some cases, also a cytoplasmic domain. 
     In some embodiments, the wild-type or unmodified CD80 sequence is a mammalian CD80 sequence. In some embodiments, the wild-type or unmodified CD80 sequence can be a mammalian CD80 that includes, but is not limited to, human, mouse, cynomolgus monkey, or rat. In some embodiments, the wild-type or unmodified CD80 sequence is human. 
     In some embodiments, variant CD80 polypeptides comprise an amino acid sequence having at least 80% amino acid sequence identity to SEQ ID NO: 1, wherein the variant CD80 polypeptide comprises one or more of the amino acid substitution modifications compared to SEQ ID NO: 1, wherein the one or more substitution modifications are at positions 131, 139, 155, 165, or 166 of SEQ ID NO: 1. In some embodiments, the amino acid substitution modification is any of the 20 amino acids other than the corresponding wild type amino acid in SEQ ID NO: 1. 
     The variant CD80 polypeptides generally exhibit at least 50%, 60%, 70%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to a corresponding wild-type or unmodified CD80, a mature sequence thereof or a portion thereof containing the extracellular domain or an IgSF domain thereof set forth in SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptides exhibit at least 50%, 60%, 70%, 80%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more sequence identity to a corresponding wild-type or unmodified CD80 comprising the sequence set forth in SEQ ID NO: 1. 
     In some embodiments, the specific binding fragment of the IgC domain contains an amino acid sequence that has at least about 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% sequence identity to of a corresponding wild-type or unmodified IgC domain. 
     In some embodiments, the specific binding fragment of the IgV domain contains an amino acid sequence that has at least about 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% sequence identity to of a corresponding wild-type or unmodified IgV domain. 
     In any of such embodiments, the one or more amino acid modifications (e.g. substitutions) of the variant CD80 polypeptides can be located in any one or more of the CD80 polypeptide domains. For example, in some embodiments, one or more amino acid substitutions are located in the extracellular domain of the variant CD80 polypeptide. In some embodiments, one or more amino acid substitutions are located in the IgC domain or specific binding fragment of the IgC domain. In some embodiments, one or more amino acid modifications (e.g. substitutions) are located in the IgV domain or specific binding fragment of the IgV domain. 
     In other embodiments, the variant CD80 polypeptide further comprises a second polypeptide that is capable of dimerizing. In some embodiments, the second polypeptide is an immunoglobulin Fc domain. In some embodiments, the immunoglobulin Fc domain is a human IgG1 Fc domain, a human IgG2 Fc domain, a human IgG3 Fc domain, or a human IgG4 Fc domain. In some embodiments, the immunoglobulin Fc domain is a mouse IgG1 Fc domain, a mouse IgG2a Fc domain, a mouse IgG2b Fc domain, or a mouse IgG3 Fc domain. In some embodiments, the variant CD80 polypeptide further comprises a therapeutically active moiety. 
     In some embodiments, provided herein is a polynucleotide encoding the variant CD80 polypeptide of the present disclosure. In some embodiments, the polynucleotide is a synthetic nucleic acid. In some embodiments, the polynucleotide is cDNA. In some embodiments, the polynucleotide is operably linked to a transcriptional control element. In some embodiments, the transcriptional control element is a promoter that is functional in a eukaryotic cell. 
     In other embodiments, provided herein is a vector comprising the polynucleotide of the present disclosure. In some embodiments, the vector is an expression vector. In some embodiments, the vector is a mammalian vector or a viral vector. 
     Generally, each of the various attributes of polypeptides are separately disclosed below (e.g., soluble, secretable and membrane bound polypeptides, affinity of CD80 for CD28, PD-L1, and CTLA-4, number of variations per polypeptide chain, number of linked polypeptide chains, the number and nature of amino acid alterations per variant CD80, etc.). However, as will be clear to the skilled artisan, any particular polypeptide can comprise a combination of these independent attributes. It is understood that reference to amino acids, including to a specific sequence set forth as a SEQ ID NO used to describe domain organization of an IgSF domain are for illustrative purposes and are not meant to limit the scope of the embodiments provided. It is understood that polypeptides and the description of domains thereof are theoretically derived based on homology analysis and alignments with similar molecules. Thus, the exact locus can vary, and is not necessarily the same for each protein. Hence, the specific IgSF domain, such as specific IgC domain or IgV domain, can be several amino acids (such as one, two, three or four) longer or shorter. 
     Further, various embodiments of the disclosure as discussed below are frequently provided within the meaning of a defined term as disclosed above. The embodiments described in a particular definition are therefore to be interpreted as being incorporated by reference when the defined term is utilized in discussing the various aspects and attributes described herein. Thus, the headings, the order of presentation of the various aspects and embodiments, and the separate disclosure of each independent attribute is not meant to be a limitation to the scope of the present disclosure. 
     Exemplary Modifications 
     In some embodiments, the amino acid substitution modification at position 131 of SEQ ID NO: 1 is S131A, S131V, S131I, S131F, S131R, S131E, S131D, or S131Q. In some embodiments, the amino acid substitution modification at position 139 of SEQ ID NO: 1 is L139V.In some embodiments, the amino acid substitution modification at position 155 of SEQ ID NO: 1 is V155A, V1551, or V155T. In some embodiments, the amino acid substitution modification at position 165 of SEQ ID NO: 1 is A165S, A165V, A1651, A165F, A165R, A165E, A165D, or A165Q. In some embodiments, the amino acid substitution modification at position 166 of SEQ ID NO: 1 is V166A, V166L, or V166T. 
     In some embodiments, the variant CD80 polypeptide comprises two or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the two or more substitution modifications are at positions 130, 131, 139, 155, 156, 165, or 166 of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications V166L and L139V. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications S156A and V155A. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications S156A and V1551. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications S156A and V155T. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications S156A and T130A. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications S156A and V166A. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications 51561 and A165S. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications 51561 and S131A. In some embodiments, the variant CD80 polypeptide comprises two amino acid substitution modifications A165S and S131A. 
     In some embodiments, the variant CD80 polypeptide comprises three or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the three or more substitution modifications are at positions 130, 131, 139, 155, 156, 165, or 166 of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises three amino acid substitution modifications S156A, V166L and L139V. In some embodiments, the variant CD80 polypeptide comprises three amino acid substitution modifications 51561, A165S and S131A. 
     In some embodiments, the variant CD80 polypeptide comprises four or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the four or more substitution modifications are at positions 130, 131, 139, 155, 156, 165, or 166 of SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide comprises five or more of the amino acid substitution modifications compared to SEQ ID NO: 1, and wherein the five or more substitution modifications are at positions 130, 131, 139, 155, 156, 165, or 166 of SEQ ID NO: 1. 
     In some embodiments, the variant CD80 polypeptide has increased or decreased binding affinity for CTLA-4 compared to SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide has increased or decreased binding affinity for CD28 compared to SEQ ID NO: 1. In some embodiments, the variant CD80 polypeptide has increased or decreased binding affinity for PD-L1 compared to SEQ ID NO: 1. 
     In some embodiments, a variant CD80 polypeptide of the disclosure is sialylated. 
     Provided herein are variant CD80 polypeptides containing at least one affinity-modified IgSF domain (e.g. IgC or IgV) or a specific binding fragment thereof in an IgSF domain contained in a wild-type or unmodified CD80 polypeptide such that the variant CD80 polypeptide exhibits altered (increased or decreased) binding activity or affinity for one or more ligands CD28, PD-L1, or CTLA-4 compared to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptides have a binding affinity for CD28, PD-L1, and/or CTLA-4 that differs from that of a wild-type or unmodified CD80 polypeptide control sequence as determined by, for example, solid-phase ELISA immunoassays, flow cytometry or Biacore assays. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28, PD-L1, and/or CTLA-4. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28, PD-L1, and/or CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. The CD28, PD-L1, and/or the CTLA-4 can be a mammalian protein, such as a human protein or a murine protein. 
     Binding affinities for each of the cognate binding partners are generally independent; that is, in some embodiments, the variant CD80 polypeptide has an increased binding affinity for one, two or three of CD28, PD-L1, and/or CTLA-4, and a decreased binding affinity for one, two or three of CD28, PD-L1, and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and a decreased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28 and PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28 and an increased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and a decreased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28 and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28 and an increased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for PD-L1 and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for PD-L1 and a decreased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for PD-L1 and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for PD-L1 and an increased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28, PD-L1, and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28, PD-L1, and CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and PD-L1, and a decreased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has a decreased binding affinity for CD28 and PD-L1, and an increased binding affinity for CTLA-4, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for CD28 and CTLA-4, and a decreased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an decreased binding affinity for CD28 and CTLA-4, and an increased binding affinity for PD-L1, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an increased binding affinity for PD-L1 and CTLA-4, and a decreased binding affinity for CD28, relative to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide has an decreased binding affinity for PD-L1 and CTLA-4, and an increased binding affinity for CD28, relative to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to CD28, PD-L1, and/or CTLA-4 exhibit an increase in binding affinity relative to the wild-type or unmodified CD80 polypeptide control of at least about 5%, such as at least about 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more for the CD28, PD-L1, and/or CTLA-4. In some embodiments, the increase in binding affinity relative to the wild-type or unmodified CD80 polypeptide is more than 1.2-fold, 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, 20-fold, 30-fold, 40-fold or 50-fold. In such examples, the wild-type or unmodified CD80 polypeptide has the same sequence as the variant CD80 polypeptide except that it does not contain the one or more amino acid modifications (e.g. substitutions). 
     In some embodiments, variant CD80 polypeptides with reduced or decreased binding affinity to CD28, PD-L1, and/or CTLA-4 have decrease in binding affinity relative to the wild-type or unmodified CD80 polypeptide control of at least 5%, such as at least about 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more for the CD28, PD-L1, and/or CTLA-4. In some embodiments, the decrease in binding affinity relative to the wild-type or unmodified CD80 polypeptide is more than 1.2-fold, 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, 20-fold, 30-fold 40-fold or 50-fold. In such examples, the wild-type or unmodified CD80 polypeptide has the same sequence as the variant CD80 polypeptide except that it does not contain the one or more amino acid modifications, e.g. substitutions. 
     In some embodiments, the equilibrium dissociation constant (Kd) of any of the foregoing embodiments to CD28, PD-L1, and/or CTLA-4 can be less than 1×10 −5  M, 1×10 −6  M, 1×10 −7  M, 1×10 −8 M, 1×10 −9  M, 1×10 −10  M or 1×10 −11  M, or 1×10 −12  M. 
     In some embodiments, variant CD80 polypeptides have an increased or greater binding affinity to CD28. In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to CD28 have an increase in binding affinity relative to the wild-type or unmodified CD80 polypeptide control of at least about 5%, such as at least about 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more for CD28. In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to CD28 have an equilibrium dissociation constant (Kd) of less than 200 pM, 300 pM, 400 pM, 500 pM, or 600 pM for CD28. In some embodiments, the variant polypeptide specifically binds to the ectodomain of one of CD28 with increased selectivity compared to the unmodified CD80. In some embodiments, the increased selectivity is for CD28. 
     In some embodiments, variant CD80 polypeptides have an increased or greater binding affinity to PD-L1. In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to PD-L1 have an increase in binding affinity relative to the wild-type or unmodified CD80 polypeptide control of at least about 5%, such as at least about 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more for PD-L1. In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to PD-L1 have an equilibrium dissociation constant (Kd) of less than 200 pM, 300 pM, 400 pM, 500 pM, or 600 pM for PD-L1. In some embodiments, the variant polypeptide specifically binds to the ectodomain of one of PD-L1 with increased selectivity compared to the unmodified CD80. In some embodiments, the increased selectivity is for PD-L1 . 
     In some embodiments, variant CD80 polypeptides have an increased or greater binding affinity to CTLA-4. In some embodiments, variant CD80 polypeptides with increased or greater binding affinity to CTLA-4 have an increase in binding affinity relative to the wild-type or unmodified CD80 polypeptide control of at least about 5%, such as at least about 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or more for CTLA-4. In some embodiments, variant CD80 polypeptide with increased or greater binding affinity to CTLA-4 have an equilibrium dissociation constant (Kd) of less than 200 pM, 300 pM, 400 pM, 500 pM, or 600 pM for CTLA-4. In some embodiments, the variant polypeptide specifically binds to the ectodomain of one of CTLA-4 with increased selectivity compared to the unmodified CD80. In some embodiments, the increased selectivity is for CTLA-4. 
     In some embodiments, the increased selectivity comprises a greater ratio of binding of the variant CD80 polypeptide for one cognate binding partner selected from among PD-L1, CD28 and CTLA4 versus another of the cognate binding partner compared to the ratio of binding of the unmodified CD80 polypeptide for the one cognate binding partner versus the another of the cognate binding partner. In some embodiments, the ratio is greater by at least or at least about 1.5-fold, 2-fold, 3-fold, 4-fold, 5-fold, 10-fold, 15-fold, 20-fold, 30-fold, 40-fold, 50-fold or more. 
     The wild-type or unmodified CD80 sequence does not necessarily have to be used as a starting composition to generate variant CD80 polypeptides described herein. Therefore, use of the term “modification”, such as “substitution” does not imply that the present embodiments are limited to a particular method of making variant CD80 polypeptides. Variant CD80 polypeptides can be made, for example, by de novo peptide synthesis and thus does not necessarily require a modification, such as a “substitution”, in the sense of altering a codon to encode for the modification, e.g. substitution. This principle also extends to the terms “addition” and “deletion” of an amino acid residue which likewise do not imply a particular method of making. The means by which the variant CD80 polypeptides are designed or created is not limited to any particular method. In some embodiments, however, a wild-type or unmodified CD80 encoding nucleic acid is mutagenized from wild-type or unmodified CD80 genetic material and screened for desired specific binding affinity and/or induction of IL-2 expression or other functional activity. In some embodiments, variant CD80 polypeptides are synthesized de novo utilizing protein or nucleic acid sequences available at any number of publicly available databases and then subsequently screened. The National Center for Biotechnology Information provides such information and its website is publicly accessible via the interne as is the UniProtKB database as discussed previously. 
     Unless stated otherwise, as indicated throughout the present disclosure, the amino acid substitution(s) are designated by amino acid position number corresponding to the numbering of positions of the unmodified ECD sequence set forth in SEQ ID NO: 1. 
     It is within the level of a skilled artisan to identify the corresponding position of a modification, e.g. amino acid substitution, in an CD80 polypeptide, including portion thereof containing an IgSF domain (e.g. IgC or IgV) thereof, such as by alignment of a reference sequence with SEQ ID NO: 1. In the listing of modifications throughout this disclosure, the amino acid position is indicated in the middle, with the corresponding unmodified (e.g. wild-type) amino acid listed before the number and the identified variant amino acid substitution listed after the number. If the modification is a deletion of the position a “del” is indicated and if the modification is an insertion at the position an “ins” is indicated. 
     In some embodiments, the variant CD80 polypeptide has one or more amino acid modification, e.g. substitution in a wild-type or unmodified CD80 sequence. The one or more amino acid modification, e.g. substitution can be in the ectodomain (extracellular domain) of the wild-type or unmodified CD80 sequence. In some embodiments, the one or more amino acid modification, e.g. substitution is in the IgC domain or specific binding fragment thereof. In some embodiments, the one or more amino acid modification, e.g. substitution is in the IgV domain or specific binding fragment thereof. In some embodiments of the variant CD80 polypeptide, some of the one or more amino acid modification, e.g. substitution is in the IgC domain or a specific binding fragment thereof, and some of the one or more amino acid modification, e.g. substitution are in the IgV domain or a specific binding fragment thereof. 
     In some embodiments, the variant CD80 polypeptide has up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acid modification(s), e.g. substitution. The modification, e.g. substitution can be in the IgC domain or the IgV domain. In some embodiments, the variant CD80 polypeptide has up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acid substitutions in the IgC domain or specific binding fragment thereof. In some embodiments, the variant CD80 polypeptide has up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acid substitutions in the IgV domain or specific binding fragment thereof. In some embodiments, the variant CD80 polypeptide has at least about 80%, 81%, 82%, 83%, 84%, 85%, 86%, 86%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% sequence identity with the wild-type or unmodified CD80 polypeptide or specific binding fragment thereof, such as with the amino acid sequence of SEQ ID NO: 1. 
     In some embodiments, the variant CD80 polypeptide has one or more amino acid modification, e.g. substitution in an unmodified CD80 or specific binding fragment there of corresponding to position(s) 130, 131, 139, 155, 156, 165 or 166 with reference to numbering of SEQ ID NO: 1. In some embodiments, such variant CD80 polypeptides exhibit altered binding affinity to one or more of CD28, PD-L1, and/or CTLA-4 compared to the wild-type or unmodified CD80 polypeptide. For example, in some embodiments, the variant CD80 polypeptide exhibits increased binding affinity to CD28, PD-L1, and/or CTLA-4 compared to a wild-type or unmodified CD80 polypeptide. In some embodiments, the variant CD80 polypeptide exhibits decreased binding affinity to CD28, PD-L1, or CTLA-4 compared to a wild-type or unmodified CD80 polypeptide. 
     In some embodiments, the variant CD80 polypeptide has one or more amino acid modification, e.g. substitution selected from T130A, S131A, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, L139V, V155A, V155I, or V155T, A165S, A165V, A165I, A165F, A165R, A165E, A165D, or A165Q. V166A, V166L or V166T or a conservative amino acid modification, e.g. substitution thereof. A conservative amino acid modification, e.g. substitution is any amino acid that falls in the same class of amino acids as the substituted amino acids, other than the wild-type or unmodified amino acid. The classes of amino acids are aliphatic (glycine, alanine, valine, leucine, and isoleucine), hydroxyl or sulfur-containing (serine, cysteine, threonine, and methionine), cyclic (proline), aromatic (phenylalanine, tyrosine, tryptophan), basic (histidine, lysine, and arginine), and acidic/amide (aspartate, glutamate, asparagine, and glutamine). 
     In some embodiments, the variant CD80 polypeptide has one or more amino acid modification, e.g. substitution selected from T130A, S131A, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, L139V, V155A, V155I, or V155T, A165S, A165V, A165I, A165F, A165R, A165E, A165D, or A165Q. V166A, V166L or V166T. 
     In some embodiments, the one or more amino acid modification, e.g. substitution is T130A, S131A, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, L139V, V155A, V155I, or V155T, A165S, A165V, A165I, A165F, A165R, A165E, A165D, or A165Q. V166A, V166L, V166T, 
     In some embodiments, the variant CD80 polypeptide comprises any of the mutations listed in Table 1. As indicated, the exact locus or residues corresponding to a given domain can vary, such as depending on the methods used to identify or classify the domain. Also, in some cases, adjacent N- and/or C-terminal amino acids of a given domain (e.g. IgV) also can be included in a sequence of a variant IgSF polypeptide, such as to ensure proper folding of the domain when expressed. 
     In some embodiments, the variant CD80 polypeptide comprises any of the mutations listed in Table 1, relative to the human CD80 protein, or at the corresponding position in the non-human protein version. In some embodiments, the variant CD80 polypeptide comprises mutations of the extracellular domain (ECD) or IgV sequences as provided for in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Exemplary variant CD80 polypeptides 
               
            
           
           
               
               
               
               
            
               
                 Position 
                 Single Mutation 
                 Double Mutations 
                 Triple Mutations 
               
               
                   
               
               
                 T130 
                 T130A 
                 T130A/S156A 
                   
               
               
                 S131 
                 S131A, S131V, 
                 S131A/S156I 
                 S131A/S156I/A165S 
               
               
                   
                 S131I, S131F, 
                 S131A/A165S 
                   
               
               
                   
                 S131R, S131E, 
                   
                   
               
               
                   
                 S131D, S131Q 
                   
                   
               
               
                 L139 
                   
                 L139V/V166L 
                 L139V/S156A/V166L 
               
               
                 V155 
                 V155A, V155I, 
                 V155A/S156A 
                   
               
               
                   
                 V155T 
                 V155I/S156A 
                   
               
               
                   
                   
                 V155T/S156A 
                   
               
               
                 S156 
                 S156V, S156L, 
                 S156A/V155A 
                 S156A/V166L/L139V 
               
               
                   
                 S156I, S156F, 
                 S156A/V155I 
                 S156I/A165S/S131A 
               
               
                   
                 S156R, S156E, 
                 S156A/V155T 
                   
               
               
                   
                 S156D, S156Q 
                 S156A/T130A 
                   
               
               
                   
                   
                 S156A/V166A 
                   
               
               
                   
                   
                 S156I/A165S 
                   
               
               
                   
                   
                 S156I/S131A 
                   
               
               
                 A165 
                 A165S, A165V, 
                 A165S/S156I 
                 A165S/S131A/S156I 
               
               
                   
                 A165I, A165F, 
                 A165S/S131A 
                   
               
               
                   
                 A165R, A165E, 
                   
                   
               
               
                   
                 A165D, A165Q 
                   
                   
               
               
                 V166 
                 V166A, V166T 
                 V166L/L139V 
                 V166L/L139V/S156A 
               
               
                   
                   
                 V166A/S156A 
               
               
                   
               
            
           
         
       
     
     To provide a surrogate model for in vivo studies, the following mouse CD80 variant polypeptides can be made and tested based on wild type mouse CD80 sequence, T165E, T165Q, T165R, T165A, T165S, T165V, T165I, T165F, T165D, S131V, S131I, S131F, S131R, S131E, S131Q, S131A, and S131P. The wild type mouse sequence is provided in  FIG. 14B , and is provided as SEQ ID NO: 15. 
     III. Pharmaceutical Compositions 
     The present disclosure provides a pharmaceutical composition comprises the variant CD80 polypeptide of the present disclosure. In some embodiments, the pharmaceutical composition further comprises a pharmaceutically acceptable excipient. In some embodiments, the pharmaceutical composition is sterile. In some embodiments, a kit comprises the pharmaceutical composition of the present disclosure, and instructions for use. 
     In other embodiments, an article of manufacture comprises the pharmaceutical composition of the present disclosure in a vial. In some embodiments, the vial is sealed. In some embodiments, a kit comprises the article of manufacture of the present disclosure, and instructions for use. 
     The pharmaceutical composition of the present disclosure can comprise, in addition to a multimeric polypeptide of the present disclosure, one or more of: a salt, e.g., NaCl, MgC12, KC1, MgSO4, etc.; a buffering agent, e.g., a Tris buffer, N-(2-Hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES), 2-(N-Morpholino) ethanesulfonic acid (MES), 2-(N-Morpholino) ethanesulfonic acid sodium salt (MES), 3-(N-Morpholino) propanesulfonic acid (MOPS), N-tris [Hydroxymethyl]methyl-3-aminopropanesulfonic acid (TAPS), etc.; a solubilizing agent; a detergent, e.g., a non-ionic detergent such as Tween-20, etc.; a protease inhibitor; glycerol; and the like. 
     The pharmaceutical composition may comprise a pharmaceutically acceptable excipient, a variety of which are known in the art and need not be discussed in detail herein. Pharmaceutically acceptable excipients have been amply described in a variety of publications, including, for example, “Remington: The Science and Practice of Pharmacy”, 19th Ed. (1995), or latest edition, Mack Publishing Co; A. Gennaro (2000) “Remington: The Science and Practice of Pharmacy”, 20th edition, Lippincott, Williams, &amp; Wilkins; Pharmaceutical Dosage Forms and Drug Delivery Systems (1999) H. C. Ansel et al., eds 7th ed., Lippincott, Williams, &amp; Wilkins; and Handbook of Pharmaceutical Excipients (2000) A. H. Kibbe et al., eds., 3rd ed. Amer. Pharmaceutical Assoc. 
     A pharmaceutical composition can comprise a multimeric polypeptide of the present disclosure, and a pharmaceutically acceptable excipient. In some cases, a subject pharmaceutical composition is suitable for administration to a subject, e.g., is sterile. For example, in some embodiments, a subject pharmaceutical composition is suitable for administration to a human subject, e.g., where the composition is sterile and is free of detectable pyrogens and/or other toxins. 
     The protein compositions may comprise other components, such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharin, talcum, cellulose, glucose, sucrose, magnesium, carbonate, and the like. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions such as pH adjusting and buffering agents, toxicity adjusting agents and the like, for example, sodium acetate, sodium chloride, potassium chloride, calcium chloride, sodium lactate, hydrochloride, sulfate salts, solvates (e.g., mixed ionic salts, water, organics), hydrates (e.g., water), and the like. 
     For example, compositions may include aqueous solution, powder form, granules, tablets, pills, suppositories, capsules, suspensions, sprays, and the like. The composition may be formulated according to the various routes of administration described below. 
     Where a polypeptide or a multimeric or dimeric protein of the present disclosure is administered as an injectable (e.g. subcutaneously, intraperitoneally, intramuscularly, and/or intravenously) directly into a tissue, a formulation can be provided as a ready-to-use dosage form, or as non-aqueous form (e.g. a reconstitutable storage-stable powder) or aqueous form, such as liquid composed of pharmaceutically acceptable carriers and excipients. The protein-containing formulations may also be provided so as to enhance serum half-life of the subject protein following administration. For example, the protein may be provided in a liposome formulation, prepared as a colloid, or other conventional techniques for extending serum half-life. A variety of methods are available for preparing liposomes, as described in, e.g., Szoka et al. 1980 Ann. Rev. Biophys. Bioeng. 9:467, U.S. Pat. Nos. 4,235,871, 4,501,728 and 4,837,028. The preparations may also be provided in controlled release or slow-release forms. 
     Other examples of formulations suitable for parenteral administration include isotonic sterile injection solutions, anti-oxidants, bacteriostats, and solutes that render the formulation isotonic with the blood of the intended recipient, suspending agents, solubilizers, thickening agents, stabilizers, and preservatives. For example, a subject pharmaceutical composition can be present in a container, e.g., a sterile container, such as a syringe. The formulations can be presented in unit-dose or multi-dose sealed containers, such as ampules and vials, and can be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid excipient, for example, water, for injections, immediately prior to use. Extemporaneous injection solutions and suspensions can be prepared from sterile powders, granules, and tablets. 
     The concentration of a polypeptide or a multimeric or dimeric protein of the present disclosure in a formulation can vary widely (e.g., from less than about 0.1%, usually at or at least about 2% to as much as 20% to 50% or more by weight) and will usually be selected primarily based on fluid volumes, viscosities, and patient-based factors in accordance with the particular mode of administration selected and the patient&#39;s needs. 
     The present disclosure provides a container comprising a composition of the present disclosure, e.g., a liquid composition. The container can be, e.g., a syringe, an ampoule, and the like. In some cases, the container is sterile. In some cases, both the container and the composition are sterile. 
     IV. Methods of Use 
     In some embodiments, provided herein is a method of modulating an immune response in a subject, comprising administering the pharmaceutical composition of the present disclosure to the subject. In some embodiments, modulating the immune response treats a disease or condition in the subject. In some embodiments, the immune response is increased. In some embodiments, the immune response is decreased. 
     In some embodiments, the disease or condition is a tumor or cancer. In some embodiments, the disease or condition is selected from melanoma, lung cancer, bladder cancer, a hematological malignancy, liver cancer, brain cancer, renal cancer, breast cancer, pancreatic cancer, colorectal cancer, spleen cancer, prostate cancer, testicular cancer, ovarian cancer, uterine cancer, gastric carcinoma, a musculoskeletal cancer, a head and neck cancer, a gastrointestinal cancer, a germ cell cancer, or an endocrine and neuroendocrine cancer. In some embodiments, the disease or condition is an inflammatory or autoimmune disease or condition. In some embodiments, the disease or condition is an antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, a vasculitis, an autoimmune skin disease, transplantation, a Rheumatic disease, an inflammatory gastrointestinal disease, an inflammatory eye disease, an inflammatory neurological disease, an inflammatory pulmonary disease, an inflammatory endocrine disease, or an autoimmune hematological disease. In some embodiments, the disease or condition is selected from inflammatory bowel disease, transplant, Crohn&#39;s disease, ulcerative colitis, multiple sclerosis, asthma, rheumatoid arthritis, or psoriasis. 
     In some embodiments, provided herein is a method of treating a disease or condition in a subject, comprising administering the pharmaceutical composition of the present disclosure to the subject. 
     In some embodiments, the disease or condition is a tumor or cancer. In some embodiments, provided herein is a the disease or condition is selected from melanoma, lung cancer, bladder cancer, a hematological malignancy, liver cancer, brain cancer, renal cancer, breast cancer, pancreatic cancer, colorectal cancer, spleen cancer, prostate cancer, testicular cancer, ovarian cancer, uterine cancer, gastric carcinoma, a musculoskeletal cancer, a head and neck cancer, a gastrointestinal cancer, a germ cell cancer, or an endocrine and neuroendocrine cancer. 
     In some embodiments, the disease or condition is an infection. In some embodiments, the disease or condition is an inflammatory or autoimmune disease or condition. In some embodiments, provided herein is a the disease or condition is an antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, a vasculitis, an autoimmune skin disease, transplantation, a Rheumatic disease, an inflammatory gastrointestinal disease, an inflammatory eye disease, an inflammatory neurological disease, an inflammatory pulmonary disease, an inflammatory endocrine disease, or an autoimmune hematological disease. In some embodiments, provided herein is a the disease or condition is selected from inflammatory bowel disease, transplant, Crohn&#39;s disease, ulcerative colitis, multiple sclerosis, asthma, rheumatoid arthritis, or psoriasis. 
     In some embodiments, the patient is administered with a second therapeutic agent. 
     EXAMPLES 
     The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present disclosure, and are not intended to limit the scope of what the inventors regard as their disclosure nor are they intended to represent that the experiments below are all or the only experiments performed. 
     Example 1 
     Construction of Expression Vectors for Production of Mutant CD8O-Fc Fusion Proteins and Expression/Purification of Mutant CD8O-Fc Fusion Proteins (CD80 Variants) 
     Wild-type human CD80-human IgG1 Fc expression cassette (hCD8O-Fc, FIG.13Awas generated by de novo gene synthesis and was cloned into pcDNA3.4 vector (Thermo Fisher Scientific). Mutations to the CD80 IgC domain at positions S131, V155, A165 and V166 were introduced by either site-directed mutagenesis employing QuikChange Lightening Site-Directed Mutagenesis Kit (Agilent) or by direct DNA synthesis (GenScript) according to the Provider&#39;s manual/protocol. The primers for site-directed mutagenesis were listed in Tables 2 and 3, and used for single site-directed mutagenesis. QuikChange Lightening Multi Site-Directed Mutagenesis Kit was used for multiple site-directed mutagenesis. 
     The constructed pcDNA3.4 expression vectors containing polynucleotides encoding either wild-type CD80 or mutated CD80 variants described in Table 1 and  FIGS. 13A  and 24 were transfected into Expi293F cells using ExpiFectamine 293 transfection reagent (Thermo Fisher Scientific). ExpiFectamine 293 Transfection Enhancer 1 and Enhancer 2 were added to the well 20 hours after transfection. The cultures were incubated at 37° C. in humidified incubator at 75% humidity supplied with 5% CO 2 . The transfected culture was harvested 6 days post transfection. The CD80-Fc Fusion Proteins expressed from the transfected Expi293F cells were purified using GE Healthcare Protein A HP SpinTrap column by incubating the supernatants and the resin at room temperature for 4 minutes. The column was washed with sodium phosphate buffer, pH7.2 and eluted with 100 mM glycine-HC1, pH 3.0. The eluents were neutralized using 1.0 M Tris-HC1, pH 9.0. The purified proteins were dialyzed into PBS buffer at pH7.2 and sterile filtered through 0.2 p.m membrane. The SDS-PAGE analyses were performed and the results of mutant CD80-Fc Fusion Proteins from the analyses were summarized in  FIGS. 15A-15F . All the CD80-Fc Fusion Proteins were purified to near 95% purity. The purified proteins were tested on SDS-PAGE gels in two conditions; (i) a non-reducing condition, which does not break disulfide bonds in a target fusion protein, and (ii) a reducing condition, which breaks disulfide bonds in a target fusion protein. Non-reduced ( FIG. 15A ) and reduced ( FIG. 15B ) samples loaded with each purified variant CD80-Fc Fusion protein are as follows; Lane 1: Molecular Weight Marker; Lane 2: S131F, 1.5 ug/lane; Lane 3: S131R, 1.5 ug/lane; Lane 4: S131E, 2.0 ug/lane; Lane 5: S131D, 1.6 ug/lane; Lane 6: S131Q, 1.6 ug/lane; Lane 7: A165V, 1.2 ug/lane; Lane 8: A165I, 1.6 ug/lane; Lane 9: A165F, 1.6 ug/lane; Lane 10: A165R, 1.6 ug/lane; Lane 11: A165D, 1.6 ug/lane; Lane 12: A165Q, 1.6 ug/lane. Non-reduced ( FIG. 15C ) and reduced ( FIG. 15D ) samples loaded with each purified variant CD80-Fc Fusion protein are as follows; Lane 1: Molecular Weight Marker; Lane 2: V166A, 10/lane; Lane 3: V166T, 10 ug/lane; Lane 4: V166L/L139V, 10 ug/lane; Lane 5: S156A/V155A, 10 ug/lane; Lane 6: S156A/V155I, 10 ug/lane; Lane 7: S156A/V155T, 10 ug/lane; Lane 8: S156A/T130A, 10 ug/lane; Lane 9: S156A/V166A, 10 ug/lane; Lane 10: S156A/V166L/L139V, 10 ug/lane. Non-reduced ( FIG. 15E ) and reduced ( FIG. 15F ) samples loaded with each purified variant CD80-Fc Fusion protein are as follows; Lane 1: Molecular Weight Marker; Lane 2: S131V, 10 ug/lane; Lane 3: V155A, 10 ug/lane; Lane 4: V155I, 10 ug/lane; Lane 5: V155T, 10 ug/lane. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Primers for Site-directed Mutagenesis 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 S156I-f 
                 CCATCAACACAACCGTGATCCAAGACCCCGAAACAG (SEQ ID 
               
               
                   
                 NO: 16) 
               
               
                   
               
               
                 S156I-r 
                 CTGTTTCGGGGTCTTGGATCACGGTTGTGTTGATGG (SEQ ID NO: 
               
               
                   
                 17) 
               
               
                   
               
               
                 A165S-f 
                 CCGAAACAGAGCTCTACAGCGTGAGTAGTAAGCTGG (SEQ ID 
               
               
                   
                 NO: 18) 
               
               
                   
               
               
                 A165S-r 
                 CCAGCTTACTACTCACGCTGTAGAGCTCTGTTTCGG (SEQ ID NO: 
               
               
                   
                 19) 
               
               
                   
               
               
                 S131A-f 
                 ATCATCTGCAGTACCGCTGGTGGGTTCCCTG (SEQ ID NO: 20) 
               
               
                   
               
               
                 S131A-r 
                 CAGGGAACCCACCAGCGGTACTGCAGATGAT (SEQ ID NO: 21) 
               
               
                   
               
               
                 S156F-f 
                 CATCAACACAACCGTGTTCCAAGACCCCGAAACAGAGCTCTAC 
               
               
                   
                 (SEQ ID NO: 22) 
               
               
                   
               
               
                 S156F-r 
                 GTTTCGGGGTCTTGGAACACGGTTGTGTTGATGGCGTTGAG 
               
               
                   
                 (SEQ ID NO: 23) 
               
               
                   
               
               
                 S156R-f 
                 CATCAACACAACCGTGAGGCAAGACCCCGAAACAGAGCTCTAC 
               
               
                   
                 (SEQ ID NO: 24) 
               
               
                   
               
               
                 S156R-r 
                 GTTTCGGGGTCTTGCCTCACGGTTGTGTTGATGGCGTTGAG (SEQ 
               
               
                   
                 ID NO: 25) 
               
               
                   
               
               
                 S156E-f 
                 CATCAACACAACCGTGGAGCAAGACCCCGAAACAGAGCTCTAC 
               
               
                   
                 (SEQ ID NO: 26) 
               
               
                   
               
               
                 S156E-r 
                 GTTTCGGGGTCTTGCTCCACGGTTGTGTTGATGGCGTTGAG (SEQ 
               
               
                   
                 ID NO: 27) 
               
               
                   
               
               
                 S156D-f 
                 CATCAACACAACCGTGGACCAAGACCCCGAAACAGAGCTCTAC 
               
               
                   
                 (SEQ ID NO: 28) 
               
               
                   
               
               
                 S156D-r 
                 GTTTCGGGGTCTTGGTCCACGGTTGTGTTGATGGCGTTGAG (SEQ 
               
               
                   
                 ID NO: 29) 
               
               
                   
               
               
                 S156Q-f 
                 CATCAACACAACCGTGCAGCAAGACCCCGAAACAGAGCTCTAC 
               
               
                   
                 (SEQ ID NO: 30) 
               
               
                   
               
               
                 S156Q-r 
                 GTTTCGGGGTCTTGCTGCACGGTTGTGTTGATGGCGTTGAG (SEQ 
               
               
                   
                 ID NO: 31) 
               
               
                   
               
               
                 S131V-f 
                 CATCTGCAGTACCGTGGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 32) 
               
               
                   
               
               
                 S131V-r 
                 CAGGGAACCCACCCACGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 33) 
               
               
                   
               
               
                 S131I-f 
                 CATCTGCAGTACCATCGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 34) 
               
               
                   
               
               
                 S131I-r 
                 CAGGGAACCCACCGATGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 35) 
               
               
                   
               
               
                 S131F-f 
                 CATCTGCAGTACCTTCGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 36) 
               
               
                   
               
               
                 S131F-r 
                 CAGGGAACCCACCGAAGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 37) 
               
               
                   
               
               
                 S131R-f 
                 CATCTGCAGTACCAGGGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 38) 
               
               
                   
               
               
                 S131R-r 
                 CAGGGAACCCACCCCTGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 39) 
               
               
                   
               
               
                 S131E-f 
                 CATCTGCAGTACCGAGGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 40) 
               
               
                   
               
               
                 S131E-r 
                 CAGGGAACCCACCCTCGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 41) 
               
               
                   
               
               
                 S131D-f 
                 CATCTGCAGTACCGACGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 42) 
               
               
                   
               
               
                 S131D-r 
                 CAGGGAACCCACCGTCGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 43) 
               
               
                   
               
               
                 S131Q-f 
                 CATCTGCAGTACCCAGGGTGGGTTCCCTGAGCCCCATCTC (SEQ 
               
               
                   
                 ID NO: 44) 
               
               
                   
               
               
                 S131Q-r 
                 CAGGGAACCCACCCTGGGTACTGCAGATGATTCTCCTG (SEQ ID 
               
               
                   
                 NO: 45) 
               
               
                   
               
               
                 A165V-f 
                 GAAACAGAGCTCTACGTGGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 46) 
               
               
                   
               
               
                 A165V-r 
                 CTTACTACTCACCACGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 47) 
               
               
                   
               
               
                 A165I-f 
                 GAAACAGAGCTCTACATCGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 48) 
               
               
                   
               
               
                 A165I-r 
                 CTTACTACTCACGATGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 49) 
               
               
                   
               
               
                 A165F-f 
                 GAAACAGAGCTCTACTTCGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 50) 
               
               
                   
               
               
                 A165F-r 
                 CTTACTACTCACGAAGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 51) 
               
               
                   
               
               
                 A165R-f 
                 GAAACAGAGCTCTACAGGGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 52) 
               
               
                   
               
               
                 A165R-r 
                 CTTACTACTCACCCTGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 53) 
               
               
                   
               
               
                 A165E-f 
                 GAAACAGAGCTCTACGAGGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 54) 
               
               
                   
               
               
                 A165E-r 
                 CTTACTACTCACCTCGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 55) 
               
               
                   
               
               
                 A165D-f 
                 GAAACAGAGCTCTACGACGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 56) 
               
               
                   
               
               
                 A165D-r 
                 CTTACTACTCACGTCGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 57) 
               
               
                   
               
               
                 A165Q-f 
                 GAAACAGAGCTCTACCAGGTGAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 58) 
               
               
                   
               
               
                 A165Q-r 
                 CTTACTACTCACCTGGTAGAGCTCTGTTTCGGGGTCTTG (SEQ ID 
               
               
                   
                 NO: 59) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Primers for Site-directed Mutagenesis 
               
            
           
           
               
               
            
               
                 Primer ID 
                 primer sequence 
               
               
                   
               
               
                 T130A-f 
                 CAGGAGAATCATCTGCAGTGCATCTGGTGGGTTCCCTGAG (SEQ 
               
               
                   
                 ID NO: 60) 
               
               
                   
               
               
                 T130A-r 
                 CTCAGGGAACCCACCAGATGCACTGCAGATGATTCTCCTG (SEQ 
               
               
                   
                 ID NO: 61) 
               
               
                   
               
               
                 S131V-f 
                 GAGAATCATCTGCAGTACCGTTGGTGGGTTCCCTGAGCC (SEQ ID 
               
               
                   
                 NO: 62) 
               
               
                   
               
               
                 S131V-r 
                 GGCTCAGGGAACCCACCAACGGTACTGCAGATGATTCTC (SEQ ID 
               
               
                   
                 NO: 63) 
               
               
                   
               
               
                 L139V-f 
                 GTTCCCTGAGCCCCATGTTAGCTGGCTGGAGAACG (SEQ ID NO: 
               
               
                   
                 64) 
               
               
                   
               
               
                 L139V-r 
                 CGTTCTCCAGCCAGCTAACATGGGGCTCAGGGAAC (SEQ ID NO: 
               
               
                   
                 65) 
               
               
                   
               
               
                 V155A-f 
                 CAACGCCATCAACACAACCGCATCCCAAGACCCCGAAACAG 
               
               
                   
                 (SEQ ID NO: 66) 
               
               
                   
               
               
                 V155A-r 
                 CTGTTTCGGGGTCTTGGGATGCGGTTGTGTTGATGGCGTTG (SEQ 
               
               
                   
                 ID NO: 67) 
               
               
                   
               
               
                 V155I-f 
                 CAACGCCATCAACACAACCATCTCCCAAGACCCCGAAACAG 
               
               
                   
                 (SEQ ID NO: 68) 
               
               
                   
               
               
                 V155I-r 
                 CTGTTTCGGGGTCTTGGGAGATGGTTGTGTTGATGGCGTTG (SEQ 
               
               
                   
                 ID NO: 69) 
               
               
                   
               
               
                 V155T-f 
                 CAACGCCATCAACACAACCACCTCCCAAGACCCCGAAACAG 
               
               
                   
                 (SEQ ID NO: 70) 
               
               
                   
               
               
                 V155T-r 
                 CTGTTTCGGGGTCTTGGGAGGTGGTTGTGTTGATGGCGTTG (SEQ 
               
               
                   
                 ID NO: 71) 
               
               
                   
               
               
                 S156A-f 
                 GCCATCAACACAACCGTGGCACAAGACCCCGAAACAGAG (SEQ 
               
               
                   
                 ID NO: 72) 
               
               
                   
               
               
                 S156A-r 
                 CTCTGTTTCGGGGTCTTGTGCCACGGTTGTGTTGATGGC (SEQ ID 
               
               
                   
                 NO: 73) 
               
               
                   
               
               
                 V166A-f 
                 CGAAACAGAGCTCTACGCCGCAAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 74) 
               
               
                   
               
               
                 V166A-r 
                 GTTAAAGTCCAGCTTACTACTTGCGGCGTAGAGCTCTGTTTCG 
               
               
                   
                 (SEQ ID NO: 75) 
               
               
                   
               
               
                 V166L-f 
                 CCGAAACAGAGCTCTACGCCCTCAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 76) 
               
               
                   
               
               
                 V166L-r 
                 GTTAAAGTCCAGCTTACTACTGAGGGCGTAGAGCTCTGTTTCGG 
               
               
                   
                 (SEQ ID NO: 77) 
               
               
                   
               
               
                 V166T-f 
                 CCGAAACAGAGCTCTACGCCACCAGTAGTAAGCTGGACTTTAAC 
               
               
                   
                 (SEQ ID NO: 78) 
               
               
                   
               
               
                 V166T-r 
                 GTTAAAGTCCAGCTTACTACTGGTGGCGTAGAGCTCTGTTTCGG 
               
               
                   
                 (SEQ ID NO: 79) 
               
               
                   
               
               
                 S155A/S156A- 
                 CAACGCCATCAACACAACCGCAGCACAAGACCCCGAAACAGAGC 
               
               
                 f 
                 (SEQ ID NO: 80) 
               
               
                   
               
               
                 S155A/S156A- 
                 GCTCTGTTTCGGGGTCTTGTGCTGCGGTTGTGTTGATGGCGTTG 
               
               
                 r 
                 (SEQ ID NO: 81) 
               
               
                   
               
               
                 V155I/S156A- 
                 CAACGCCATCAACACAACCATCGCCCAAGACCCCGAAACAGAGC 
               
               
                 f 
                 (SEQ ID NO: 82) 
               
               
                   
               
               
                 V155I/S156A- 
                 GCTCTGTTTCGGGGTCTTGGGCGATGGTTGTGTTGATGGCGTTG 
               
               
                 r 
                 (SEQ ID NO: 83) 
               
               
                   
               
               
                 V155T/5156A- 
                 CAACGCCATCAACACAACCACCGCCCAAGACCCCGAAACAGAG 
               
               
                 f 
                 (SEQ ID NO: 84) 
               
               
                   
               
               
                 V155T/S156A- 
                 CTCTGTTTCGGGGTCTTGGGCGGTGGTTGTGTTGATGGCGTTG 
               
               
                 r 
                 (SEQ ID NO: 85) 
               
               
                   
               
            
           
         
       
     
     Example 2 
     Assessment of Binding Affinities of CD80 Variants to CTLA-4, PD-L1 and CD28 by ELISA and Biacore 
     (1) CD80 Mutant Binding Affinity by ELISA: 
     For testing binding affinity by ELISA, at first ELISA plates were coated with 1 ug/mL hCTLA-4 (recombinant His Tag from Sino Biological) at 4° C. overnight. The next day, the hCTLA-4 solution was removed and the plates were blocked with 1% BSA at room temperature for 1 hour. After removing the 1% BSA solution, the plates were washed with PBST (phosphate buffered saline with 0.05% of Tween-20) three times. The samples of the purified CD80 variants for this binding assay were added at 100 uL/well in duplicate with 1:3 serial dilutions starting at the concentration of 4 ug/mL and incubated at room temperature for 2 hours with agitation. After washing with PBST three times, a secondary antibody, 100 uL/well of 1:10,000 dilution of HRP-anti-hIgG, was added and incubated at room temperature for 1 hour with agitation. The plates were wash three times with PBST, and a 100 uL/well of TMB substrate was added. The plates were incubated until the color was developed. The stop-solution was added to stop the reaction. The plates were read at OD450. 
     The similar ELISA experiments were performed for CD28 and PD-L1 recombinant proteins, respectively except the plates were coated with 2 ug/mL of recombinant CD28 and PD-L1 proteins (recombinant His Tag from Sino Biological) and the dilutions of CD80 variants were started at 20 ug/mL. 
     The EC 50  values of CD80 variants binding to CTLA-4, CD28 or PD-L1 were determined by comparing to EC 50  of wild-type CD80 on each plate. 
     The results of binding affinity assays by ELISA were presented in  FIGS. 16A-16F  (binding affinity of CD80 variants to CTLA-4). Table 4 summarizes results of binding assays presented in  FIGS. 16A -16E with top OD450 values of each tested CD80-Fc Fusion protein including single, double and triple mutations (e.g. S156I/A165S, S156I/S131A, A165S/S131A, S156I/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with EC 50  (ug/ml) values. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. Table 5 summarizes results of binding assays presented in  FIG. 16F  with top OD450 values of each tested CD80-Fc Fusion protein (e.g. T130A, S131V, L139V, V155A, V155I, V155T, S156A, V166A, V166L, V166T, V155A/S156A, V155I/S156A, V155T/S156A, and CD80-WT), along with ECso (ug/ml) values. The ECso (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results of binding affinity assays by ELISA were presented in  FIGS. 17A-17E  (binding affinity of CD80 variants to CD28). Table 6 summarizes results of binding assays presented in  FIGS. 17A-17E  with top OD450 values of each tested CD80-Fc Fusion protein including single, double and triple mutations (e.g. S156I/A165S, S156I/S131A, A165S/S131A, S156I/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with ECso (ug/ml) values. The ECso (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results of binding affinity assays by ELISA were presented in  FIGS. 18A-18E  (binding affinity of CD80 variants to PD-L1). Table 7 summarizes results of binding assays presented in  FIGS. 18A-18E  with top OD450 values of each tested CD80-Fc Fusion Protein including single, double and triple mutations (e.g. S156I/A165S, S156I/S131A, A165S/S131A, S156I/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 CTLA4-CD80 
                 Top OD 
                 EC50(ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 CD80-WT 
                 1.50 
                 0.0110 
               
               
                   
                 S156I/A165S 
                 1.41 
                 0.0120 
               
               
                   
                 S156I/S131A 
                 1.59 
                 0.0100 
               
               
                   
                 A165S/S131A 
                 1.47 
                 0.0120 
               
               
                   
                 S156I/A165S/S131A 
                 1.50 
                 0.0130 
               
               
                   
                 S156F 
                 1.58 
                 0.0090 
               
               
                   
                 S156R 
                 1.57 
                 0.0140 
               
               
                   
                 S156E 
                 1.34 
                 0.0110 
               
               
                   
                 S156D 
                 1.55 
                 0.0150 
               
               
                   
                 S156Q 
                 1.68 
                 0.0120 
               
               
                   
                 S131V 
                 1.48 
                 0.0200 
               
               
                   
                 S131I 
                 1.60 
                 0.0150 
               
               
                   
                 S131F 
                 1.68 
                 0.0141 
               
               
                   
                 S131R 
                 1.60 
                 0.0058 
               
               
                   
                 S131E 
                 1.50 
                 0.0130 
               
               
                   
                 S131D 
                 1.30 
                 0.0260 
               
               
                   
                 S131Q 
                 1.46 
                 0.0130 
               
               
                   
                 A165V 
                 1.44 
                 0.0370 
               
               
                   
                 A165I 
                 1.32 
                 0.0890 
               
               
                   
                 A165F 
                 0.90 
                 0.0310 
               
               
                   
                 A165R 
                 1.01 
                 0.0210 
               
               
                   
                 A165E 
                 1.04 
                 0.0090 
               
               
                   
                 A165D 
                 0.87 
                 0.0180 
               
               
                   
                 A165Q 
                 0.82 
                 0.0120 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 CD80-WT 
                 1.11 
                 0.04846 
               
               
                   
                 T130A 
                 1.198 
                 0.01983 
               
               
                   
                 S131V 
                 1.053 
                 0.0321 
               
               
                   
                 L139V 
                 1.314 
                 0.0268 
               
               
                   
                 V155A 
                 1.095 
                 0.02888 
               
               
                   
                 V155I 
                 0.9623 
                 0.08108 
               
               
                   
                 V155T 
                 0.8803 
                 0.06053 
               
               
                   
                 S156A 
                 1.159 
                 0.04707 
               
               
                   
                 V166A 
                 0.9512 
                 0.06625 
               
               
                   
                 V166L 
                 1.162 
                 0.02897 
               
               
                   
                 V166T 
                 0.9639 
                 0.01365 
               
               
                   
                 V155A/S156A 
                 1.151 
                 0.02742 
               
               
                   
                 V155I/S156A 
                 1.095 
                 0.1835 
               
               
                   
                 V155T/S156A 
                 0.8386 
                 0.05937 
               
               
                   
                   
               
            
           
         
       
     
     S131E, S131D, S131Q, A165V, A1651, A165F, A165R, A165E, A165D, and A165Q), along with EC50 (ug/ml) values. The EC50 (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 CD28-CD80 
                 Top OD 
                 EC50(ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 CD80-WT 
                 2.51 
                 2.42 
               
               
                   
                 S156I/A165S 
                 2.22 
                 2.42 
               
               
                   
                 S156I/S131A 
                 2.20 
                 4.36 
               
               
                   
                 A165S/S131A 
                 2.33 
                 5.02 
               
               
                   
                 S156I/A165S/S131A 
                 2.26 
                 4.85 
               
               
                   
                 S156F 
                 2.19 
                 2.20 
               
               
                   
                 S156R 
                 1.83 
                 7.66 
               
               
                   
                 S156E 
                 2.12 
                 4.18 
               
               
                   
                 S156D 
                 2.12 
                 4.29 
               
               
                   
                 S156Q 
                 2.14 
                 4.05 
               
               
                   
                 S131V 
                 1.27 
                 32.46 
               
               
                   
                 S131I 
                 1.76 
                 10.75 
               
               
                   
                 S131F 
                 1.22 
                 . . . 
               
               
                   
                 S131R 
                 1.75 
                 23.26 
               
               
                   
                 S131E 
                 1.72 
                 . . . 
               
               
                   
                 S131D 
                 1.31 
                 . . . 
               
               
                   
                 S131Q 
                 1.63 
                 13.60 
               
               
                   
                 A165V 
                 1.02 
                 135.30 
               
               
                   
                 A165I 
                 0.67 
                 2.10 
               
               
                   
                 A165F 
                 0.74 
                 14.86 
               
               
                   
                 A165R 
                 1.10 
                 . . .  
               
               
                   
                 A165E 
                 1.78 
                 34.07 
               
               
                   
                 A165D 
                 1.36 
                 . . .  
               
               
                   
                 A165Q 
                 1.76 
                 157.10 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 PD-L1-CD80 
                 Top OD 
                 EC50(ug/ml) 
               
               
                   
                   
               
             
            
               
                   
                 CD80-WT 
                 1.07 
                 0.98 
               
               
                   
                 S156I/A165S 
                 0.70 
                 1.17 
               
               
                   
                 S156I/S131A 
                 0.74 
                 0.52 
               
               
                   
                 A165S/S131A 
                 0.83 
                 1.23 
               
               
                   
                 S156I/A165S/S131A 
                 0.71 
                 1.96 
               
               
                   
                 S156F 
                 0.94 
                 0.37 
               
               
                   
                 S156R 
                 0.91 
                 0.49 
               
               
                   
                 S156E 
                 0.72 
                 0.67 
               
               
                   
                 S156D 
                 0.83 
                 0.57 
               
               
                   
                 S156Q 
                 0.92 
                 0.55 
               
               
                   
                 S131V 
                 0.94 
                 0.40 
               
               
                   
                 S131I 
                 0.87 
                 0.24 
               
               
                   
                 S131F 
                 0.96 
                 0.21 
               
               
                   
                 S131R 
                 0.79 
                 0.58 
               
               
                   
                 S131E 
                 0.83 
                 0.51 
               
               
                   
                 S131D 
                 0.89 
                 0.28 
               
               
                   
                 S131Q 
                 0.76 
                 0.48 
               
               
                   
                 A165V 
                 0.81 
                 0.14 
               
               
                   
                 A165I 
                 0.81 
                 0.19 
               
               
                   
                 A165F 
                 0.94 
                 0.38 
               
               
                   
                 A165R 
                 0.97 
                 0.26 
               
               
                   
                 A165E 
                 0.80 
                 0.32 
               
               
                   
                 A165D 
                 0.82 
                 0.30 
               
               
                   
                 A165Q 
                 0.92 
                 0.29 
               
               
                   
                   
               
            
           
         
       
     
     (2) CD80 Mutant Binding Affinity Measured by BIAcore: 
     For measuring binding affinity by BlAcore, affinity measurements were carried out on BIAcore model X100 (Biacore/GE Healthcare, Piscataway, NJ) at 25° C. using PBST buffer (20 mM PB+150 mM NaCl +0.05% Tween20, pH 7.4) as a running buffer. NTA sensor chip (catalogue BR-1000-07; GE Healthcare) was chelated with nickel ion (0.5 mM NiC12) in one flow cell at a flow rate of 10 ul/min for 1 minute to capture hCTLA-4 containing a poly-histidine tag at the C-terminus (catalogue 11159-H08H; Sino Biological). The hCTLA-4 solution was injected at a flow rate of 10 ul/min for 2 minutes, then followed by a stabilization time of 3 minutes. hCD80-Fc fusion mutants was then injected in a 2-fold dilution series from sub nM to several hundred nM at a flow rate of 30 ul/min for 3 minutes, and dissociation was monitored for 12 minutes. The regeneration procedure was performed by injecting 350 mM EDTA buffer at a flow rate of 30 ul/min for 3 minutes to remove nickel and any chelated protein. Kinetic analysis was done by simultaneously fitting the association and dissociation phases of the sensorgram using the 1:1 Langmuir binding model in BlAevaluation software (Biacore) as supplied by the manufacturer. Double referencing was applied in each analysis to eliminate background responses from the reference surface and buffer only control.  FIG. 19  depicts results of binding assays of each variant human CD80-IgG1 Fc Fusion protein including single, double and triple mutations (e.g. hCD80(S 156A)-hIgG1, hCD80(S156A)-hIgG1 (FcTm), hCD80(A165S)-hIgG1, hCD80(S 131A)-hIgG1, hCD80(S156V)-hIgG1, hCD80(S 156L)-hIgG1, hCD80(S1560-hIgG1, hCD80(S131V)-hIgG1, hCD80(V155A)-hIgG1, hCD80(V1550-hIgG1, hCD80(V155T)-hIgG1, hCD80(V166A)-hIgG1, hCD80(V166T)-hIgG1, hCD80(V166L/L139V)-hIgG1, hCD80(S156A/V155A)-hIgG1, hCD80(S156A/V155I-hIgG1, hCD80(S 156A/V166T)-hIgG1, hCD80(S156A/T130A)-hIgG1, hCD80(S156A/V166A)-hIgG1, hCD80(S156A/V166L/L139V)-hIgG1) to a binding partner human CTLA-4, compared to a wild-type and unmodified CD80-Fc fusion protein as a control (e.g. hCD80-hLgGl(FcTm, Fc triple mutations for effectorless Fc) and hCD80-hIgG1)), using BlAcore model X100. 
     As shown in  FIG. 19 , all CD80 variants (mutant hCD8O-Fc Fusion Proteins) have higher binding affinity to CTLA-4 than wild-type CD80-Fc fusion protein. 
     (3) CD80 Mutant Binding Affinity Measured by bio-layer interferometry (BLI) biosensor 
     The kinetic affinities of CD80 variants to PD-L1 or CD28 were analyzed by ForteBio&#39;s Octet RED384 system. hPD-L1-His or hCD28-His was immobilized on the surface of the biosensor by capture-based method (sensor type : HIS1K-Anti-Penta-HIS). After the baseline step, biosensors are dipped into a solution containing different concentration of CD80 variants. Experimental temperature was 30° C. and the rotation rate was 1000rpm/min. Running buffer was 20mM PB, 150mM NaCl, 0.05%Tween20, pH7.4, while the regeneration solution was 10mM Glycine-HC1, pH1.5. Table 8 summarizes results of kinetic affinities of CD80 variants to hPD-L1. Table 9 summarizes results of kinetic affinities of CD80 variants to CD28. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Kinetic affinities of CD80 variants to hPD-L1 
               
            
           
           
               
               
               
               
               
            
               
                 Sample ID 
                 Ligand 
                 Kd (M) 
                 Kon(1/Ms) 
                 Kdis(1/s) 
               
               
                   
               
               
                 WT 
                 hPD-L1-His 
                 2.59E−08 
                 5.28E+04 
                 2.68E−03 
               
               
                 S131V 
                 hPD-L1-His 
                 1.75E−07 
                 2.01E+05 
                 3.15E−02 
               
               
                 V155A 
                 hPD-L1-His 
                 3.61E−07 
                 2.23E+05 
                 8.04E−02 
               
               
                 V155I 
                 hPD-L1-His 
                 7.85E−08 
                 3.03E+05 
                 2.38E−02 
               
               
                 V155T 
                 hPD-L1-His 
                 4.96E−08 
                 4.03E+05 
                 2.00E−02 
               
               
                 V166A 
                 hPD-L1-His 
                 6.62E−08 
                 3.69E+06 
                 2.44E−02 
               
               
                 V166T 
                 hPD-L1-His 
                 2.34E−08 
                 3.61E+06 
                 8.45E−03 
               
               
                 V166L/L139V 
                 hPD-L1-His 
                 1.23E−07 
                 2.16E+06 
                 2.65E−02 
               
               
                 S156A/V155A 
                 hPD-L1-His 
                 6.87E−05 
                 1.39E+03 
                 9.57E−02 
               
               
                 S156A/V155I 
                 hPD-L1-His 
                 2.65E−07 
                 1.95E+05 
                 5.18E−02 
               
               
                 S156A/V155T 
                 hPD-L1-His 
                 3.74E−07 
                 2.31E+05 
                 8.66E−02 
               
               
                 S156A/T130A 
                 hPD-L1-His 
                 3.91E−07 
                 1.82E+05 
                 7.12E−02 
               
               
                 S156A/V166A 
                 hPD-L1-His 
                 low 
                 low 
                 low 
               
               
                 S156A/V166L/L139V 
                 hPD-L1-His 
                 2.28E−06 
                 1.70E+05 
                 3.88E−02 
               
               
                 S156I 
                 hPD-L1-His 
                 2.15E−08 
                 3.34E+05 
                 7.17E−03 
               
               
                 A165S 
                 hPD-L1-His 
                 1.99E−08 
                 2.87E+05 
                 5.71E−03 
               
               
                 S131A 
                 hPD-L1-His 
                 low 
                 low 
                 low 
               
               
                 S156I/A165S 
                 hPD-L1-His 
                 2.07E−08 
                 2.67E+05 
                 5.53E−03 
               
               
                 S156I/S131A 
                 hPD-L1-His 
                 1.39E−08 
                 2.32E+05 
                 3.23E−03 
               
               
                 A165S/S131A 
                 hPD-L1-His 
                 4.00E−08 
                 2.42E+05 
                 9.70E−03 
               
               
                 S156I/A165S/S131A 
                 hPD-L1-His 
                 3.20E+08 
                 2.49E+05 
                 7.98E−03 
               
               
                 S156F 
                 hPD-L1-His 
                 2.56E−08 
                 2.54E+05 
                 6.52E−03 
               
               
                 S156R 
                 hPD-L1-His 
                 4.61E−08 
                 2.51E+05 
                 1.16E−02 
               
               
                 S156E 
                 hPD-L1-His 
                 3.16E−08 
                 2.76E+05 
                 8.74E−03 
               
               
                 S156D 
                 hPD-L1-His 
                 2.60E−08 
                 2.46E+05 
                 6.41E−03 
               
               
                 S156Q 
                 hPD-L1-His 
                 low 
                 low 
                 low 
               
               
                 S131V 
                 hPD-L1-His 
                 8.95E−08 
                 1.62E+05 
                 1.45E−02 
               
               
                 S131I 
                 hPD-L1-His 
                 2.53E−08 
                 2.61E+05 
                 6.59E−03 
               
               
                 S131F 
                 hPD-L1-His 
                 3.38E−08 
                 3.42E+05 
                 1.16E−02 
               
               
                 S131R 
                 hPD-L1-His 
                 3.40E−08 
                 2.54E+05 
                 8.62E−03 
               
               
                 S131E 
                 hPD-L1-His 
                 2.87E−08 
                 2.86E+05 
                 8.20E−03 
               
               
                 S131D 
                 hPD-L1-His 
                 4.67E−08 
                 2.39E+05 
                 1.11E−02 
               
               
                 S131Q 
                 hPD-L1-His 
                 4.00E−08 
                 2.42E+05 
                 9.67E−03 
               
               
                 A165V 
                 hPD-L1-His 
                 1.07E−07 
                 2.73E+05 
                 2.93E−02 
               
               
                 A165I 
                 hPD-L1-His 
                 2.47E−08 
                 4.79E−05 
                 1.18E−02 
               
               
                 A165F 
                 hPD-L1-His 
                 4.18E−08 
                 3.91E+05 
                 1.63E−02 
               
               
                 A165R 
                 hPD-L1-His 
                 3.48E−08 
                 3.29E+05 
                 1.14E−02 
               
               
                 A165E 
                 hPD-L1-His 
                 3.70E−08 
                 4.44E+06 
                 1.64E−02 
               
               
                 A165D 
                 hPD-L1-His 
                 4.37E−08 
                 3.33E+06 
                 1.45E−02 
               
               
                 A165Q 
                 hPD-L1-His 
                 8.26E−08 
                 2.99E+06 
                 2.47E−02 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Kinetic affinities of CD80 variants to CD28 
               
            
           
           
               
               
               
               
               
            
               
                 Sample ID 
                 Ligand 
                 Kd (M) 
                 Kon(1/Ms) 
                 Kdis(1/s) 
               
               
                   
               
               
                 WT 
                 hCD28-His 
                 1.81E−08 
                 6.07E+05 
                 0.011 
               
               
                 S131V 
                 hCD28-His 
                 1.90E−08 
                 1.79E+06 
                 3.41E−02 
               
               
                 V155A 
                 hCD28-His 
                 4.29E−08 
                 1.33E+06 
                 5.72E−02 
               
               
                 V155I 
                 hCD28-His 
                 8.63E−09 
                 3.04E+06 
                 2.62E−02 
               
               
                 V155T 
                 hCD28-His 
                 9.61E−09 
                 2.41E+06 
                 2.32E−02 
               
               
                 V166A 
                 hCD28-His 
                 2.58E−08 
                 1.71E+06 
                 4.42E−02 
               
               
                 V166T 
                 hCD28-His 
                 2.58E−08 
                 1.58E+06 
                 4.06E−02 
               
               
                 V166L/L139V 
                 hCD28-His 
                 1.36E−08 
                 2.24E+06 
                 3.06E−02 
               
               
                 S156A/V155A 
                 hCD28-His 
                 1.68E−07 
                 4.74E+05 
                 7.97E−02 
               
               
                 S156A/V155I 
                 hCD28-His 
                 2.77E−08 
                 1.45E+06 
                 4.00E−02 
               
               
                 S156A/V155T 
                 hCD28-His 
                 8.26E−09 
                 4.40E+06 
                 3.64E−02 
               
               
                 S156A/T130A 
                 hCD28-His 
                 5.39E−09 
                 3.30E+06 
                 1.78E−02 
               
               
                 S156A/V166A 
                 hCD28-His 
                 2.32E−07 
                 1.81E+05 
                 4.21E−02 
               
               
                 S156A/V166L/L139V 
                 hCD28-His 
                 2.10E−08 
                 1.95E+06 
                 4.10E−02 
               
               
                 S156I 
                 hCD28-His 
                 1.50E−08 
                 1.85E+06 
                 2.78E−02 
               
               
                 A165S 
                 hCD29-His 
                 1.14E−08 
                 2.32E+06 
                 2.65E−02 
               
               
                 S131A 
                 hCD28-His 
                 4.40E−06 
                 2.98E+04 
                 1.31E−01 
               
               
                 S156I/A165S 
                 hCD28-His 
                 2.57E−09 
                 3.53E+06 
                 9.07E−03 
               
               
                 S156I/S131A 
                 hCD28-His 
                 3.67E−09 
                 3.27E+06 
                 1.20E−02 
               
               
                 A165S/S131A 
                 hCD28-His 
                 8.79E−09 
                 2.45E+06 
                 2.15E−02 
               
               
                 S156I/A165S/S131A 
                 hCD28-His 
                 3.45E−09 
                 3.02E+06 
                 1.04E−02 
               
               
                 S156F 
                 hCD28-His 
                 1.74E−08 
                 2.00E+06 
                 3.48E−02 
               
               
                 S156R 
                 hCD28-His 
                 1.11E−08 
                 2.62E+06 
                 2.90E−02 
               
               
                 S156E 
                 hCD28-His 
                 5.94E−09 
                 3.45E+06 
                 2.05E−02 
               
               
                 S156D 
                 hCD28-His 
                 4.64E−09 
                 3.74E+06 
                 1.73E−02 
               
               
                 S156Q 
                 hCD28-His 
                 low 
                 low 
                 low 
               
               
                 S131V 
                 hCD28-His 
                 5.32E−09 
                 2.03E+06 
                 1.08E−02 
               
               
                 S131I 
                 hCD28-His 
                 6.60E−09 
                 1.78E+06 
                 1.18E−02 
               
               
                 S131F 
                 hCD28-His 
                 2.06E−08 
                 1.56E+06 
                 3.20E−02 
               
               
                 S131R 
                 hCD28-His 
                 1.17E−08 
                 2.47E+06 
                 2.90E−02 
               
               
                 S131E 
                 hCD28-His 
                 7.69E−09 
                 3.44E+06 
                 2.65E−02 
               
               
                 S131D 
                 hCD28-His 
                 6.95E−09 
                 3.16E+06 
                 2.20E−02 
               
               
                 S131Q 
                 hCD28-His 
                 1.01E−08 
                 2.96E+06 
                 3.00E−02 
               
               
                 A165V 
                 hCD28-His 
                 2.04E−08 
                 1.87E+06 
                 3.82E−02 
               
               
                 A165I 
                 hCD28-His 
                 1.96E−07 
                 5.28E+05 
                 1.03E−01 
               
               
                 A165F 
                 hCD28-His 
                 2.04E−08 
                 1.50E+06 
                 3.06E−02 
               
               
                 A165R 
                 hCD28-His 
                 4.03E−08 
                 1.80E+06 
                 7.27E−02 
               
               
                 A165E 
                 hCD28-His 
                 2.06E−08 
                 3.01E+06 
                 6.19E−02 
               
               
                 A165D 
                 hCD28-His 
                 1.13E−08 
                 3.46E+06 
                 3.91E−02 
               
               
                 A165Q 
                 hCD28-His 
                 1.79E−08 
                 3.02E+06 
                 5.41E−02 
               
               
                   
               
            
           
         
       
     
     Example 3 
     Assessment of Cell Surface Binding Affinities of CD80 Variants by FACS 
     (1) Generation of Stable Cells Overexpressing Target of Interest (hCTLA-4, hCD28, and hPD-L1) using Flp-In™ Cell Line for FACS Assay 
     The Expression Vector containing polynucleotide encoding hCD28, hCTLA-4, or hPD-L1 was co-transfected with a 9:1 ratio of pOG44:pcDNATM5/FRT plasmid into mammalian Flp-In™ 293 host cells (Invitrogen). Twenty-four hours after transfection, the cells were washed and fresh medium were added to the cells. Hygromycin B (at 200 ug/mL final concentration) was added to the transfected cells 48 hours after transfection. The medium containing 200 ug/mL hygromycin B was changed every 5 days until single clone was selected. All the single clones were analyzed by FACS binding assays. The best expressing single clones for hCD28, hCTLA-4 and hPD-L1, respectively were expanded, and preserved in the freezing medium containing D-MEM (high glucose), 10% FBS, 2 mM L-glutamine, and 1% Pen-Strep in liquid nitrogen. The three stable cell lines were characterized by FACS binding assay as described below. 
     (2) Cell Surface Binding Assay by FACS 
     The binding affinity (EC50) of CD80 variants to Flp-in 293 cells overexpressing CD28, Flp-in 293 cells overexpressing CTLA4 and Flp-in 293 cells overexpressing PD-L1, respectively were determined by FACS. The FACS binding assays were performed as follows: Flp-in 293 cells overexpressing CD28, Flp-in 293 cells overexpressing CTLA4 and Flp-in 293 cells overexpressing PD-L1 were stained with a serial diluted mutant CD80-Fc fusion protein on ice for 1 hour, (i) with concentrations of 100 ug/ml, 30 ug/ml, 10 ug/ml, 3 ug/ml, 1 ug/ml, 0.3 ug/ml, 0.1 ug/ml, and 0.03 ug/m1 for either Flp-in 293 cells overexpressing CD28 or Flp-in 293 cells overexpressing PD-L1, and (ii) with concentrations of 3 ug/ml, 1 ug/ml, 0.3 ug/ml, 0.1 ug/ml, 0.03 ug/ml, 0.01 ug/ml, 0.03μg/ml, and 0.001 ug/m1 for Flp-in 293 cells overexpressing CTLA4. The cells were washed with staining buffer (PBS +2% fetal bovine serum) to remove free CD80-Fc Fusion Proteins, and then stained with AlexFluor 488-conjugated anti-human IgG antibody for 30 min on ice. The cells were washed and analyzed by FACS. 
     The results of cell surface binding affinity assays by FACS were presented in  FIGS. 20A-20B  (binding affinity of CD80 variants to CTLA-4-overexpressing Flp-in 293 cells). Tables 10 and 11 summarize results of cell surface binding affinity assays presented in  FIGS. 20A-20B  with top MFI (Mean Fluorescence Intensity) values of each tested CD80-Fc Fusion protein including single, double and triple mutations (e.g. S1561/A165S, S1561/S131A, A165S/S131A, S1561/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with EC 50  (ug/ml) values. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results of cell surface binding affinity assays by FACS were presented in  FIGS. 21A-21B  (binding affinity of CD80 variants to CD28-overexpressing Flp-in 293 cells). Tables 12 and 13 summarize results of cell surface binding affinity assays presented in  FIGS. 21A-21B  with top MFI (Mean Fluorescence Intensity) values of each tested CD80-Fc Fusion protein including single, double and triple mutations (e.g. S1561/A165S, S156I/S131A, A165S/S131A, S1561/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with EC50 (ug/ml) values. The EC50 (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 10 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
                 WT 
                 8526 
                 0.034 
               
               
                   
                 S156I/A165S 
                 8379 
                 0.040 
               
               
                   
                 S156I/S131A 
                 7955 
                 0.013 
               
               
                   
                 A165S/S131A 
                 7821 
                 0.036 
               
               
                   
                 S156I/A165S/S131A 
                 8071 
                 0.031 
               
               
                   
                 S156F 
                 8432 
                 0.068 
               
               
                   
                 S156R 
                 8478 
                 0.027 
               
               
                   
                 S156E 
                 8794 
                 0.008 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 11 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
                 WT 
                 11890 
                 0.014 
               
               
                   
                 S156D 
                 11950 
                 0.017 
               
               
                   
                 S156Q 
                 11958 
                 0.023 
               
               
                   
                 S131V 
                 11719 
                 0.038 
               
               
                   
                 S131I 
                 11772 
                 0.028 
               
               
                   
                 S131F 
                 11911 
                 0.046 
               
               
                   
                 S131R 
                 11766 
                 0.034 
               
               
                   
                 S131E 
                 12056 
                 0.042 
               
               
                   
                 S131D 
                 11728 
                 0.069 
               
               
                   
                 S131Q 
                 11827 
                 0.029 
               
               
                   
                 A165V 
                 11769 
                 0.081 
               
               
                   
                 A165I 
                 10839 
                 0.124 
               
               
                   
                 A165F 
                 11308 
                 0.046 
               
               
                   
                 A165R 
                 11821 
                 0.032 
               
               
                   
                 A165E 
                 11931 
                 0.040 
               
               
                   
                 A165D 
                 12118 
                 0.030 
               
               
                   
                 A165Q 
                 11980 
                 0.043 
               
               
                   
                   
               
            
           
         
       
     
     The results of cell surface binding affinity assays by FACS were presented in  FIGS. 22A-22B  (binding affinity of CD80 variants to PD-L1-overexpressing Flp-in 293 cells). Tables 14 and 15 summarize results of cell surface binding affinity assays presented in  FIGS. 22A-22B  with top MFI (Mean Fluorescence Intensity) values of each tested CD80-Fc Fusion protein including single, double and triple mutations (e.g. S1561/A165S, S1561/S131A, A165S/S131A, S1561/A165S/S131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with EC50 (ug/ml) values. The EC50 (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     As seen in  FIGS. 25-27 , the FACS binding EC50 of mutant CD8O-Fc Fusion Proteins showed differentiation of binding affinity to CTLA-4, CD28 and PD-L1. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 12 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WT 
                 12650 
                 10 
               
               
                   
                 S156I/A165S 
                 11348 
                 9.2 
               
               
                   
                 S156I/S131A 
                 10810 
                 9.2 
               
               
                   
                 A165S/S131A 
                 10150 
                 6.3 
               
               
                   
                 S156I/A165S/ 
                 10155 
                 7.7 
               
               
                   
                 S131A 
                   
                   
               
               
                   
                 S156F 
                 10700 
                 9.2 
               
               
                   
                 S156R 
                 9437 
                 12.5 
               
               
                   
                 S156E 
                 10252 
                 9.8 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 13 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WT 
                 11800 
                 8.5 
               
               
                   
                 S156D 
                 11050 
                 10.8 
               
               
                   
                 S156Q 
                 10562 
                 8.6 
               
               
                   
                 S131V 
                 7493 
                 11.4 
               
               
                   
                 S131I 
                 8861 
                 8.4 
               
               
                   
                 S131F 
                 6007 
                 15.9 
               
               
                   
                 S131R 
                 10824 
                 12.2 
               
               
                   
                 S131E 
                 11296 
                 7.9 
               
               
                   
                 S131D 
                 9064 
                 9.5 
               
               
                   
                 S131Q 
                 10113 
                 9.9 
               
               
                   
                 A165V 
                 8281 
                 15.2 
               
               
                   
                 A165I 
                 4820 
                 41.8 
               
               
                   
                 A165F 
                 6674 
                 18.7 
               
               
                   
                 A165R 
                 7566 
                 13.9 
               
               
                   
                 A165E 
                 12093 
                 10.7 
               
               
                   
                 A165D 
                 8417 
                 13.2 
               
               
                   
                 A165Q 
                 8894 
                 12.7 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 15 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WT 
                 11020 
                 8.5 
               
               
                   
                 S156D 
                 8379 
                 8.3 
               
               
                   
                 S156Q 
                 8323 
                 8 
               
               
                   
                 S131V 
                 7634 
                 9.2 
               
               
                   
                 S131I 
                 8699 
                 8.1 
               
               
                   
                 S131F 
                 3902 
                 5.6 
               
               
                   
                 S131R 
                 12302 
                 8.1 
               
               
                   
                 S131E 
                 6275 
                 16.5 
               
               
                   
                 S131D 
                 5994 
                 11.5 
               
               
                   
                 S131Q 
                 9317 
                 9.9 
               
               
                   
                 A165V 
                 6136 
                 6.9 
               
               
                   
                 A165I 
                 3622 
                 8.9 
               
               
                   
                 A165F 
                 6053 
                 7.6 
               
               
                   
                 A165R 
                 12635 
                 6.3 
               
               
                   
                 A165E 
                 6633 
                 13.4 
               
               
                   
                 A165D 
                 7152 
                 9.4 
               
               
                   
                 A165Q 
                 10717 
                 8.3 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 14 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (MFI) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WT 
                 7361 
                 3.9 
               
               
                   
                 S156I/A165S 
                 7238 
                 7.8 
               
               
                   
                 S156I/S131A 
                 6830 
                 4.3 
               
               
                   
                 A165S/S131A 
                 7193 
                 9.3 
               
               
                   
                 S156I/A165S/S131A 
                 7981 
                 6.7 
               
               
                   
                 S156F 
                 7817 
                 19.8 
               
               
                   
                 S156R 
                 7921 
                 5.8 
               
               
                   
                 S156E 
                 8184 
                 7.7 
               
               
                   
                   
               
            
           
         
       
     
     Example 4 
     Functional Study of CD80 Variants for T-cell Activation 
     (1) IL-2 release assay 
     To test CD80-induced IL-2 production in Jurkat T-cells, IL-2 release assay was performed as follows: 3.2×10 5 /well JurkaT-cells were seeded in a 96-well plate. Serial dilutions of each CD80 mutant protein were added to a final concentrations of 30 μg/ml, 10 μg/ml, 3 μg/ml, 1 μg/ml, 0.3 μg/ml, 0.1 μg/ml, 0.03 μg/m1 and 0.01 μg/ml. PHA (phytohemagglutinin) was added to each well with final a concentration of 10 μg/ml. The cells were incubated at 37° C. for 24 hours and the supernatant were harvested for ELISA assay. The Human IL-2 Uncoated ELISA kit (Invitrogen #88-7025) was used to quantitate IL-2 in the supernatant. ELISA plate was coated with 50 μL/well of capture antibody overnight at 4° C. The plate was washed and blocked at room temperature for 1 hour. After washing, 50 μL/well of the above supernatant was added to the appropriate wells and incubated at room temperature for 2 hours. The plate was then washed and 50 μL/well of detection antibody was added and incubated at room temperature for 1 hour. After washing, 50 μL/well of Avidin-HRP was added and incubated at room temperature for 30 minutes. The plate was washed seven times and 50 μl of TMB Substrate was added to each well, and the reactions were stopped by addition of 25 μl of stop solution. OD 450  was measured using a microplate reader. 
       FIGS. 23A-23D  presents results of functional assays for IL-2 release to test ability of variant CD80-Fc Fusion Proteins for T-cell activation. Table 16 summarizes results of T-cell activation assays measured by IL2 release presented in  FIGS. 23A-23D  with top OD450 values of each tested CD8O-Fc Fusion protein including single, double and triple mutations (e.g. 51561/A1655, 51561/5131A, A1655/5131A, 51561/A1655/5131A, S156F, S156R, S156E, S156D, S156Q, S131V, S131I, S131F, S131R, S131E, S131D, S131Q, A165V, A165I, A165F, A165R, A165E, A165D, and A165Q), along with EC 50  (ug/ml) values. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results from JurkaT-cell IL-2 release assay as shown in  FIGS. 23A -23D and presented in Table 16 indicate mutations in IgC domain can influence the ability of CD80 to activate T-cell. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 16 
               
               
                   
                   
               
               
                   
                   
                 Top 
                 EC50 
               
               
                   
                   
                 (OD450) 
                 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 WT 
                 2.64 
                 0.94 
               
               
                   
                 S156I/A165S 
                 2.52 
                 1.26 
               
               
                   
                 S156I/S131A 
                 2.43 
                 1.68 
               
               
                   
                 A165S/S131A 
                 2.60 
                 1.29 
               
               
                   
                 S156I/A165S/S131A 
                 2.47 
                 1.78 
               
               
                   
                 S156F 
                 2.03 
                 3.63 
               
               
                   
                 S156R 
                 2.29 
                 3.99 
               
               
                   
                 S156E 
                 2.23 
                 1.46 
               
               
                   
                 S156D 
                 2.56 
                 0.66 
               
               
                   
                 S156Q 
                 2.66 
                 0.97 
               
               
                   
                 S131V 
                 2.40 
                 4.59 
               
               
                   
                 S131I 
                 2.61 
                 1.13 
               
               
                   
                 S131F 
                 0.90 
                 66.84 
               
               
                   
                 S131R 
                 2.71 
                 0.79 
               
               
                   
                 S131E 
                 2.72 
                 0.76 
               
               
                   
                 S131D 
                 2.26 
                 4.27 
               
               
                   
                 S131Q 
                 2.70 
                 1.04 
               
               
                   
                 A165V 
                 2.11 
                 61.46 
               
               
                   
                 A165I 
                 0.80 
                 7.43 
               
               
                   
                 A165F 
                 1.30 
                 10.65 
               
               
                   
                 A165R 
                 2.34 
                 9.85 
               
               
                   
                 A165E 
                 2.71 
                 0.54 
               
               
                   
                 A165D 
                 2.32 
                 38.12 
               
               
                   
                 A165Q 
                 2.61 
                 1.65 
               
               
                   
                 hIgG 
                 0.71 
                 — 
               
               
                   
                   
               
            
           
         
       
     
     (2) Checkpoint Blockade Reporter Assays: 
     The CD80 variants were evaluated by checkpoint blockade reporter assay using Promega&#39;s assay kits. For CTLA-4 blockade assay, the CTLA-4/Jurkat Effector Cells and aAPC/Raji Cells were thawed at room temperature. Equilibrated the Bio-Glo™ Luciferase Assay Buffer to ambient temperature, protected from light. and then transfered all of the Bio-Glo™ Luciferase Assay Buffer into the amber bottle containing the Bio-Glo™ Luciferase Assay Substrate and mixed by inversion until the Substrate was thoroughly dissolved. Preparing and Plating CTLA-4 Effector Cells should be performed using aseptic technique in a sterile cell culture hood if setting up a 16-hour assay. For a 6-hour assay, the setup may be performed on the bench. 
     3.2 ml of prewarmed (37° C.) assay buffer was added to a 15 ml conical tube. One vial of CTLA-4 Effector Cells was removed from storage and transferred to the bench on dry ice. The cells were warmed in a 37° C. water bath until being just thawed (about 2-3 minutes). The cell suspension was gently mixed and the cells (0.8 ml) were transferred to the 15m1 conical tube containing 3.2 ml of assay buffer. After mixing well by gently inverting or pipetting 1-2 times, the cell suspension was transferred to a sterile reagent reservoir. Using a multichannel pipette, 25 μl of the cell suspension was immediately dispensed to each of the inner 60 wells of two 96-well, solid, white, flat-bottom assay plates. 75 μl of assay buffer was added to each of the outside wells of the assay plates. The assay plates were covered with a lid and keep at ambient temperature (22-25° C.). 
     Using a multichannel pipette, 25 μl of the appropriate antibody dilution was added to the plated CTLA-4 Effector Cells according to the plate. The assay plates were covered with a lid and are kept at ambient temperature (22° -25° C.) while preparing the aAPC/Raji Cells. 
     Preparing and Plating aAPC/Raji Cells 
     The thaw-and-use aAPC/Raji Cells included in this kit are sensitive, and care should be taken to follow the cell thawing and plating procedures exactly as described. The cell reagents should not be overmixed or overwarmed. 7.2 ml of prewarmed (37° C.) assay buffer was added to a 15ml conical tube. One vial of aAPC/Raji Cells was removed from storage at −140° C. and transferred to the bench on dry ice. The cells were thawed in a 37° C. water bath until just thawed (about 2-3 minutes). The cells (0.8 ml) was transferred to the 15 ml conical tube containing 7.2 ml assay buffer. After mixing well by gently inverting or pipetting 1-2 times, the cell suspension was transferred to a sterile reagent reservoir. Using a multichannel pipette, 25 μl of the cell suspension was immediately dispensed to the pre-plated CTLA-4 Effector Cells and Anti-CTLA-4 Control Antibody. The final assay volume was 750 The assay plates were covered with a lid and incubate for 6 hours in a 37° C., 5% CO2 incubator. 
     Note: The 6-hour assay time was optimized for maximum luminescence signal. Optimizing the assay time (6-16 hours) is recommended for optimal assay response. Plating CTLA-4 Effector Cells and aAPC/Raji Cells as indicated will result in a 2:1 ratio of Effector:Target cells. If higher luminescence signals are desired, the dilution volume of the aAPC/Raji Cells may be halved to attain a 1:1 ratio of Effector:Target cells. 
     Adding Bio-Glo™ Reagent 
     Bio-Glo™ Reagent should be at ambient temperature (22-25° C.) when added to assay plates. The assay plates were removed from the incubator and were equilibrated to ambient temperature for 10-15 minutes. Using a manual multichannel pipette, 75 μl of Bio-Glo™ Reagent was added to the inner 60 wells of the assay plates, taking care not to create bubbles. 75 μl of Bio-Glo™ Reagent was added to wells B1, C1 and D1 of each assay plate to measure the background signal and was incubated at ambient temperature for 5-15 minutes. Luminescence was measured using a luminometer luminescence plate reader. 
       FIGS. 25A-25L  presents results of CTLA-4 blockade assay to evaluate the ability of variant CD8O-Fc Fusion Proteins blocking CTLA-4/CD28 interaction function. Table 17 summarizes results of CTLA-4 blockade assay presented in  FIGS. 25A -25L with EC 50  (ug/ml) values. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 17 
               
               
                   
                   
               
               
                   
                   
                 EC50 
               
               
                   
                   
                 (ug/mL) 
               
               
                   
                   
               
             
            
               
                   
                 WT 
                 0.243 
               
               
                   
                 S156I/A165S 
                 0.217 
               
               
                   
                 S156I/S131A 
                 0.309 
               
               
                   
                 A165S/S131A 
                 0.868 
               
               
                   
                 S156I/A165S/S131A 
                 0.227 
               
               
                   
                 S156F 
                 1.187 
               
               
                   
                 S156R 
                 0.361 
               
               
                   
                 S156E 
                 0.363 
               
               
                   
                 S156D 
                 0.474 
               
               
                   
                 S156Q 
                 1.578 
               
               
                   
                 S131V 
                 4.311 
               
               
                   
                 S131I 
                 0.485 
               
               
                   
                 S131F 
                 0.474 
               
               
                   
                 S131R 
                 0.283 
               
               
                   
                 S131E 
                 0.431 
               
               
                   
                 S131D 
                 0.382 
               
               
                   
                 S131Q 
                 0.209 
               
               
                   
                 A165V 
                 0.296 
               
               
                   
                 A165I 
                 2.432 
               
               
                   
                 A165F 
                 0.323 
               
               
                   
                 A165R 
                 0.227 
               
               
                   
                 A165E 
                 1.039 
               
               
                   
                 A165D 
                 0.210 
               
               
                   
                 A165Q 
                 0.136 
               
               
                   
                 S131V 
                 0.106 
               
               
                   
                 V155A 
                 0.126 
               
               
                   
                 V155I 
                 0.191 
               
               
                   
                 V155T 
                 0.097 
               
               
                   
                 V166A 
                 0.541 
               
               
                   
                 V166T 
                 0.151 
               
               
                   
                 V166L/L139V 
                 0.124 
               
               
                   
                 S156A/V155A 
                 0.250 
               
               
                   
                 S156A/V155I 
                 0.118 
               
               
                   
                 S156A/V155T 
                 0.036 
               
               
                   
                 S156A/T130A 
                 0.121 
               
               
                   
                 S156A/V166A 
                 0.281 
               
               
                   
                 S156A/V166L/ 
                 0.187 
               
               
                   
                 L139V 
                   
               
               
                   
                 S156I 
                 0.134 
               
               
                   
                 A165S 
                 0.168 
               
               
                   
                 S156A 
                 0.311 
               
               
                   
                 S131A 
                 0.187 
               
               
                   
                 S156V 
                 0.134 
               
               
                   
                 S156L 
                 0.168 
               
               
                   
                 S156I 
                 0.311 
               
               
                   
                   
               
            
           
         
       
     
     Example 5 
     Co-Stimulation Activity of CD80 Variants 
     TCR/CD3 Effector (IL-2) cells (Promega) were used to evaluate co-stimulation activity of CD80 variants. 
     Briefly, TCR/CD3 effector (IL-2) cells were expanded freshly before the assay setup. TCR/CD3 effector (IL-2) cells were prepared at 2×10 6  cells/mL in RPMI-1640 with 10%FBS. For one 96-well plate, 5 mL of cell suspension were added with 1 ug/mL of mouse anti-human CD3 antibody (OKT3, BioLeged Cat #317326) and 150 uL of goat anti-hulgG beads (AbraMag: Cat #PN544060). The mixture of cell, antibody and beads was distributed on an opaque 96-well plate at 50 uL/well. To prepare testing compounds, CD80-Fc wild-type (WT) and CD80-Fc variants, were prepared at 30 ug/mL and their duplicate 1:3 serial dilutions. 25 μl testing compounds were transferred to each well, with final volume of 75 μl/well on the plate. Blank wells were added with 75 μl of medium for measuring background readings. The plates were incubated at 37° C., 5% CO 2  incubator for 6 hours. After incubation, 75 μl of Bio-Glo™ Reagent (Promega) were added into each well of the assay plates, incubated at ambient temperature for 3 minutes. The Relative Luminescence Unit (RLU) readings were measured using a luminescence plate reader (CLARIOstar, BMG LABTECH). 
     The Relative Luminescence Unit (RLU) readings were plotted with GraphPad Prism® software and analyzed with program of [Agonist] vs. response—Variable slope (four parameters) —Least squares fit to determine the EC50 values. 
       FIGS. 26A -26H presents results of co-stimulation activity of variant CD80-Fc Fusion Proteins. Table 18 summarizes results presented in  FIGS. 26A -26H with EC 50  (ug/ml) values. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 18 
               
               
                   
                   
               
               
                   
                   
                 EC50 (ug/ml) 
               
               
                   
                   
               
             
            
               
                   
                 CD80 (WT) 
                 0.4371 
               
               
                   
                 S156I/A165S 
                 0.1501 
               
               
                   
                 S156I/S131A 
                 0.1439 
               
               
                   
                 A165S/S131A 
                 0.1876 
               
               
                   
                 S156I/A165S/S131A 
                 0.1631 
               
               
                   
                 S156F 
                 0.1596 
               
               
                   
                 S156R 
                 0.2163 
               
               
                   
                 S156E 
                 0.2038 
               
               
                   
                 S156D 
                 0.2357 
               
               
                   
                 S156Q 
                 0.2469 
               
               
                   
                 S131V 
                 0.2515 
               
               
                   
                 S131I 
                 0.2631 
               
               
                   
                 S131F 
                 0.3372 
               
               
                   
                 S131R 
                 0.3081 
               
               
                   
                 S131E 
                 0.2341 
               
               
                   
                 S131D 
                 0.2581 
               
               
                   
                 S131Q 
                 0.1705 
               
               
                   
                 A165V 
                 0.3016 
               
               
                   
                 A165I 
                 0.4600 
               
               
                   
                 A165F 
                 0.3154 
               
               
                   
                 A165R 
                 0.1973 
               
               
                   
                 A165E 
                 0.2215 
               
               
                   
                 A165D 
                 0.1658 
               
               
                   
                 A165Q 
                 0.1259 
               
               
                   
                 S156A 
                 0.2442 
               
               
                   
                 A165S 
                 0.1369 
               
               
                   
                 S131A 
                 0.1450 
               
               
                   
                 S156V 
                 0.1298 
               
               
                   
                 S156L 
                 0.1023 
               
               
                   
                 S131V 
                 0.1216 
               
               
                   
                 V155A 
                 0.1239 
               
               
                   
                 V155I 
                 0.1241 
               
               
                   
                 V155T 
                 0.1718 
               
               
                   
                 V166A 
                 0.2139 
               
               
                   
                 V166T 
                 0.1839 
               
               
                   
                 V166L/L139V 
                 0.1861 
               
               
                   
                 S156A/V155A 
                 0.2243 
               
               
                   
                 S156A/V155I 
                 0.1467 
               
               
                   
                 S156A/V155T 
                 0.0643 
               
               
                   
                 S156A/T130A 
                 0.1541 
               
               
                   
                 S156A/V166A 
                 0.7127 
               
               
                   
                 S156A/V166L/L139V 
                 0.1900 
               
               
                   
                 S156I 
                 0.1259 
               
               
                   
                 A165S 
                 0.0993 
               
               
                   
                   
               
            
           
         
       
     
     Example 6 
     In Vivo Efficacy Evaluation of Mutant CD80 in Tumor Growth 
     (1) Inhibition in CT26 Syngeneic Mouse Model 
     Efficacy evaluation of CD80 variants in tumor growth inhibition was tested in CT26 syngeneic mouse model. CT26 cells were inoculated subcutaneously into seven Balb/c mice at 1.0×10 6  cells/mouse. Mice were monitored for tumor growth three times per week. 
     Mice were randomly assigned to different groups (n=7 mice per experimental group) when the mean tumor volume reached about 60-100 mm 3 . These tumor bearing mice were treated with CD80 variant at lmg/kg at day 0, day 3 and day 7 by intravenous injection. Tumors and body weights were measured three times per week to monitor the efficacy and toxicity. 
       FIGS. 27  presents results of the antitumor activity of CD80 variants in CT26 syngeneic mouse model. 
     (2) Inhibition in MC-38 Syngeneic Mouse Model 
     Efficacy evaluation of CD80 variants in tumor growth inhibition was tested in MC-38 syngeneic mouse model. MC-38 cells were inoculated subcutaneously into seven C57BL/6 mice at 1.0×10 6  cells /mouse. Mice were monitored for tumor growth twice per week. 
     Mice were randomly assigned to different groups (n=7 mice per experimental group) when the mean tumor volume reached about 90 mm 3 . These tumor bearing mice were treated with CD80 variant at 150 μg/mouse at day 1, day 4 and day 8 by intravenous injection. Tumors and body weights were measured twice per week to monitor the efficacy and toxicity. 
       FIGS. 28  presents results of the antitumor activity of CD80 variants in MC-38 syngeneic mouse model. 
     Example 7 
     Assessment of Binding Affinities of Mouse CD80 Variants to Mouse CD28, Mouse PD-L1, and Mouse CTLA-4 by ELISA 
     The binding of mouse CD80 variants to mouse CD28, mouse PD-L1 and mouse CTLA-4, respectively, was ranked with wild-type mCD80 as reference sample tested on the same ELISA plate. This study is a surrogate for a human study. Variants of mouse CD80 are made, the wild type mouse CD80 is presented in  FIG. 14B . 
     The results of binding affinity assays by ELISA were presented in  FIGS. 29A-29D  (binding affinity of mouse CD80 variants to mouse CD28). Table 19 summarizes results of binding assays presented in  FIGS. 29A-29D  with EC 50  (ug/ml) values of each tested mouse CD80-Fc Fusion protein including T165E, T165Q, T165R, T165A, T165S, T165V, T165I, T165F, T165D, S131V, S131I, S131F, S131R, S131E, S131Q, S131A, and S131P. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results of binding affinity assays by ELISA were presented in  FIGS. 30A-30D  (binding affinity of mouse CD80 variants to mouse PD-L1). Table 20 summarizes results of binding assays presented in  FIGS. 30A-30D  with EC 50  (ug/ml) values of each tested mouse CD80-Fc Fusion protein including T165E, T165Q, T165R, T165A, T165S, T165V, T165I, T165F, T165D, S131V, S131I, S131F, S131R, S131E, S131Q, S131A, and S131P. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     The results of binding affinity assays by ELISA were presented in  FIGS. 31A-31D  (binding affinity of mouse CD80 variants to mouse CTLA4). Table 21 summarizes results of binding assays presented in  FIGS. 31A -31D with EC 50  (ug/ml) values of each tested mouse CD80-Fc Fusion protein including T165E, T165Q, T165R, T165A, T165S, T165V, T165I, T165F, T165D, S131V, S131I, S131F, S131R, S131E, S131Q, S131A, and S131P. The EC 50  (ug/ml) is the concentration or value of a protein that gives half maximal response in the binding assay. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 19 
               
               
                   
                   
               
               
                   
                   
                 EC50 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 A. mCD80(WT) 
                 3.606 
               
               
                   
                 mCD80(T165E) 
                 10.59 
               
               
                   
                 mCD80(T165Q) 
                 3.462 
               
               
                   
                 mCD80(T165R) 
                 6.914 
               
               
                   
                 mCD80(T165A) 
                 5.705 
               
               
                   
                 mCD80(T165S) 
                 1.603 
               
               
                   
                 B. mCD80(WT) 
                 3.499 
               
               
                   
                 mCD80(T165V) 
                 17.56 
               
               
                   
                 mCD80(T165I) 
                 17.69 
               
               
                   
                 mCD80(T165F) 
                 18.27 
               
               
                   
                 mCD80(T165D 
                 10.37 
               
               
                   
                 mCD80(S131V) 
                 11.19 
               
               
                   
                 C. mCD80(WT) 
                 5.467 
               
               
                   
                 mCD80(S131I) 
                 19.25 
               
               
                   
                 mCD80(S131F) 
                 3.485 
               
               
                   
                 mCD80(S131R) 
                 5.127 
               
               
                   
                 mCD80(S131E) 
                 3.755 
               
               
                   
                 mCD80(S131Q) 
                 2.879 
               
               
                   
                 D. mCD80(WT) 
                 4.343 
               
               
                   
                 mCD80(S131A) 
                 3.709 
               
               
                   
                 mCD80(S131P) 
                 15.3 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 20 
               
               
                   
                   
               
               
                   
                   
                 EC50 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 A. mCD80(WT) 
                 8.987 
               
               
                   
                 mCD80(T165E) 
                 3.865 
               
               
                   
                 mCD80(T165Q) 
                 4.261 
               
               
                   
                 mCD80(T165R) 
                 4.97 
               
               
                   
                 mCD80(T165A) 
                 4.795 
               
               
                   
                 mCD80(T165S) 
                 6.856 
               
               
                   
                 B. mCD80(WT) 
                 9.688 
               
               
                   
                 mCD80(T165V) 
                 5.873 
               
               
                   
                 mCD80(T165I) 
                 7.567 
               
               
                   
                 mCD80(T165F) 
                 17.13 
               
               
                   
                 mCD80(T165D 
                 5.879 
               
               
                   
                 mCD80(S131V) 
                 6.079 
               
               
                   
                 C. mCD80(WT) 
                 9.914 
               
               
                   
                 mCD80(S131I) 
                 8.58 
               
               
                   
                 mCD80(S131F) 
                 7.044 
               
               
                   
                 mCD80(S131R) 
                 4.661 
               
               
                   
                 mCD80(S131E) 
                 9.23 
               
               
                   
                 mCD80(S131Q) 
                 8.217 
               
               
                   
                 D. mCD80(WT) 
                 8.698 
               
               
                   
                 mCD80(S131A) 
                 8.801 
               
               
                   
                 mCD80(S131P) 
                 6.098 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 21 
               
               
                   
                   
               
               
                   
                   
                 EC50 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 A. mCD80(WT) 
                 0.0535 
               
               
                   
                 mCD80(T165E) 
                 0.1206 
               
               
                   
                 mCD80(T165Q) 
                 0.0827 
               
               
                   
                 mCD80(T165R) 
                 0.1502 
               
               
                   
                 mCD80(T165A) 
                 0.1313 
               
               
                   
                 mCD80(T165S) 
                 0.0633 
               
               
                   
                 B. mCD80(WT) 
                 0.0598 
               
               
                   
                 mCD80(T165V) 
                 0.8854 
               
               
                   
                 mCD80(T165I) 
                 2.079 
               
               
                   
                 mCD80(T165F) 
                 0.172 
               
               
                   
                 mCD80(T165D 
                 0.1538 
               
               
                   
                 mCD80(S131V) 
                 0.2691 
               
               
                   
                 C. mCD80(WT) 
                 0.0508 
               
               
                   
                 mCD80(S131I) 
                 0.4419 
               
               
                   
                 mCD80(S131F) 
                 0.0782 
               
               
                   
                 mCD80(S131R) 
                 0.0748 
               
               
                   
                 mCD80(S131E) 
                 0.0713 
               
               
                   
                 mCD80(S131Q) 
                 0.0596 
               
               
                   
                 D. mCD80(WT) 
                 0.0673 
               
               
                   
                 mCD80(S131A) 
                 0.0924 
               
               
                   
                 mCD80(S131P) 
                 0.6586 
               
               
                   
                   
               
            
           
         
       
     
     Example 8 
     In Vivo Efficacy Evaluation of mouse CD80 variants in Tumor Growth 
     Efficacy evaluation of CD80 variants on tumor growth inhibition can be tested in a CT26 or MC-38 syngeneic mouse model. To test, a mouse CD80 protein is used, as a surrogate for the human protein. To test, CT26 or MC-38 cells are inoculated subcutaneously into mice at 1.0×10 6  cells /mouse. Mice are monitored for tumor growth three times per week. 
     Mice are randomly assigned to different groups (e.g. n=7 mice per experimental group) when the mean tumor volume reaches about 100 mm 3 . These tumor bearing mice are treated with a mouse CD80 variant at lmg/kg at day 0, day 3 and day 7 by intravenous injection. Tumors and body weights are measured three times per week to monitor the efficacy and toxicity. 
     INCORPORATION BY REFERENCE 
     All references, articles, publications, patents, patent publications, and patent applications cited herein are incorporated by reference in their entireties for all purposes. However, mention of any reference, article, publication, patent, patent publication, and patent application cited herein is not, and should not, be taken as an acknowledgment or any form of suggestion that they constitute valid prior art or form part of the common general knowledge in any country in the world.