Patent Publication Number: US-2021179726-A1

Title: Anti-cd27 antibodies and use thereof

Description:
BACKGROUND 
     CD27 is a member of the TNF receptor family and belongs to type I transmembrane glycoprotein. CD27 presents on the cell surface as a pair of disulfide-linked homodimers (van Lier et al., 1987). Unlike other TNF receptor family members, CD27 is constitutively expressed on the surface of T cells, NK cells and some memory B cells (van Lier et al., 1987; Sugita et al., 1992; Xiao et al., 2004). When T cells are activated, the expression of CD27 is up-regulated, thereby having a synergistic co-stimulatory effect on the activation of prion cells. 
     CD70, as a ligand of CD27, interacts with CD27 and recruits intracellular TRAF protein to the intracellular domain of CD27, thereby activating downstream signals, including activation of canonical and non-canonical NF-κB signaling pathways and JNK signaling pathways. It plays an important role in the proliferation, activation and cytotoxicity of CD8 +  T cells (Carr et al., 2006; Rowley and Al-Shamkhani, 2004; Taraban et al., 2006). In addition to expression on normal cells, CD27 is also highly expressed in B-cell lymphomas and B-cell chronic lymphocytic leukemia cells (EA et al., 1995). 
     Previous studies have shown that agonistic antibodies of CD27 could enhance the killing ability of T cells in many mouse tumor models and have anti-tumor activities (Li-zhen He et al., 2013). However, there is still a strong need for CD27 antibodies having better affinity and/or activities. 
     SUMMARY 
     The present disclosure provides an antibody, or an antigen binding fragment or variant thereof, which is capable of binding to CD27 and could exhibit at least one of the following properties: 1) having a high affinity to CD27; 2) specifically binding to human CD27 and monkey CD27; 3) capable of activating and/or increasing CD27 mediated NF-κB activity; 4) capable of stimulating CD4 +  and/or CD8 +  T cell proliferation; 5) capable of stimulating secretion of IFN-γ by CD4 +  and/or CD8 +  T cells; 6) having a relatively high stability; and 7) staying as dimers in solutions during prolonged storage. In addition, the present disclosure also provides a method for preparing and/or using the antibody, or the antigen binding fragment or variant thereof. 
     In one aspect, the present disclosure provides an antibody, or an antigen binding fragment or variant thereof. The antibody, or its fragment or variant could bind to CD27 and exhibit at least one of the following properties: 1) specifically binds to CD27, and does not substantially bind to CD137, OX40 or GITR; 2) binds to CD27 with a K D  of 10 −8  M or less; 3) activates and/or increases CD27 mediated NF-κB activity, as shown in Luciferase Reporter Assay; 4) stimulates CD4 +  and/or CD8 +  T cell proliferation; 5) binds to human CD27 expressed on a cell surface; 6) binds to monkey CD27 expressed on a cell surface; 7) stimulates secretion of IFN-γ by CD4 +  and/or CD8 +  T cells; 8) has a T m  of at least 60° C. as tested by DSC; 9) shows a relative decrease of dimerization of less than about 5% in SEC-HPLC analysis when dissolved in a PBS solution at a concentration of about 10 mg/ml, with a pH of about 7.4, under 45° C., during a course of about 30 days; and 10) shows a change of concentration of less than about 20% when dissolved in a PBS solution at a concentration of about 8-12 mg/ml, with a pH of about 7.4, under 45° C., during a course of about 30 days. 
     In some embodiments, the antibody is selected from the group consisting of: a monoclonal antibody, a chimeric antibody, a humanized antibody, a fully human antibody and a bispecific antibody. 
     In some embodiments, the antigen binding fragment is selected from the group consisting of: a Fab fragment, a Fab′ fragment, a F(ab′)2 fragment, a F(ab)2 fragment, a Fv fragment, and an ScFv. 
     In some embodiments, the variant is selected from the group consisting of: 1) a polypeptide different from the antibody or antigen binding fragment thereof by an addition, deletion or substitution of one or more amino acid; and 2) a polypeptide having a sequence identity of at least 80% with the antibody or antigen binding fragment thereof. 
     In some embodiments, the antibody or the antigen binding fragment or variant thereof competes with a reference antibody for binding to CD27. The reference antibody may comprise: 1) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 8-10 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 5-7 respectively; 2) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 18-20 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 15-17 respectively; 3) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 28-30 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 25-27 respectively; 4) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 38-40 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 35-37 respectively; 5) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 48-50 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 45-47 respectively; 6) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 58-60 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 55-57 respectively; 7) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 68-70 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 65-67 respectively; 8) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 78-80 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 75-77 respectively; 9) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 88-90 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 85-87 respectively; 10) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 3, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 1; 11) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 13, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 11; 12) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 23, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 21; 13) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 33, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 31; 14) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 43, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 41; 15) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 53, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 51; 16) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 63, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 61; 17) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 73, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 71; 18) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 83, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 81; 19) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 115; 20) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 107; 21) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 95; 22) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 99; 23) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 111; 24) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 103; 25) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 113; 26) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 105; 27) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 93; 28) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 97; 29) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 109; or 30) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 101. 
     In some embodiments, the antibody comprises a light chain or a fragment thereof. The light chain or a fragment thereof may comprise a light chain CDR1, and the light chain CDR1 comprises an amino acid sequence selected from SEQ ID NO: 8, 18, 28, 38, 48, 58, 68, 78 and 88. In some embodiments, the light chain or a fragment thereof comprises a light chain CDR2, and the light chain CDR2 comprises an amino acid sequence selected from SEQ ID NO: 9, 19, 29, 39, 49, 59, 69, 79 and 89. In some embodiments, the light chain or a fragment thereof comprises a light chain CDR3, and the light chain CDR3 comprises an amino acid sequence selected from SEQ ID NO: 10, 20, 30, 40, 50, 60, 70, 80 and 90. 
     In some embodiments, the light chain or a fragment thereof comprises a light chain variable region, and the light chain variable region comprises an amino acid sequence selected from SEQ ID NO: 3, 13, 23, 33, 43, 53, 63, 73, 83 and 91. 
     In some embodiments, the light chain or a fragment thereof comprises a light chain constant region, and the light chain constant region comprises a human Igκ constant region. 
     In some embodiments, the light chain or a fragment thereof comprises an amino acid sequence selected from SEQ ID NO: 117, 119, 121, 123, 125, 127, 129, 131 and 133. 
     In some embodiments, the antibody comprises a heavy chain or a fragment thereof. The heavy chain or a fragment thereof may comprise a heavy chain CDR1, and the heavy chain CDR1 comprises an amino acid sequence selected from SEQ ID NO: 5, 15, 25, 35, 45, 55, 65, 75 and 85. In some embodiments, the heavy chain or a fragment thereof comprises a heavy chain CDR2, and the heavy chain CDR2 comprises an amino acid sequence selected from SEQ ID NO: 6, 16, 26, 36, 46, 56, 66, 76 and 86. In some embodiments, the heavy chain or a fragment thereof comprises a heavy chain CDR3, and the heavy chain CDR3 comprises an amino acid sequence selected from SEQ ID NO: 7, 17, 27, 37, 47, 57, 67, 77 and 87. 
     In some embodiments, the heavy chain or a fragment thereof comprises a heavy chain variable region, and the heavy chain variable region comprises an amino acid sequence selected from SEQ ID NO: 1, 11, 21, 31, 41, 51, 61, 71, 81, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113 and 115. 
     In some embodiments, the heavy chain or a fragment thereof comprises a heavy chain constant region, and the heavy chain constant region comprises a human IgG constant region. In some embodiments, the human IgG constant region comprises an IgG1 constant region. 
     In some embodiments, the heavy chain or a fragment thereof comprises an amino acid sequence selected from SEQ ID NO: 118, 120, 122, 124, 126, 128, 130, 132 and 134. 
     In some embodiments, the CD27 is selected from the group consisting of: a human CD27, a mouse CD27 and a monkey CD27. 
     In some embodiments, the antibody or the antigen binding fragment or variant thereof comprises: 1) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 8-10 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 5-7 respectively; 2) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 18-20 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 15-17 respectively; 3) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 28-30 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 25-27 respectively; 4) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 38-40 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 35-37 respectively; 5) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 48-50 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 45-47 respectively; 6) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 58-60 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 55-57 respectively; 7) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 68-70 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 65-67 respectively; 8) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 78-80 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 75-77 respectively; 9) light chain CDR1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 88-90 respectively, and heavy chain CDR 1-3 comprising an amino acid sequence as set forth in SEQ ID NO: 85-87 respectively; 10) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 3, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 1; 11) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 13, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 11; 12) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 23, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 21; 13) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 33, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 31; 14) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 43, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 41; 15) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 53, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 51; 16) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 63, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 61; 17) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 73, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 71; 18) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 83, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 81; 19) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 115; 20) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 107; 21) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 95; 22) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 99; 23) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 111; 24) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 103; 25) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 113; 26) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 105; 27) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 93; 28) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 97; 29) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 109; or 30) a light chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 91, and a heavy chain variable region comprising an amino acid sequence as set forth in SEQ ID NO: 101. 
     In another aspect, the present disclosure provides a fusion protein comprising the antibody or the antigen binding fragment or variant thereof according to the present disclosure. 
     In another aspect, the present disclosure provides isolated nucleic acid molecule or molecules, encoding for the antibody or the antigen binding fragment or variant thereof according to the present disclosure, or the fusion protein according to the present disclosure. 
     In another aspect, the present disclosure provides vector or vectors, comprising the isolated nucleic acid molecule or molecules according to the present disclosure. 
     In another aspect, the present disclosure provides a cell, comprising the isolated nucleic acid molecule or molecules or the vector or vectors according to the present disclosure. 
     In another aspect, the present disclosure provides a method for producing the antibody or the antigen binding fragment or variant thereof or the fusion protein according to the present disclosure, comprising culturing the cell according to the present disclosure under conditions enabling expression of said antibody or said antigen binding fragment or variant thereof, or said fusion protein. 
     In some embodiments, the method further comprises harvesting the antibody or the antigen binding fragment or variant thereof according to the present disclosure, or the fusion protein according to the present disclosure. 
     In another aspect, the present disclosure provides a composition, comprising the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure, and optionally a pharmaceutically acceptable excipient. 
     In another aspect, the present disclosure provides a use of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure in the manufacture of a medicament for preventing and/or treating cancer. 
     In another aspect, the present disclosure provides a use of the antibody or the antigen binding fragment or variant thereof, or the fusion protein according to the present disclosure in the manufacture of an agent for determining the presence and/or amount of CD27 in a sample. 
     In another aspect, the present disclosure provides a method for preventing and/or treating cancer in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In another aspect, the present disclosure provides a method for inducing or enhancing an immune response in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In some embodiments, the immune response is mediated by T cells. 
     In another aspect, the present disclosure provides a method for stimulating the proliferation of T cells, comprising administering to the T cells an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In another aspect, the present disclosure provides a method for activating a CD27 mediated signaling or for increasing an activity of the signaling in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In another aspect, the present disclosure provides a method for determining the presence and/or amount of CD27 in a sample, comprising: a) contacting the sample with the antibody or the antigen binding fragment or variant thereof, or the fusion protein according to the present disclosure; and b) determining the presence and/or amount of the antibody, the antigen binding fragment or variant thereof, or the fusion protein bound to the sample. 
     In another aspect, the present disclosure provides the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, or the cell according to the present disclosure, for a) preventing and/or treating cancer, b) inducing or enhancing an immune response, c) stimulating the proliferation of T cells, d) activating a CD27 mediated signaling or increasing an activity of the signaling, and/or e) determining the presence and/or amount of CD27 in a sample. 
     Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     INCORPORATION BY REFERENCE 
     All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the application are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present application will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the application are employed, and the accompanying drawings (also “figure” and “FIG.” herein), of which: 
         FIG. 1  illustrates binding of the anti-CD27 antibodies of the present disclosure to cell surface CD27, as detected by FACS. 
         FIG. 2  illustrates the specific binding of the anti-CD27 antibodies of the present disclosure to human CD27, as detected by FACS. 
         FIGS. 3A-3B  illustrate the activation activity of the anti-CD27 antibodies according to the present disclosure. 
         FIGS. 4A-4B  illustrate the activity of the anti-CD27 antibodies of the present disclosure to stimulate T cell proliferation. 
         FIGS. 5A-5B  illustrate binding of the anti-CD27 antibodies of the present disclosure to human CD27, as detected by ELISA. 
         FIG. 6  illustrates binding of the anti-CD27 antibodies of the present disclosure to CD27 on human cell surface, as detected by FACS. 
         FIG. 7  illustrates binding of the anti-CD27 antibodies of the present disclosure to CD27 on monkey cell surface, as detected by FACS. 
         FIG. 8  illustrates the activation activity of the anti-CD27 antibodies according to the present disclosure. 
         FIG. 9A  illustrates the activity of the anti-CD27 antibodies of the present disclosure to stimulate T cell proliferation. 
         FIG. 9B  illustrates the activity of the anti-CD27 antibodies of the present disclosure to stimulate the secretion of IFN-γ by T cells. 
         FIGS. 10A-10D  illustrate the stability of the anti-CD27 antibodies according to the present disclosure. 
         FIGS. 11A-11D  illustrate the stability of the anti-CD27 antibodies according to the present disclosure. 
         FIGS. 12A-12B  illustrate the expression of the recombinant CD27 protein by SDS-PAGE. 
         FIGS. 13A-13F  illustrate the expression of the anti-CD27 antibodies according to the present disclosure by SDS-PAGE. 
     
    
    
     DETAILED DESCRIPTION 
     While various embodiments of the application have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the application. It should be understood that various alternatives to the embodiments of the application described herein may be employed. 
     The term “antibody”, as used herein, generally refers to an immunoglobulin molecule usually composed of two identical pairs of polypeptide chains each having one “light” (L) chain and one “heavy” (H) chain. The light chains of an antibody can be classified as κ and λ light chains. The heavy chains can be classified as μ, δ, γ, α or ε, and the isotypes of an antibody are defined as IgM, IgD, IgG, IgA and IgE, respectively. Within the light and heavy chains, the variable and constant regions are joined by a “J” region of about 12 or more amino acids, and the heavy chains further comprise a “D” region of about 3 or more amino acids. Each heavy chain consists of a heavy chain variable region (VH) and a heavy chain constant region (CH). The heavy chain constant region consists of three domains (CH1, CH2 and CH3). Each light chain consists of a light chain variable region (VL) and a light chain constant region (CL). The light chain constant region consists of one domain, CL. The constant region of an antibody may mediate binding of the immunoglobulin to the host tissue or factor, including various cells of the immune system (e.g., effector cells) and the first component (Clq) of the classical complement system. The VH and VL regions can also be subdivided into regions with high variability known as complementarity determining regions (CDRs) interspersed with more conserved regions known as framework regions (FRs). Each VH and VL consists of 3 CDRs and 4 FRs arranged from N-terminal to C-terminal in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions (VH and VL) of each heavy/light chain pair form the antibody binding site, respectively. Distribution of amino acids to regions or domains follows the definition of Kabat Sequences of Proteins of Immunological Interest (National Institutes of Health, Bethesda, Md. (1987 and 1991)), or Chothia &amp; Lesk (1987) J. Mol. Biol. 196:901-917; Chothia et al. (1989) Nature 342:878-883. The amino acid positions described in the present invention are based on an online comparison of abysis tools (http://www.bioinf.org.uk/abysis/index.html) and do not represent actual positions in the amino acid sequence. The term “antibody” is not limited by any antibody-producing method. For example, it includes recombinant antibodies, monoclonal antibodies, and polyclonal antibodies. Antibodies may be antibodies of different isotypes, e.g., IgG (e.g., IgG1, IgG2, IgG3 or IgG4 subtype), IgA1, IgA2, IgD, IgE or IgM antibody. 
     The term “antigen binding fragment”, as used herein, generally refers to one or more fragments of a full-length antibody that retains the ability to bind the same antigen to which the antibody binds (e.g., CD27) and competes against an intact antibody for an antigen specific binding. Antigen binding fragment can be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. In some cases, the antigen binding site includes Fab, Fab″, F (ab′)2, F (ab)2, Fd, Fv, dAb and complementarity determining region (CDR) fragments, single chain antibodies (e.g., scFv), chimeric antibodies, diabodies, and polypeptides that comprise at least a portion of an antibody that is sufficient to confer specific antigen-binding ability to the polypeptide. 
     The term “variant”, as used herein, generally refers to a protein that differs from a parent molecule (e.g., polypeptide) by at least one amino acid. A variant may refer to the molecule itself, a composition comprising the molecule. It may also refer to the amino acid sequence of the molecule, when such a molecule is a polypeptide or protein. In some cases, a variant differs from its parent molecule (e.g., a protein) by an addition, deletion or substitution of one or more amino acid, such as 1-50, 1-40, 1-30, 1-20, 1-15, 1-14, 1-13, 1-12, 1-11, 1-10, 1-9, 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, or 1-2 amino acid. In some cases, the variant may possess at least about 80% (e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or higher) sequence homology with the amino acid sequence of its parent molecule. 
     The term “CD27”, as used herein, generally refers to the protein CD27 or a nucleic acid molecule encoding it. CD27 is a member of the tumor necrosis factor receptor superfamily. It binds to ligand CD70 and plays a key role in regulating B-cell activation and immunoglobulin synthesis. CD27 transduces signals that lead to the activation of NF-κB and MAPK8/JNK. 
     The term “binding specificity”, as used herein, generally refers to an ability of one substance to bind another substance specifically, and not easily to bind any other substance at random. For example, one protein may bind to another protein specifically due to their specific structures. For example, a targeting moiety may exhibit binding specificity to a corresponding tumor antigen. 
     The term “not substantially”, as used herein, generally refers to little or almost no binding to a particular substance. For example, very few or almost no (e.g., less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, less than 0.1%, or less than 0.01%) antibody, or the antigen binding fragment or variant thereof according to the present application binds to CD137, OX40 or GITR. 
     The term “CD137”, as used herein, generally refers to the protein CD137 or a nucleic acid molecule encoding it. CD137 is a member of the tumor necrosis factor (TNF) receptor family. CD137 is a co-stimulatory immune checkpoint molecule, and it is also known as 4-1BB, TNFRSF9 and ILA. CD137 can be expressed by activated T cells, in addition, dendritic cells, B cells, follicular dendritic cells, natural killer cells, granulocytes and cells of blood vessel walls at sites of inflammation may also express it. 
     The term “OX40”, as used herein, generally refers to the protein OX40 or a nucleic acid molecule encoding it. OX40 is also known as tumor necrosis factor receptor superfamily member 4 (TNFRSF4), or CD134. OX40 is a secondary co-stimulatory immune checkpoint molecule. OX40L binds to OX40 receptors on T-cells, preventing them from dying and subsequently increasing cytokine production. OX40 has a critical role in the maintenance of an immune response beyond the first few days and onwards to a memory response due to its ability to enhance survival. OX40 also plays a crucial role in both Th1 and Th2 mediated reactions in vivo. 
     The term “GITR”, as used herein, generally refers to glucocorticoid-induced TNFR-related protein, or tumor necrosis factor receptor superfamily member 18 (TNFRSF18). In humans, it is encoded by the TNFRSF18 gene. GITR is a co-stimulatory immune checkpoint molecule. It has been shown to be involved in inhibiting the suppressive activity of T-regulatory cells and extending the survival of T-effector cells. In mouse models, GITR was initially noted to be selectively enriched on the surface of regulatory T cells. 
     The term “K D ”, as used herein, generally refers to dissociation constant, a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules. The dissociation constant is the inverse of the association constant. In the specific case of antibodies (Ab) binding to antigen (Ag), usually the term affinity constant refers to the association constant. This chemical equilibrium is also the ratio of the on-rate (k forward ) and off-rate (k back ) constants. Two antibodies can have the same affinity, but one may have both a high on- and off-rate constant, while the other may have both a low on- and off-rate constant. 
     The term “CD27 mediated NF-κB activity”, as used herein, generally refers to noncanonical nuclear factor-κB (NF-κB) signaling pathway mediated by CD27, which mediates activation of the p52/RelB NF-κB complex and, thereby, regulates specific immunological processes. This NF-κB pathway relies on the inducible processing of NF-κB2 precursor protein, p100, as opposed to the degradation of IκBα in the canonical NF-κB pathway. A central signaling component of the noncanonical NF-κB pathway is NF-κB-inducing kinase (NIK), which functions together with a downstream kinase, inhibitor of NF-κB kinase α (IKKα), to induce phosphorylation-dependent ubiquitination and processing of p100. Under normal conditions, NIK is targeted for continuous degradation by a tumor necrosis factor (TNF) receptor-associated factor-3 (TRAF3)-dependent E3 ubiquitin ligase. In response to signals mediated by a subset of TNF receptor superfamily members, NIK becomes stabilized as a result of TRAF3 degradation, leading to the activation of noncanonical NF-κB. It is found that a specific subset of TNFR superfamily members mediates induction of noncanonical NF-κB signaling; these include LTβR, CD40, BAFFR, RANK, TNFR2, CD27, etc. 
     The term “T m ”, as used herein, generally refers to a midpoint value of a stability curve (melting temperature, also known as the temperature of hydrophobic exposure, T h ). It may be obtained by gradually increasing the temperature to unfold the protein and measuring the fluorescence at each point. The higher the T m , the more stable a protein is. 
     The term “dimerization”, as used herein, generally refers to the process of dimer formation. A dimer is an oligomer consisting of two monomers associated with each other by bonds that can be either covalent or non-covalent. When the two monomers are identical, the dimer is a homodimer; when the two monomers are not identical, the dimer is a heterodimer. 
     The term “monoclonal antibody”, as used herein, generally refers to antibodies that are made by identical immune cells that are all clones of a unique parent cell. Monoclonal antibodies can have monovalent affinity, in that they bind to the same epitope (the part of an antigen that is recognized by the antibody). It has become an important tool in biochemistry, molecular biology, and medicine. Several monoclonal antibody technologies had been developed recently, such as phage display, single B cell culture, single cell amplification from various B cell populations and single plasma cell interrogation technologies. 
     The term “chimeric antibody”, as used herein, generally refers to an antibody in which the Variable (V) region of light and heavy chains is of mouse origin, while the Constant (C) region is of human origin, so that nearly two-thirds of the entire antibody molecule is of human origin, which greatly reduces the immunogenicity degree of mouse-origin proteins compared to the original mouse monoclonal antibody. In general, the chimeric antibody retains the specificity and affinity of the original mouse monoclonal antibody, and HAMA response is also significantly reduced. 
     The term “humanized antibody”, as used herein, generally refers to antibodies from non-human species whose protein sequences have been modified to increase their similarity to antibody variants produced naturally in humans. Humanization can be necessary when the process of developing a specific antibody involves generation in a non-human immune system (such as that in mice). The protein sequences of antibodies produced in this way are partially distinct from homologous antibodies occurring naturally in humans and are therefore potentially immunogenic when administered to human patients. The protein sequence of a humanized antibody is essentially identical to that of a human variant, despite the non-human origin of some of its complementarity determining region (CDR) segments responsible for the ability of the antibody to bind to its target antigen. 
     The term “fully human antibody”, as used herein, generally refers to an antibody with fully human amino acid sequence derived antibody region therapeutics where antigen specificity has been selected either in vivo by the use of genetically modified mice or by antibody engineering processes combined with screening. Fully human and humanized antibodies carry a lower risk for inducing immune responses in humans than mouse or chimeric antibodies. 
     The term “bispecific antibody”, as used herein, generally refers to an artificial protein that can simultaneously bind to two different types of antigen. The main types of manufacturing methods are quadromas, chemical conjugation, and genetic recombination. IgG-like format retains the traditional monoclonal antibody (mAb) structure of two Fab arms and one Fc region, except the two Fab sites bind different antigens. Each heavy and light chain pair is from a unique mAb. The Fc region made from the two heavy chains forms the third binding site. Non-IgG-like format includes chemically linked Fabs, consisting of only the Fab regions, and various types of bivalent and trivalent single-chain variable fragments (scFvs). There are also fusion proteins mimicking the variable domains of two antibodies. Bispecific antibodies have a higher cytotoxic potential and bind to antigens that are expressed relatively weakly with a lower effective dose. Additionally, targeting more than one molecule can be useful to circumvent the regulation of parallel pathways and avoid resistance to the treatment. 
     The term “Fab fragment”, as used herein, generally refers to a portion (such as an antigen-binding fragment) of an immunoglobulin molecule. An Fab fragment may comprise one light chain and part of a heavy chain with a single antigen-binding site. A Fab fragment may be obtained by papain digestion of an immunoglobulin molecule. For example, a Fab fragment may be composed of one constant and one variable domain of each of the heavy and the light chain. The variable domain may contain the paratope (the antigen-binding site), comprising a set of complementarity determining regions, at the amino terminal end of the immunoglobulin molecule. The enzyme papain may be used to cleave an immunoglobulin molecule into two Fab fragments and one Fc fragment. The enzyme pepsin cleaves below the hinge region, so a F(ab′)2 fragment and a pFc′ fragment is formed. Divalent F(ab)2 or F(ab′)2 fragments have two antigen binding regions that are linked by disulfide bonds. Reduction of F(ab)2 or F(ab′)2 fragments produces 2 monovalent Fab or Fab′ fragments, which have a free sulfhydryl group that is useful for conjugation to other molecules. 
     The term “Fv fragment”, as used herein, generally refers to the smallest fragment made from enzymatic cleavage of IgG and IgM class antibodies. Fv fragments have the antigen-binding site made of the VH and VL regions, but they lack the CH1 and CL regions. The VH and VL chains are held together in Fv fragments by non-covalent interactions. 
     The term “ScFv”, as used herein, generally refers to a single-chain antibody fragment. An ScFv may refer to a recombinant single chain polypeptide molecule in which light and heavy chain variable regions of an antibody are connected by a peptide linker. Single chain antibodies (ScFv) generally do not include portions of the Fc region of antibodies that are involved in effector functions and are thus naked antibodies, although methods are known for adding such regions to known ScFv molecules if desired. See Helfrich et al., A rapid and versatile method for harnessing ScFv antibody fragments with various biological functions. J Immunol Methods 237: 131-145 (2000) and de Haard et al., Creating and engineering human antibodies for immunotherapy. Advanced Drug Delivery Reviews 31:5-31 (1998). 
     The term “IgG”, as used herein, generally refers to a subtype of an antibody. Each IgG has two antigen binding sites. Representing approximately 75% of serumantibodies in humans, IgG is the most common type of antibody found in the circulation. The recognized immunoglobulin genes include the κ, λ, α, γ (IgG1, IgG2, IgG3, IgG4). 
     The term “fusion protein”, as used herein, generally refers to a polypeptide that comprises, or alternatively consists of, an amino acid sequence of a polypeptide fused directly or indirectly (e.g., via a linker) to an amino acid sequence of a heterologous polypeptide (i.e., a polypeptide unrelated to the former polypeptide or the domain thereof). 
     The term “isolated nucleic acid molecule or molecules” as used herein, generally refers to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides, or analogs thereof, isolated from its native environment, or that is artificially synthesized. 
     The term “vector or vectors” as used herein, generally refers to a nucleic acid vehicle into which a polynucleotide encoding a protein can be inserted and expressed. The genetic material elements carried in the vector can be expressed in a host cell by transforming, transducing, or transfecting the host cell with the vector. Embodiments of vectors include: plasmids; phagemids; cosmos; artificial chromosomes such as yeast artificial chromosomes (YACs), bacterial artificial chromosomes (BACs) or P1-derived artificial chromosomes (PACs); phages such as λ phage or M13 phage and animal viruses. Animal virus used as a carrier include retrovirus (including lentivirus), adenovirus, adeno-associated virus, herpes virus (such as herpes simplex virus), jaundice virus, baculovirus, papilloma virus, papovaviruses (such as SV40). A vector may contain a variety of elements that control expression, including promoter sequences, transcriptional initiation sequences, enhancer sequences, selection elements, and reporter genes. In addition, the vector may also contain an origin of replication. It is also possible that the vector may include components that assist its entry into the cell, such as viral particles, liposomes or protein shells, but not only these substances. 
     The term “cell” as used herein, generally refers to a cell into which a vector is introduced and includes many cell types such as prokaryotic cells such as  Escherichia coli  and  Bacillus subtilis , fungal cells such as yeast cells or  Aspergillus  cells, insect cells such as S2  Drosophila  cells or Sf9, or animal cells such as fibroblasts, CHO cells, COS cells, NSO cells, HeLa cells, BHK cells, HEK293 cells or human cells. 
     The term “conditions enabling expression”, as used herein, generally refers to conditions enabling the expression of the antibody or the antigen binding fragment or variant thereof of the present application. In some embodiments, the conditions to enable expression include but not limited to incubation time, temperature, and culture medium, and may depend on cell type and may be readily determined by one of ordinary skill in the art. In some embodiments, during the process of producing the antibody or the antigen binding fragment or variant thereof of the present disclosure, the cells are grown in cultures, and in any apparatus that may be used to grow cultures, including fermenters. Cells may be grown as monolayers or attached to a surface. Alternatively, the cells may be grown in suspension. The cells can be grown in a culture medium that is serum-free. 
     The term “cancer” as used herein, generally refers to a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Cancer is fundamentally a disease of tissue growth regulation. In order for a normal cell to transform into a cancer cell, the genes that regulate cell growth and differentiation must be altered. The affected genes are divided into two broad categories. Oncogenes are genes that promote cell growth and reproduction. Tumor suppressor genes are genes that inhibit cell division and survival. Malignant transformation can occur through the formation of novel oncogenes, the inappropriate over-expression of normal oncogenes, or by the under-expression or disabling of tumor suppressor genes. Typically, changes in multiple genes are required to transform a normal cell into a cancer cell. Cancers are classified by the type of cell that include carcinoma, sarcoma, lymphoma and leukemia, germ cell tumor and blastoma. 
     The term “T cell” as used herein, generally refers to a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called T cells because they mature in the thymus from thymocytes. The majority of human T cells rearrange their alpha and beta chains on the cell receptor and are termed alpha beta T cells (αβ T cells) and are part of the adaptive immune system. Specialized gamma delta T cells, (a small minority of T cells in the human body, more frequent in ruminants), have invariant T-cell receptors with limited diversity, that can effectively present antigens to other T cells and are considered to be part of the innate immune system. 
     The term “pharmaceutically acceptable excipient”, as used herein, generally refers to any and all solvents, dispersion media, coatings, isotonic and absorption delaying agents, etc., that are compatible with pharmaceutical administration. 
     The term “about”, as used herein, generally refers to an approximation to a given value that would reasonably be inferred based on the ordinary skill in the art, including equivalents and approximations due to the experimental and/or measurement conditions for such given value. For example, it may refer to a value that is no more than 10% above or below the value being modified by the term. For example, the term “about 5 μg/kg” means a range of 4.5 μg/kg to 5.5 μg/kg. As another example, “about 1 hour” means a range of 48 minutes to 72 minutes. 
     The term “effective amount”, as used herein, generally refers to a dose sufficient to provide concentrations high enough to impart a beneficial effect on the recipient thereof. The specific therapeutically effective dose level for any particular subject will depend upon a variety of factors including the disorder being treated, the severity of the disorder, the activity of the specific component, the route of administration, the rate of clearance, the duration of treatment, the age, body weight, sex, diet, and general health of the subject, and other related factors. 
     The term “binding specificity” as used herein, generally refers to the ability to specifically bind (e.g., immunoreact with) a given target (while not binding or substantially not binding a non-target). An antibody (or its antigen binding fragment or variant) of the present disclosure may be monospecific and contain one or more binding sites which specifically bind a target or may be multispecific (e.g., bispecific or trispecific) and contain two or more binding sites which specifically bind the same or different targets. 
     The term “modification” as used herein, generally refers to any manipulation of the peptide backbone (e.g. amino acid sequence) or any post-translational modifications (e.g. glycosylation) of a polypeptide. For example, a modification is in comparison to the sequence of a corresponding wildtype polypeptide. A modification may be a substitution, an addition, and/or a deletion of one or more amino acids (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more). 
     The term “amino acid substitution” as used herein, generally refers to that one amino acid at a specific position of a polypeptide is replaced by another amino acid. 
     The term “EU index of the KABAT number” as used herein, generally refers to the index of the EU number corresponding to the amino acid sequence according to Kabat et al. (1971) Ann. NY Acad, Sci. 190:382-391 and Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, U.S. Department of Health and Human Services, NIH Publication No. 91-3242. 
     The term “isolated polynucleotide” as used herein, generally refers to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides, or analogs thereof, isolated from its native environment, or that is artificially synthesized. 
     CD27 Antibody, the Antigen Binding Fragment or Variant Thereof 
     In one aspect, the present disclosure provides an antibody, or an antigen binding fragment or variant thereof, which may bind to CD27. 
     The antibody, or the antigen binding fragment or variant thereof may specifically bind to CD27, and does not substantially bind to CD137, OX40 or GITR. For example, the antibody, or the antigen binding fragment or variant thereof may bind to CD27 with a percentage of at least 30% (for example, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% or more), as measured by FACS. In addition, the antibody, or the antigen binding fragment or variant thereof may bind to OX40 with a percentage of at most 5% (for example, at most 4.5%, at most 4%, at most 3.5%, at most 3%, at most 2.5%, at most 2%, at most 1.5%, at most 1%, at most 0.5%, or less), as measured by FACS. In addition, the antibody, or the antigen binding fragment or variant thereof may bind to CD137 with a percentage of at most 5% (for example, at most 4.5%, at most 4%, at most 3.5%, at most 3%, at most 2.5%, at most 2%, at most 1.5%, at most 1%, at most 0.5%, or less), as measured by FACS. In addition, the antibody, or the antigen binding fragment or variant thereof may bind to GITR with a percentage of at most 5% (for example, at most 4.5%, at most 4%, at most 3.5%, at most 3%, at most 2.5%, at most 2%, at most 1.5%, at most 1%, at most 0.5%, or less), as measured by FACS. 
     The antibody, or the antigen binding fragment or variant thereof may bind to CD27 with a K D  of 10 −7  M or less, e.g., with a K D  of 10 −8  M or less, of 9×10 −9  M or less, of 8×10 −9  M or less, of 7×10 −9  M or less, of 6×10 −9  M or less, of 5×10 −9  M or less, of 4×10 −9  M or less, of 3×10 −9  M or less, of 2×10 −9  M or less, of 1×10 −9  M or less, of 9×10 −10  M or less, of 8×10 −10  M or less, of 7×10 −10  M or less, of 5×10 −10  M or less, or of 1×10 −10  M or less. 
     The antibody, or the antigen binding fragment or variant thereof may activate and/or increase CD27 mediated NF-κB activity. For example, as shown in Luciferase Reporter Assay. 
     The antibody, or the antigen binding fragment or variant thereof may stimulate CD4 +  and/or CD8 +  T cell proliferation. For example, the proliferation rate of the CD4 +  and/or CD8 +  T cell may be enhanced by 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 100% or more, 150% or more, 200% or more, 250% or more, 300% or more, 350% or more, or 400% or more. 
     The antibody, or the antigen binding fragment or variant thereof may bind to human CD27 expressed on a cell surface. The antibody, or the antigen binding fragment or variant thereof may also bind to monkey CD27 expressed on a cell surface. 
     The antibody, or the antigen binding fragment or variant thereof may stimulate secretion of IFN-γ by CD4 +  and/or CD8 +  T cells. For example, the secretion of IFN-γ may be enhanced to at least 200 pg/mL, at least 400 pg/mL, at least 600 pg/mL, at least 800 pg/mL, at least 1000 pg/mL, at least 2000 pg/mL, at least 2500 pg/mL, at least 3000 pg/mL, at least 3500 pg/mL, or at least 4000 pg/mL or more. 
     The antibody, or the antigen binding fragment or variant thereof may have a T m  of at least 50° C. (for example, at least 55° C., at least 59° C., at least 60° C., at least 61° C., at least 62° C., at least 63° C., at least 64° C., at least 65° C., at least 66° C., at least 67° C., at least 68° C., at least 69° C., at least 70° C. or higher), for example as tested by DSC. 
     The antibody, or the antigen binding fragment or variant thereof may show a relative decrease of dimerization of less than about 10% (e.g., less than about 9%, less than about 8%, less than about 7%, less than about 6%, less than about 5.5%, less than about 5%, less than about 4%, less than about 3%, less than about 2%, less than about 1% or less) in SEC-HPLC analysis. For example, when dissolved in a PBS solution at a concentration of 5-15 mg/ml (for example, about 5-14 mg/ml, about 5-13 mg/ml, about 5-12 mg/ml, about 5-11 mg/ml, about 5-10 mg/ml, about 5-9 mg/ml, about 5-8 mg/ml, about 5-7 mg/ml, about 5-6 mg/ml). The pH may be about 6.5-about 8.5 (e.g., about 6.8-about 8.5, about 7.0-about 8.5, about 7.1-about 8.5, about 7.2-about 8.5, about 7.3-about 8.5, about 7.4-about 8.5, about 7.5-about 8.5, about 7.6-about 8.5, about 7.7-about 8.5, about 7.8-about 8.5, about 7.9-about 8.5, or about 8.0-about 8.5). May be under a temperature of about 30° C. to about 70° C. (e.g., about 35° C. to about 70° C., about 40° C. to about 70° C., about 41° C. to about 70° C., about 42° C. to about 70° C., about 43° C. to about 70° C., about 44° C. to about 70° C., about 45° C. to about 70° C., about 46° C. to about 70° C., about 47° C. to about 70° C., about 48° C. to about 70° C., about 49° C. to about 70° C., about 50° C. to about 70° C., about 55° C. to about 70° C., about 60° C. to about 70° C., or about 65° C. to about 70° C.). During a course of about 10-45 days (e.g., about 15-45 days, about 20-45 days, about 25-45 days, about 26-45 days, about 27-45 days, about 28-45 days, about 29-45 days, about 30-45 days, about 31-45 days, about 32-45 days, about 33-45 days, about 34-45 days, about 35-45 days, or about 40-45 days). 
     In the present disclosure, it is preferable for the antibody, or the antigen binding fragment or variant thereof to remain in the form of a dimer (e.g., instead of monomer, trimer or other multimers). 
     The antibody, or the antigen binding fragment or variant thereof may show a change of concentration of less than about 30% (e.g., less than about 25%, less than about 20%, less than about 19%, less than about 18%, less than about 17%, less than about 16%, less than about 15%, less than about 14%, less than about 13%, less than about 12%, less than about 11%, less than about 10%, less than about 9%, less than about 8%, less than about 7%, or less than about 5% or less) when dissolved in a solvent solution (e.g., a PBS solution). The antibody, or the antigen binding fragment or variant thereof may be dissolved at a concentration of about 5-15 mg/ml (e.g., about 6-15 mg/ml, about 7-15 mg/ml, about 8-15 mg/ml, about 9-15 mg/ml, about 10-15 mg/ml, about 11-15 mg/ml, about 12-15 mg/ml, about 13-15 mg/ml, or about 14-15 mg/ml, such as about 8-12 mg/ml, about 9-11 mg/ml, or about 9.5-10.5 mg/ml). The pH may be about 6.5-about 8.5 (e.g., about 6.8-about 8.5, about 7.0-about 8.5, about 7.1-about 8.5, about 7.2-about 8.5, about 7.3-about 8.5, about 7.4-about 8.5, about 7.5-about 8.5, about 7.6-about 8.5, about 7.7-about 8.5, about 7,8-about 8.5, about 7.9-about 8.5, or about 8.0-about 8.5). May be under a temperature of about 30° C. to about 70° C. (e.g., about 35° C. to about 70° C., about 40° C. to about 70° C., about 41° C. to about 70° C., about 42° C. to about 70° C., about 43° C. to about 70° C., about 44° C. to about 70° C., about 45° C. to about 70° C., about 46° C. to about 70° C., about 47° C. to about 70° C., about 48° C. to about 70° C., about 49° C. to about 70° C., about 50° C. to about 70° C., about 55° C. to about 70° C., about 60° C. to about 70° C., or about 65° C. to about 70° C.). During a course of about 10-45 days (e.g., about 15-45 days, about 20-45 days, about 25-45 days, about 26-45 days, about 27-45 days, about 28-45 days, about 29-45 days, about 30-45 days, about 31-45 days, about 32-45 days, about 33-45 days, about 34-45 days, about 35-45 days, or about 40-45 days). 
     The antibody according to the present disclosure may be selected from the group consisting of: a monoclonal antibody, a chimeric antibody, a humanized antibody, a fully human antibody and a bispecific antibody. 
     The antigen binding fragment according to the present disclosure may be selected from the group consisting of: a Fab fragment, a Fab′ fragment, a F(ab)2 fragment, a F(ab′)2 fragment, a Fv fragment, and an ScFv. 
     In some cases, the variant may be a polypeptide different from the antibody or antigen binding fragment thereof according to the present disclosure by an addition, deletion or substitution of one or more amino acid, such as 1-50, 1-40, 1-30, 1-20, 1-15, 1-14, 1-13, 1-12, 1-11, 1-10, 1-9, 1-8, 1-7, 1-6, 1-5, 1-4, 1-3, or 1-2 amino acids. 
     In some cases, the variant may be a polypeptide having a sequence identity of at least 80% (e.g., e.g., at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99% or higher) with the antibody or antigen binding fragment thereof according to the present disclosure. 
     In the present disclosure, the antibody or the antigen binding fragment or variant thereof may compete with a reference antibody for binding to CD27. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 8, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 9, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 10, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 5, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 6, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 7. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 18, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 19, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 20, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 15, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 16, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 17. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 28, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 29, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 30, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 25, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 26, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 27. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 38, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 39, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 40, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 35, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 36, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 37. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 48, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 49, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 50, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 45, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 46, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 47. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 58, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 59, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 60, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 55, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 56, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 57. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 68, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 69, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 70, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 65, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 66, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 67. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 78, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 79, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 80, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 75, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 76, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 77. 
     In some cases, the reference antibody comprises light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 88, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 89, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 90, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 85, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 86, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 87. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 3, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 1. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 13, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 11. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 23, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 21. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 33, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 31. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 43, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 41. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 53, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 51. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 63, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 61. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 73, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 71. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 83, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 81. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 115. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 107. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 95. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 99. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 111. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 103. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 113. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 105. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 93. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 97. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 109. 
     In some cases, the reference antibody comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 101. 
     In the present disclosure, the antibody, or the antigen binding fragment or variant thereof may comprise an antibody light chain or a fragment thereof. 
     For example, the antibody light chain or fragment thereof may comprise LCDR1, and the LCDR1 may comprise an amino acid sequence selected from SEQ ID NO: 8, 18, 28, 38, 48, 58, 68, 78 and 88. The antibody light chain or fragment thereof may comprise LCDR2, and the LCDR2 may comprise an amino acid sequence selected from SEQ ID NO: 9, 19, 29, 39, 49, 59, 69, 79 and 89. The antibody light chain or fragment thereof may comprise LCDR3, and the LCDR3 may comprise an amino acid sequence selected from SEQ ID NO: 10, 20, 30, 40, 50, 60, 70, 80 and 90. 
     Further, the antibody light chain or fragment thereof may comprise a light chain variable region VL, and the light chain variable region VL may comprise an amino acid sequence selected from SEQ ID NO: 3, 13, 23, 33, 43, 53, 63, 73, 83 and 91. 
     The antibody light chain or the fragment thereof may also comprise a constant region. The light chain constant region may comprise an Igκ constant region, for example, a human Igκ constant region. 
     In some embodiments, the light chain or the fragment thereof comprises an amino acid sequence selected from SEQ ID NO: 117, 119, 121, 123, 125, 127, 129, 131 and 133. 
     In the present disclosure, the antibody, or the antigen binding fragment or variant thereof may comprise an antibody heavy chain or a fragment thereof. 
     For example, the antibody heavy chain or the fragment thereof may comprise HCDR1, and the HCDR1 may comprise an amino acid sequence selected from SEQ ID NO: 5, 15, 25, 35, 45, 55, 65, 75 and 85. The antibody heavy chain or the fragment thereof may comprise HCDR2, and the HCDR2 may comprise an amino acid sequence selected from SEQ ID NO: 6, 16, 26, 36, 46, 56, 66, 76 and 86. The antibody heavy chain or the fragment thereof may comprise HCDR3, and the HCDR3 may comprise an amino acid sequence selected from SEQ ID NO: 7, 17, 27, 37, 47, 57, 67, 77 and 87. 
     Further, the antibody heavy chain or the fragment thereof may comprise a heavy chain variable region VH, and the heavy chain variable region VH may comprise an amino acid sequence selected from SEQ ID NO: 1, 11, 21, 31, 41, 51, 61, 71, 81, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113 and 115. 
     The antibody heavy chain or the fragment thereof may also comprise a human constant region. For example, the human constant region may comprise a constant region of human IgG. For example, the IgG constant region may comprise the constant region of human IgG1. 
     In some embodiments, the heavy chain or the fragment thereof comprises an amino acid sequence selected from SEQ ID NO: 118, 120, 122, 124, 126, 128, 130, 132 and 134. 
     In the present disclosure, the CD27 may be selected from the group consisting of: a human CD27, a mouse CD27 and a monkey CD27. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 8, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 9, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 10, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 5, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 6, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 7. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 18, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 19, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 20, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 15, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 16, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 17. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 28, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 29, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 30, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 25, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 26, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 27. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 38, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 39, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 40, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 35, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 36, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 37. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 48, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 49, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 50, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 45, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 46, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 47. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 58, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 59, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 60, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 55, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 56, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 57. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 68, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 69, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 70, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 65, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 66, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 67. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 78, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 79, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 80, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 75, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 76, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 77. 
     In the present disclosure, the antibody or the antigen binding fragment thereof may comprise light chain CDR1-3 and heavy chain CDR1-3, the light chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 88, the light chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 89, the light chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 90, the heavy chain CDR1 may comprise an amino acid sequence as set forth in SEQ ID NO: 85, the heavy chain CDR2 may comprise an amino acid sequence as set forth in SEQ ID NO: 86, and the heavy chain CDR3 may comprise an amino acid sequence as set forth in SEQ ID NO: 87. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 3, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 1. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 13, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 11. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 23, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 21. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 33, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 31. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 43, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 41. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 53, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 51. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 63, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 61. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 73, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 71. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 83, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 81. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 115. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 107. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 95. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 99. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 111. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 103. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 113. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 105. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 93. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 97. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 109. 
     In some cases, the antibody or the antigen binding fragment thereof comprises a light chain variable region and a heavy chain variable region, the light chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 91, and the heavy chain variable region may comprise an amino acid sequence as set forth in SEQ ID NO: 101. 
     For example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m2E7. The LCDR1-3 of the antibody m2E7 are as set forth in SEQ ID NO: 28-30, respectively, and the HCDR1-3 of the antibody m2E7 are as set forth in SEQ ID NO: 25-27, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m2B8. The LCDR1-3 of the antibody m2B8 are as set forth in SEQ ID NO: 18-20, respectively, and the HCDR1-3 of the antibody m2B8 are as set forth in SEQ ID NO: 15-17, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m4H3. The LCDR1-3 of the antibody m4H3 are as set forth in SEQ ID NO: 68-70, respectively, and the HCDR1-3 of the antibody m4H3 are as set forth in SEQ ID NO: 65-67, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m3E7. The LCDR1-3 of the antibody m3E7 are as set forth in SEQ ID NO: 38-40, respectively, and the HCDR1-3 of the antibody m3E7 are as set forth in SEQ ID NO: 35-37, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m1A8. The LCDR1-3 of the antibody m1A8 are as set forth in SEQ ID NO: 8-10, respectively, and the HCDR1-3 of the antibody m1A8 are as set forth in SEQ ID NO: 5-7, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m4G1. The LCDR1-3 of the antibody m4G1 are as set forth in SEQ ID NO: 58-60, respectively, and the HCDR1-3 of the antibody m4G1 are as set forth in SEQ ID NO: 55-57, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m2G3. The LCDR1-3 of the antibody m2G3 are as set forth in SEQ ID NO: 78-80, respectively, and the HCDR1-3 of the antibody m2G3 are as set forth in SEQ ID NO: 75-77, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m2F11. The LCDR1-3 of the antibody m2F11 are as set forth in SEQ ID NO: 88-90, respectively, and the HCDR1-3 of the antibody m2F11 are as set forth in SEQ ID NO: 85-87, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise LCDR1-3 and HCDR1-3 that are the same as those of the antibody m3B8. The LCDR1-3 of the antibody m3B8 are as set forth in SEQ ID NO: 48-50, respectively, and the HCDR1-3 of the antibody m3B8 are as set forth in SEQ ID NO: 45-47, respectively. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m2E7. The light chain variable region of the antibody m2E7 is as set forth in SEQ ID NO: 21, and the heavy chain variable region of the antibody m2E7 is as set forth in SEQ ID NO: 23. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d16647. The light chain variable region of the antibody d16647 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d16647 is as set forth in SEQ ID NO: 115. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d12996. The light chain variable region of the antibody d12996 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d12996 is as set forth in SEQ ID NO: 107. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d9419. The light chain variable region of the antibody d9419 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d9419 is as set forth in SEQ ID NO: 95. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d9424. The light chain variable region of the antibody d9424 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d9424 is as set forth in SEQ ID NO: 99. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d14822. The light chain variable region of the antibody d14822 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d14822 is as set forth in SEQ ID NO: 111. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody d12674. The light chain variable region of the antibody d12674 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody d12674 is as set forth in SEQ ID NO: 103. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 16647. The light chain variable region of the antibody 16647 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 16647 is as set forth in SEQ ID NO: 113. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 12996. The light chain variable region of the antibody 12996 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 12996 is as set forth in SEQ ID NO: 105. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 9419. The light chain variable region of the antibody 9419 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 9419 is as set forth in SEQ ID NO: 93. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 9424. The light chain variable region of the antibody 9424 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 9424 is as set forth in SEQ ID NO: 97. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 14822. The light chain variable region of the antibody 14822 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 14822 is as set forth in SEQ ID NO: 109. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody 12674. The light chain variable region of the antibody 12674 is as set forth in SEQ ID NO: 91, and the heavy chain variable region of the antibody 12674 is as set forth in SEQ ID NO: 101. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m2B8. The light chain variable region of the antibody m2B8 is as set forth in SEQ ID NO: 13, and the heavy chain variable region of the antibody m2B8 is as set forth in SEQ ID NO: 11. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m4H3. The light chain variable region of the antibody m4H3 is as set forth in SEQ ID NO: 63, and the heavy chain variable region of the antibody m4H3 is as set forth in SEQ ID NO: 61. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m3E7. The light chain variable region of the antibody m3E7 is as set forth in SEQ ID NO: 33, and the heavy chain variable region of the antibody m3E7 is as set forth in SEQ ID NO: 31. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m1A8. The light chain variable region of the antibody m1A8 is as set forth in SEQ ID NO: 3, and the heavy chain variable region of the antibody m1A8 is as set forth in SEQ ID NO: 1. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m4G1. The light chain variable region of the antibody m4G1 is as set forth in SEQ ID NO: 53, and the heavy chain variable region of the antibody m4G1 is as set forth in SEQ ID NO: 51. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m2G3. The light chain variable region of the antibody m2G3 is as set forth in SEQ ID NO: 73, and the heavy chain variable region of the antibody m2G3 is as set forth in SEQ ID NO: 71. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m2F11. The light chain variable region of the antibody m2F11 is as set forth in SEQ ID NO: 83, and the heavy chain variable region of the antibody m2F11 is as set forth in SEQ ID NO: 81. 
     As another example, the antibody or the antigen binding fragment thereof may comprise a light chain variable region and a heavy chain variable region that are the same as those of the antibody m3B8. The light chain variable region of the antibody m3B8 is as set forth in SEQ ID NO: 43, and the heavy chain variable region of the antibody m3B8 is as set forth in SEQ ID NO: 41. 
     In some embodiments, the antibody according to the present disclosure is selected from the group consisting of: m2E7, m2B8, m4H3, m3E7, m1A8, m4G1, m2G3, m2F11, m3B8, d16647, d12996, d9419, d9424, d14822, d12674, 16647, 12996, 9419, 9424, 14822, 12674. 
     In another aspect, the present disclosure provides a fusion protein. The fusion protein may comprise the antibody, or the antigen binding fragment or variant thereof according to the present disclosure. 
     For example, the fusion protein may comprise one or more additional components, such as other pharmaceutical active components. The additional component may be fused to the antibody, or its antigen binding fragment or variant according to the present disclosure directly or indirectly (e.g., via a linker, such as a peptide linker). The fusion protein may still have at least some of the properties of the antibody, or its antigen binding fragment or variant according to the present disclosure. 
     Nucleic Acid, Vector, Cell and the Method of Preparation 
     In another aspect, the present disclosure provides isolated nucleic acid or isolated nucleic acids, encoding for the antibody, the antigen binding fragment or variant thereof, or the fusion protein according to the present disclosure. 
     The isolated nucleic acids may comprise one or more nucleic acid molecules, with each encoding the antibody of the present disclosure, an antigen binding fragment thereof, or a variant thereof. For example, the isolated nucleic acids may comprise at least two nucleic acid molecules, with one encoding the antibody heavy chain or a fragment/variant thereof, and one encoding the antibody light chain or a fragment/variant thereof. In some cases, the isolated nucleic acids may encode for a fusion protein. 
     The isolated nucleic acid or isolated nucleic acids may be synthesized using recombinant techniques well known in the art. For example, the isolated nucleic acid or isolated nucleic acids may be synthesized with an automated DNA synthesizer. 
     Standard recombinant DNA and molecular cloning techniques include those described by Sambrook, Fritsch, E. F. and Maniatis, T.  Molecular Cloning: A Laboratory Manual ; Cold Spring Harbor Laboratory Press: Cold Spring Harbor, (1989) (Maniatis) and by T. J. Silhavy, M. L. Bennan, and L. W. Enquist,  Experiments with Gene Fusions , Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (1984) and by Ausubel, F. M et al.,  Current Protocols in Molecular Biology , pub. by Greene Publishing Assoc. and Wiley-Interscience (1987). Briefly, the subject nucleic acids may be prepared from genomic DNA fragments, cDNAs, and RNAs, all of which may be extracted directly from a cell or recombinantly produced by various amplification processes including but not limited to PCR and RT-PCR. 
     Direct chemical synthesis of nucleic acids typically involves sequential addition of 3′-blocked and 5′-blocked nucleotide monomers to the terminal 5′-hydroxyl group of a growing nucleotide polymer chain, wherein each addition is effected by nucleophilic attack of the terminal 5′-hydroxyl group of the growing chain on the 3′-position of the added monomer, which is typically a phosphorus derivative, such as a phosphotriester, phosphoramidite, or the like. See for example, Matteuci et al.,  Tet. Lett.  521:719 (1980); U.S. Pat. No. 4,500,707 to Caruthers et al.; and U.S. Pat. Nos. 5,436,327 and 5,700,637 to Southern et al. 
     In another aspect, the present disclosure provides a vector or vectors, comprising the isolated nucleic acid molecule or molecules. 
     The vector may be any linear nucleic acids, plasmids, phagemids, cosmids, RNA vectors, viral vectors and the like. Non-limiting examples of a viral vector may include a retrovirus, an adenovirus and an adeno-associated virus. In some embodiments, the vector is an expression vector, e.g. a phage display vector. 
     An expression vector may be suitable for use in particular types of host cells and not others. For example, the expression vector can be introduced into the host organism, which is then monitored for viability and expression of any genes/polynucleotides contained in the vector. 
     The expression vector may also contain one or more selectable marker genes that, upon expression, confer one or more phenotypic traits useful for selecting or otherwise identifying host cells that carry the expression vector. Non-limiting examples of suitable selectable markers for eukaryotic cells include dihydrofolate reductase and neomycin resistance. 
     The subject vectors can be introduced into a host cell stably or transiently by a variety of established techniques. For example, one method involves a calcium chloride treatment wherein the expression vector is introduced via a calcium precipitate. Other salts, for example calcium phosphate, may also be used following a similar procedure. In addition, electroporation (that is, the application of current to increase the permeability of cells to nucleic acids) may be used. Other examples of transformation methods include microinjection, DEAE dextran mediated transformation, and heat shock in the presence of lithium acetate. Lipid complexes, liposomes, and dendrimers may also be employed to transfect the host cells. 
     In another aspect, the present disclosure provides a cell (e.g., an isolated cell, such as a host cell), comprising the isolated nucleic acid molecule or molecules of the present disclosure or the vector or vectors of the present disclosure. 
     The cell may express the antibody, or the antigen binding fragment or variant thereof of the present disclosure, or the fusion protein of the present disclosure. The cell may be a eukaryotic cell or a prokaryotic cell. An appropriate cell may be transformed or transfected with the nucleic acid(s) or vector(s) of the present disclosure and utilized for the expression and/or secretion of the antibody, the antigen binding fragment or variant thereof, or the fusion protein. For example, the cell may be  E. coli  cells, other bacterial host cells, yeast cells, or various higher eukaryotic cells. 
     In another aspect, the present disclosure provides a method for producing the antibody, the antigen binding fragment or variant thereof, or the fusion protein of the present disclosure, comprising culturing the cell of the present disclosure under conditions enabling expression of the antibody, the antigen binding fragment or variant thereof, or the fusion protein. 
     The method may further comprise harvesting the antibody, the antigen binding fragment or variant thereof, or the fusion protein of the present disclosure. 
     Pharmaceutical Compositions 
     In another aspect, the present disclosure provides a composition, comprising the antibody, the antigen binding fragment or variant thereof, the vector or vectors, the fusion protein, and/or the isolated nucleic acid molecule or molecules according to the present disclosure, and optionally a pharmaceutically acceptable excipient. 
     In some embodiments, the pharmaceutical composition further comprises an effective amount of an additional therapeutically active component for cancer treatment. For example, the additional therapeutically active component for cancer treatment may be an agent for chemotherapy. In some embodiments, the agent for chemotherapy is a cytotoxic agent. Each of the active components may be present in the pharmaceutical composition in a pharmaceutically active amount. 
     Described below are non-limiting exemplary pharmaceutical compositions and methods for preparing the same. The pharmaceutical composition may, for example, be in a form suitable for oral administration as a tablet, capsule, pill, powder, sustained release formulations, solution, suspension, for parenteral injection as a sterile solution, suspension or emulsion, for topical administration as an ointment or cream or for rectal administration as a suppository. The pharmaceutical composition may be in unit dosage forms suitable for single administration of precise dosages. In some embodiments, the pharmaceutical composition may be a liquid pharmaceutical composition suitable for oral consumption. 
     Pharmaceutical compositions of the disclosure suitable for oral administration can be presented as discrete dosage forms, such as capsules, cachets, or tablets, or liquids or aerosol sprays each containing a predetermined amount of an active ingredient as a powder or in granules, a solution, or a suspension in an aqueous or non-aqueous liquid, an oil-in-water emulsion, or a water-in-oil liquid emulsion. Such dosage forms can be prepared by any of the methods of pharmacy, but all methods typically include the step of bringing the active ingredient into association with the carrier, which constitutes one or more other ingredients. In general, the compositions are prepared by uniformly and intimately mixing the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired presentation. 
     The antibody, the antigen binding fragment or variant thereof, or the fusion protein of the present disclosure can be combined in an intimate admixture with a pharmaceutical carrier according to conventional pharmaceutical compounding techniques. The carrier can take a wide variety of forms depending on the form of preparation desired for administration. In preparing the compositions for an oral dosage form, any of the usual pharmaceutical media can be employed as carriers, such as, for example, water, glycols, oils, alcohols, flavoring agents, preservatives, coloring agents, and the like in the case of oral liquid preparations (such as suspensions, solutions, and elixirs) or aerosols; or carriers such as starches, sugars, micro-crystalline cellulose, diluents, granulating agents, lubricants, binders, and disintegrating agents can be used in the case of oral solid preparations, in some embodiments without employing the use of lactose. For example, suitable carriers include powders, capsules, and tablets, with the solid oral preparations. If desired, tablets can be coated by standard aqueous or nonaqueous techniques. 
     The composition can further include one or more pharmaceutically acceptable additives and excipients. Such additives and excipients include, without limitation, detackifiers, anti-foaming agents, buffering agents, polymers, antioxidants, preservatives, chelating agents, viscomodulators, tonicifiers, flavorants, colorants, odorants, opacifiers, suspending agents, binders, fillers, plasticizers, lubricants, and mixtures thereof. 
     The pharmaceutical compositions of the present disclosure may comprise a therapeutically effective amount of the active agent (e.g., the antibody, the antigen binding fragment or variant thereof, or the fusion protein of the present disclosure). A therapeutically effective amount is an amount of the subject pharmaceutical composition capable of preventing and/or curing (at least partially) a condition or disorder (e.g., cancer) and/or any complications thereof in a subject suffering from or having a risk of developing said condition or disorder. The specific amount/concentration of the active agent comprised may vary according to the method of administration and the need of a patient, and can be determined based on e.g., volume, viscosity, and/or body weight of a patient etc. For example, an appropriate dosage may be about 0.1 mg or 1 mg/kg/day to about 50 mg/kg/day; sometimes, the dosage can be even higher. In some embodiments, the dosage applied may be from about 3 mg/kg/day to about 3.5 mg/kg/day, from 3.5 mg/kg/day to about 7.2 mg/kg/day, from about 7.2 mg/kg/day to about 11.0 mg/kg/day, from about 11.0 mg/kg/day to about 15.0 mg/kg/day. In some embodiments, the dosage applied is from about 10 mg/kg/day to about 50 mg/kg/day, for example, from about 20 mg to about 50 mg per day, administered twice/day. It shall be understood that these specific doses may be conveniently adjusted by a skilled person in the art (e.g., a doctor or a pharmacist) based on conditions of a specific patient, formulation, and/or disease. 
     Medical Use and Methods of Treatment 
     In another aspect, the present disclosure provides a use of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors and/or the cell according to the present disclosure in the manufacture of a medicament for preventing and/or treating cancer. 
     For example, the cancer may comprise tumor cells with elevated expression of CD27. For example, the cancer may be a hematologic tumor (such as CD27 +  lymphomas) or a solid tumor. For example, the cancer may be selected from the group consisting of: renal cell carcinoma, thymic cancer, nasopharyngeal carcinoma, Hodgkin and non-Hodgkin&#39;s lymphoma, Waldenstoom giant globulinemia, chronic lymphocytic leukemia, T-cell leukemia, multiple myeloma, EBV related and HTLV-1 related malignancies, pancreatic, laryngocarcinoma, pharynx, melanoma, ovarian cancer, lung cancer (including lung adenocarcinoma), colon cancer, breast cancer and brain cancer. 
     In another aspect, the present disclosure provides a use of the antibody or the antigen binding fragment or variant thereof, or the fusion protein according to the present disclosure in the manufacture of an agent for determining the presence and/or amount of CD27 in a sample. 
     In another aspect, the present disclosure provides a method for preventing and/or treating cancer in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In another aspect, the present disclosure provides a method for inducing or enhancing an immune response in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. For example, the immune response may be mediated by T cells. 
     In another aspect, the present disclosure provides a method for stimulating the proliferation of T cells, comprising administering to the T cells an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. The method may be an in vitro method. 
     In another aspect, the present disclosure provides a method for activating a CD27 mediated signaling or for increasing an activity of the signaling in a subject in need thereof, comprising administering to the subject an effective amount of the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, and/or the cell according to the present disclosure. 
     In another aspect, the present disclosure provides a method for determining the presence and/or amount of CD27 in a sample, comprising: a) contacting the sample with the antibody or the antigen binding fragment or variant thereof, or the fusion protein according to the present disclosure; and b) determining the presence and/or amount of the antibody, the antigen binding fragment or variant thereof, or the fusion protein bound to the sample. 
     In another aspect, the present disclosure provides the antibody or the antigen binding fragment or variant thereof, the fusion protein, the isolated nucleic acid molecule or molecules, the vector or vectors, or the cell according to the present disclosure, for a) preventing and/or treating cancer, b) inducing or enhancing an immune response, c) stimulating the proliferation of T cells, d) activating a CD27 mediated signaling or increasing an activity of the signaling, and/or e) determining the presence and/or amount of CD27 in a sample. 
     While preferred embodiments of the present disclosure have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the disclosure. It should be understood that various alternatives to the embodiments of the disclosure described herein may be employed in practicing the disclosure. It is intended that the following claims define the scope of the disclosure and that methods and structures within the scope of these claims and their equivalents be covered thereby. 
     EXAMPLES 
     The following examples are set 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 application, and are not intended to limit the scope of what the applicants regard as their application nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric. Standard abbreviations may be used, e.g., bp, base pair(s); kb, kilobase(s); pl, picoliter(s); s or sec, second(s); min, minute(s); h or hr, hour(s); aa, amino acid(s); nt, nucleotide(s); i.m., intramuscular(ly); i.p., intraperitoneal(ly); s.c., subcutaneous(ly); and the like. 
     Example 1 Expression of Recombinant Human CD27 Protein and Preparation of Related EGFP Cells 
     According to the protein database Uniprot, the amino acid sequence of the extracellular domain of human CD27 (i.e., residues 1 to 192 of P26842) was obtained according to the amino acid sequence of the human CD27 (hCD27, and the accession number in Uniprot is P26842). The amino acid sequence of the extracellular domain of the monkey CD27 (i.e., residues 1 to 192 of F7BYS2) was obtained according to the amino acid sequence of monkey CD27 (RhCD27, and the accession number in Uniprot is F7BYS2). The amino acid sequence of the human IgG1-Fc domain (Fc) (i.e., residues 104 to 330 of P01857) was obtained according to the amino acid sequence of the human immunoglobulin gamma1 (hIgG1, and the accession number in Uniprot is P01857). The amino acid sequence of the mouse IgG1-Fc (muFc) was obtained (i.e., residues 98 to 324 of P01868) was obtained according to the amino acid sequence of mouse immunoglobulin gamma1 (mIgG1, and the accession number in Uniprot is P01868). The corresponding coding DNA sequences were designed with the online tool DNAworks (http://helixweb.nih.gov/dnaworks/), thereby obtaining the corresponding coding sequences for the fusion proteins hCD27-Fc, hCD27-muFc and RhCD27-muFc. 
     The amino acid sequence of green fluorescence protein EGFP (the accession number is C5MKY7), human CD137 (hCD137, the accession number is Q07011), human OX40 (hOX40, the accession number is P43489), human GITR (hGITR, the accession number is Q9Y5U5), human CD27 (hCD27, the accession number is P26842), murine CD27 (mCD27, the accession number is P41272), and monkey CD27 (RhCD27, the accession number is F7BYS2) were obtained from the Uniprot database. Their corresponding coding DNA sequences were designed with the online tool DNAworks (http://helixweb.nih.gov/dnaworks/), thereby obtaining DNA sequences coding for the following EGFP-fusion proteins, respectively: hCD137-EGFP, hOX40-EGFP, hCD27-EGFP, hGITR-EGFP, mCD27-EGFP, and RhCD27-EGFP. 
     The synthesized DNA sequences were sub-cloned into the commercially available vector pcDNA4/myc-HisA (Invitrogen, V863-20), after being digested with Fermentas&#39; HindIII and PmeI enzymes. The plasmids were verified by sequencing and the following recombinant plasmids were obtained: pcDNA4-hCD27-hFc, pcDNA4-hCD27-muFc, pcDNA4-RhCD27-muFc, pcDNA4-hOX40-EGFP, pcDNA4-hCD137-EGFP, pcDNA4-mCD27-EGFP, pcDNA4-hCD27-EGFP, pcDNA4-hGITR-EGFP, pcDNA4-mCD27-EGFP and pcDNA4-RhCD27-EGFP. 
     Then, the recombinant plasmids were introduced into HEK293 (ATCC, CRL-1573™) cells by transfection, the expression of hOX40, hCD137, hGITR, hCD27, mCD27, and RhCD27 was confirmed 48 hours after transfection by fluorescence activated signal sorting (FACS). 
     The plasmids pcDNA4-hCD27-Fc, pcDNA4-hCD27-muFc and pcDNA4-RhCD27-muFc were transiently introduced into HEK293 cells by transfection, and the corresponding proteins were produced. Briefly, these plasmids were diluted with Freestyle 293 medium and appropriate PEI (polyethyleneimine) solution was added. Then, each plasmid/PEI mixture was added into the cell suspension, and incubated under 37° C., 10% CO 2  and 90 rpm. After 5-6 days, the culture supernatant was collected and preliminarily purified by ProteinA affinity chromatography to obtain hCD27-Fc, hCD27-muFc and RhCD27-muFc protein samples. The obtained protein samples were analyzed with SDS-PAGE ( FIGS. 12A-12B ) and expression of the desired target proteins was confirmed. 
       FIGS. 12A-12B  showed that CD27-Fc, CD27-muFc, RhCD27-muFc was successfully expressed and purified. In  FIG. 12A , lane 1 was loaded with CD27-Fc (original sample); lane 2 was loaded with CD27-Fc (flow-through); lane 3 was loaded with CD27-Fc (eluted); lane 4 was loaded with marker (26630); lane 5 was loaded with CD27-muFc (eluted); lane 6 was loaded with CD27-muFc (original sample); lane 7 was loaded with CD27-muFc (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was empty; lane 10 was loaded with CD27-Fc (eluted, non-reducing); and lane 11 was loaded with CD27-Fc (eluted, non-reducing). 
     In  FIG. 12B , lane 1 was loaded with marker (26619); lane 2 was loaded with RhCD27-muFc (eluted); lane 3 was loaded with RhCD27-muFc (original sample); lane 4 was loaded with RhCD27-muFc (flow-through); lane 5 was loaded with 1 μg Std; lane 6 was blank; lane 7 was empty; lane 8 was loaded with RhCD27-muFc (eluted, non-reducing). 
     Example 2 Anti-CD27 Antibody Obtained from Hybridoma 
     Mice were immunized with the hCD27-muFc protein prepared as described in Example 1 and antibody titer was determined after three immunizations. The mice showing a high titer were selected for the fourth immunization. Spleen cells were isolated from the mice after the fourth immunization, and the spleen cells were fused with mouse myeloma cells SP2/0. The supernatant obtained from the fused cells was subjected to ELISA binding test, and a total of 400 hybridoma clones capable of binding to CD27 were obtained. 
     Briefly, the ELISA plate was coated with 2 μg/ml CD27-Fc, 100 μl/well and incubated overnight under 4° C. Then, it was washed once with 10 mM, pH 7.4 PBS/Tween (0.05%), and was blocked with PBST containing 5% skimmed milk powder, incubated at 37° C. for 2 h. After washing the plate for 4 times, the hybridoma supernatant was added and it was incubated at 37° C. for 40 min. The plate was then washed for 4 times, and anti-mouse IgG-HRP-conjugated secondary antibody (Abcam, Cat #ab97040) was added and incubated at 37° C. for 40 min. After washing, the signal was developed with TMB substrate and spectrophotometric analysis was performed at OD 450 . Clones with an OD of above 0.5 were considered positive. 
     The binding activities and activation abilities of the selected positive clones were examined by FACS, and the antibodies showing an activation activity were selected for further study. The FACS analysis was performed according to instructions. Briefly, 5×10 5  CD27-EGFP cells prepared in Example 1 were washed twice in PBS, 50 μl hybridoma supernatant as well as 50 μl PBS were added and incubated at 4° C. for 30 min. Then they were washed twice in PBS, and anti-mouse Ig-PE (eBioscience, Cat #2-4010-8) was added and incubated at 4° C. for 30 min, washed twice with PBS, resuspended in 300 μl PBS, and examined with flow cytometry. A total of 300 positive clones were obtained. 
     50 clones with strong binding affinity were selected for activation assay. The activation assay was performed as follows: 293T-CD27-NF-κB cells were digested with trypsin, after 2-3 mins, DMEM complete medium was added. The cells were gently suspended and transferred to 96-well plates, 100 μl/well. Supernatants from the 50 selected clones were mixed with anti-mouse crosslinking antibody (Jackson ImmunoResearch Laboratories: 115-006-008) and added to a 96-well plate. Complete medium was added to the control group. The cells were lysed after 30 hours and then tested using the luciferase assay system (Promega: E1501). Nine antibodies were selected, sub-cloned, and the clones obtained were sequenced. These nine antibodies were 2E7, 2B8, 4H3, 3E7, 1A8, 4G1, 2G3, 2F11 and 3B8. 
     After sequencing, the amino acid sequences of the 9 selected antibodies were determined as follows: the amino acid sequence of VL of clone 2E7 is as set forth in SEQ ID NO: 23, the amino acid sequence of VH of clone 2E7 is as set forth in SEQ ID NO: 21. The amino acid sequence of VL of clone 2B8 is as set forth in SEQ ID NO: 13, and the amino acid sequence of VH of clone 2B8 is as set forth in SEQ ID NO: 11. The amino acid sequence of VL of clone 4H3 is as set forth in SEQ ID NO: 63, and the amino acid sequence of VH of clone 4H3 is as set forth in SEQ ID NO: 61. The amino acid sequence of VL of clone 3E7 is as set forth in SEQ ID NO: 33; and the amino acid sequence of VH of clone 3E7 is as set forth in SEQ ID NO: 31. The amino acid sequence of VL of clone 1A8 is as set forth in SEQ ID NO: 3, and the amino acid sequence of VH of clone 1A8 is as set forth in SEQ ID NO: 1. The amino acid sequence of VL of clone 4G1 is as set forth in SEQ ID NO: 53, and the amino acid sequence of VH of clone 4G1 is as set forth in SEQ ID NO: 51. The amino acid sequence of VL of clone 2G3 is as set forth in SEQ ID NO: 73, and the amino acid sequence of VH of clone 2G3 is as set forth in SEQ ID NO: 71. The amino acid sequence of VL of clone 2F11 is as set forth in SEQ ID NO: 83, and the amino acid sequence of VH of clone 2F11 is as set forth in SEQ ID NO: 81. The amino acid sequence of VL of clone 3B8 is as set forth in SEQ ID NO: 43, and the amino acid sequence of VH of clone 3B8 is as set forth in SEQ ID NO: 41. 
     Example 3 Preparation of Anti-CD27 Chimeric Antibodies 
     The amino acid sequence of human IgG1 constant region was obtained according to the amino acid sequence of the human immunoglobulin gamma1 (hIgG1, and the accession number in Uniprot is P01857). The corresponding coding nucleic acid sequence was designed using the online tool DNAworks (http://helixweb.nih.gov/dnaworks/). The nucleic acid sequences encoding the VH of the selected antibodies from Example 2 were fused with the human IgG1 constant region sequences, respectively. The obtained fused sequences were then sub-cloned into the vector pcDNA4/myc-HisA to obtain the heavy chain expression plasmids for each antibody. 
     The amino acid sequence of human Kappa light chain constant region (Igκ) was obtained according to the amino acid sequence of the human immunoglobulin Kappa (the accession number in Uniprot is P01934). The corresponding coding nucleic acid sequence was designed using the online tool DNAworks (http://helixweb.nih.gov/dnaworks/). The nucleic acid sequences encoding for the VL of the selected antibodies from Example 2 were fused with the human Igκ constant region sequences, respectively. The obtained fused sequences were then sub-cloned into the vector pcDNA4/myc-HisA to obtain the light chain expression plasmids for each antibody. 
     The heavy chain and light chain plasmids obtained as described above were extracted using the plasmid extraction kit (PL14) provided by AidLab. The heavy chain and light chain plasmids were then co-transfected into HEK293 cells for antibody expression. Briefly, the expression plasmids were diluted with Freestyle 293 medium and the PEI (Polyethyleneimine) solution was added. The plasmid/PEI mixture was added to the cell suspension and incubated under 37° C., 10% CO 2  at 90 rpm, with 50 μg/L IGF-1 added. After four hours, EX293 medium, 2 mM Glutamine and 50 μg/L IGF-1 were added and incubated under 135 rpm. Twenty-four hours later, 3.8 m MVPA was added. After culturing for 5 to 6 days, transient expression culture supernatants were harvested and purified by ProteinA affinity chromatography to obtain anti-CD27 chimeric antibodies, which are named as m2E7, m2B8, m4H3, m3E7, m1A8, m4G1, m2G3, m2F11 and m3B8, respectively. 
     Example 4 Characterization of the Anti-CD27 Chimeric Antibodies 
     4.1 Binding to Cell Surface CD27 (FACS) 
     5×10 5  CD27-EGFP cells prepared in Example 1 were washed twice in PBS, 10 μg/ml of each chimeric antibody prepared in Example 3 (m2E7, m2B8, m4H3, m3E7, m1A8, m4G1, m2G3, m2F11 and m3B8) was added to the cells and incubated at 4° C. for 30 min. Then it was washed twice in PBS, anti-human Ig-APC (Jackson ImmunoResearch Laboratories, Cat #109-135-098) was added, incubated at 4° C. for 30 min, washed twice with PBS and resuspended in 300 μl PBS. It was then examined by flow cytometry, and the results are shown in  FIG. 1 . In  FIG. 1 , NC represents negative control (PBS), a-hlg-APC represents secondary antibody only, the other panels represent results obtained with each of the corresponding clone, respectively. 
     It can be seen from the results of  FIG. 1  that all the chimeric antibodies obtained from Example 3 could bind to cell surface CD27. 
     4.2 Binding Specificity to hCD27 (FACS) 
     The hCD137-EGFP, hOX40-EGFP and hGITR-EGFP cells as described in Example 1 were washed twice in PBS, 10 μg/ml of each chimeric antibody as prepared in Example 3 (m2E7, m2B8, m4H3, m3E7, m1A8, m4G1, m2G3, m2F11 and m3B8) was added to each type of cells and incubated at 4° C. for 30 min. Then it was washed twice with PBS, anti-human Ig-APC (Jackson ImmunoResearch Laboratories, Cat #109-135-098) was added and were incubated at 4° C. for 30 min, washed twice with PBS and resuspended in 300 μl PBS. Then, flow cytometry was performed, and the results are shown in  FIG. 2 . In  FIG. 2 , NC represents negative control (PBS), a-hlg-APC represents secondary antibody only, the other panels represent results obtained with each of the corresponding clone, respectively. 
     It can be seen from the results of  FIG. 2  that none of the chimeric antibodies prepared in Example 3 could substantially bind to hCD137, hOX40 or hGITR, demonstrating the binding specificity of the antibodies for hCD27. 
     4.3 Activation Assay 
     293T-CD27-NF-κB cells were digested with trypsin, after 2-3 mins, DMEM complete medium was added. The cells were gently suspended and transferred to 96-well plates, 100 μl/well. Supernatants from the 50 selected clones were mixed with anti-mouse crosslinking antibody (Jackson ImmunoResearch Laboratories: 109-006-008) and added to a 96-well plate. Complete medium was added to the control group. The cells were lysed after 30 hours and then tested using the luciferase assay system (Promega: E1501). 
     The results are shown in  FIGS. 3A-3B . The antibody 1F5 shown in  FIG. 3B  has been included as a benchmark control. It can be seen that all the chimeric antibodies prepared in Example 3 could activate downstream signaling and had a higher activation ability than the benchmark antibody 1F5. 
     4.4 Stimulation of T Cell Proliferation 
     Peripheral blood mononuclear cells (PBMCs) were isolated from peripheral blood concentrates of healthy donors by density gradient centrifugation using isolation solution for human lymphocytes (Tianjin Gengyang), and PBMCs were isolated with EasySep Negative Human CD4 Kit (stem cell: 19052) to obtain CD4 +  T cells. The cells were washed twice with PBS and cell number was counted. The cells were then labeled with CFSE (Biolegend, cat. NO: 422701) according to the Biolegend instructions, washed twice with PBS, counted, and added to a 96-well plate with 1.5×10 5  cells per well. The 96-well plate was pre-coated with 3 μg/ml anti-CD3 antibody and the chimeric antibodies prepared in Example 3, incubated at 4° C. overnight. The negative control was incubated only with the anti-CD3 antibody, and the positive control was incubated with a soluble anti-CD28 antibody. The cells were washed 3 times with PBS on the next day. After adding the CD4 +  T cells into the 96-well plate, the 96-well plates were placed in a CO 2  incubator and incubated for 5 days. Then, the cells were collected, and cell proliferation was examined with flow cytometry. The results are shown in the  FIG. 4A  and  FIG. 4B , the antibody 1F5 is a benchmark control. It can be seen from  FIGS. 4A-4B  that the clone m2F11 has the strongest activity in promoting T cell proliferation, which is even stronger than the benchmark antibody 1F5. 
     Example 5 Humanization of Anti-CD27 Antibodies 
     Based on the results obtained in the above examples, the clone m2F11 was selected, as an example, for humanization. The antibody was humanized by changing certain amino acid residues in the framework regions of the heavy chain variable regions and light chain variable regions. A total of 12 humanized heavy chain variable regions and 1 humanized light chain variable region were obtained, resulting in 12 humanized antibodies. The amino acid sequences of the 12 humanized antibodies are shown in Table 1 below: 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Humanized 
                   
                   
                   
                   
               
               
                 antibody 
                 VH 
                 SEQ ID NO: 
                 VL 
                 SEQ ID NO: 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 d16647 
                 d16647VH 
                 115 
                 16647VL 
                 91 
               
               
                 d12996 
                 d12996VH 
                 107 
                   
                   
               
               
                 d9419 
                 d9419VH 
                 95 
                   
                   
               
               
                 d9424 
                 d9424VH 
                 99 
                   
                   
               
               
                 d14822 
                 d14822VH 
                 111 
                   
                   
               
               
                 d12674 
                 d12674VH 
                 103 
                   
                   
               
               
                 16647 
                 16647VH 
                 113 
                   
                   
               
               
                 12996 
                 12996VH 
                 105 
                   
                   
               
               
                 9419 
                 9419VH 
                 93 
                   
                   
               
               
                 9424 
                 9424VH 
                 97 
                   
                   
               
               
                 14822 
                 14822VH 
                 109 
                   
                   
               
               
                 12674 
                 12674VH 
                 101 
               
               
                   
               
            
           
         
       
     
     5.1 Expression and Purification of Humanized Antibodies 
     Nucleic acid molecules encoding the humanized VH and VL were synthesized. The nucleic acids encoding VH and that encoding the human IgG1 heavy chain constant region were fused to obtain the sequence encoding the antibody heavy chain, and the nucleic acids encoding VL and that encoding the human kappa light chain constant region were fused to obtain the sequence encoding the antibody light chain, as described in Example 3 for the chimeric antibodies. The obtained nucleic acid molecules were then cloned into the vector pcDNA4/myc-HisA, respectively, to obtain 12 heavy chain expression plasmids and one light chain expression plasmid. Each heavy chain expression plasmid was paired with a light chain expression plasmid and they were transiently transfected into the HEK293 cells (ATCC, CRL-1573™) for protein production. Briefly, the expression plasmids were diluted with Freestyle 293 medium and the PEI (Polyethyleneimine) solution was added. The plasmid/PEI mixture was added to the cell suspension and incubated under 37° C., 10% CO 2  at 90 rpm. After culturing for 5 to 6 days, transient expression culture supernatants were harvested and purified by ProteinA affinity chromatography to obtain the 12 humanized antibodies: d16647, d12996, d9419, d9424, d14822, d12674, 16647, 12996, 9419, 9424, 14822 and 12674, which would be used in the following examples. The obtained humanized antibodies were verified by SDS-PAGE ( FIGS. 13A-13F ) and the target bands were clearly seen. The yield of the humanized antibodies is shown in Table 2. 
       FIGS. 13A-13F  showed that humanized antibodies d16647, 16647, d9419, 9419, 9424, d12996, 14822, 12674, d12674, 12996, d14822 was successfully expressed and purified. In  FIG. 13A , lane 1 was loaded with 16647 (original sample); lane 2 was loaded with 16647 (flow-through); lane 3 was loaded with 16647 (eluted); lane 4 was loaded with marker (26630); lane 5 was loaded with d16647 (eluted); lane 6 was loaded with d16647 (original sample); lane 7 was loaded with d16647 (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was blank; lane 10 was empty; lane 11 was loaded with 16647 (eluted, non-reducing); and lane 12 was loaded with d16647 (eluted, non-reducing). 
     In  FIG. 13B , lane 1 was loaded with d9419 (original sample); lane 2 was loaded with d9419 (flow-through); lane 3 was loaded with d9419 (eluted); lane 4 was loaded with marker (26619); lane 5 was loaded with 1 μg Std; lane 6 was blank; lane 7 was empty and lane 8 was loaded with d9419 (eluted, non-reducing). 
     In  FIG. 13C , lane 1 was loaded with 9419 (original sample); lane 2 was loaded with 9419 (flow-through); lane 3 was loaded with 9419 (eluted); lane 4 was loaded with marker (26630); lane 5 was loaded with 9424 (eluted); lane 6 was loaded with 9424 (original sample); lane 7 was loaded with 9424 (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was blank; lane 10 was empty; lane 11 was loaded with 9419 (eluted, non-reducing); and lane 12 was loaded with 94924 (eluted, non-reducing). 
     In  FIG. 13D , lane 1 was loaded with d12996 (original sample); lane 2 was loaded with d12996 (flow-through); lane 3 was loaded with d12996 (eluted); lane 4 was loaded with marker (26619); lane 5 was loaded with 14822 (eluted); lane 6 was loaded with 14822 (original sample); lane 7 was loaded with 14822 (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was blank; lane 10 was empty; lane 11 was loaded with d12996 (eluted, non-reducing); and lane 12 was loaded with 14822 (eluted, non-reducing). 
     In  FIG. 13E , lane 1 was loaded with 12674 (original sample); lane 2 was loaded with 12674 (flow-through); lane 3 was loaded with 12674 (eluted); lane 4 was loaded with marker (26630); lane 5 was loaded with d12674 (eluted); lane 6 was loaded with d12674 (original sample); lane 7 was loaded with d12674 (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was blank; lane 10 was empty; lane 11 was loaded with 12674 (eluted, non-reducing); and lane 12 was loaded with d12674 (eluted, non-reducing). 
     In  FIG. 13F , lane 1 was loaded with 12996 (original sample); lane 2 was loaded with 12996 (flow-through); lane 3 was loaded with 12996 (eluted); lane 4 was loaded with marker (26619); lane 5 was loaded with d14822 (eluted); lane 6 was loaded with d14822 (original sample); lane 7 was loaded with d14822 (flow-through); lane 8 was loaded with 1 μg Std; lane 9 was blank; lane 10 was empty; lane 11 was loaded with 12996 (eluted, non-reducing); and lane 12 was loaded with d14822 (eluted, non-reducing). 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Antibody 
                 Yield (μg/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 m2F11 
                 91.2 
               
               
                   
                 d16647 
                 43 
               
               
                   
                 d12996 
                 7.28 
               
               
                   
                 d9419 
                 22.32 
               
               
                   
                 d9424 
                 5 
               
               
                   
                 d14822 
                 114.6 
               
               
                   
                 d12674 
                 132.6 
               
               
                   
                 16647 
                 13.2 
               
               
                   
                 12996 
                 32 
               
               
                   
                 9419 
                 16 
               
               
                   
                 9424 
                 29.2 
               
               
                   
                 14822 
                 44 
               
               
                   
                 12674 
                 79.92 
               
               
                   
                   
               
            
           
         
       
     
     5.2 Binding of the Humanized Antibodies to Human CD27 (ELISA) 
     The ELISA plate was coated with 2 μg/ml hCD27-muFc, 100 μl/well and incubated at 4° C. overnight. Then it was washed once with 10 mM, pH 7.4 PBS/Tween (0.05%), blocked with PBST containing 5% skimmed milk powder and incubated at 37° C. for 2 h. After washing the plate for 4 times, the humanized antibodies were added and incubated at 37° C. for 40 min, then it was washed for 4 times. Anti-human IgG-HRP-conjugated secondary antibody (Sigma, Cat #A0170-1M) was added and incubated at 37° C. for 40 min. After washing, the plate was developed with TMB substrate and spectrophotometric analysis was performed at OD 450 . The results are shown in the  FIGS. 5A-5B . and Table 3. In  FIGS. 5A-5B , each curve represents the binding result obtained for one of the humanized antibodies. From the results, it can be seen that all these humanized antibodies could bind to human CD27. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Antibody  
                 Human CD27 EC 50  (ng/ml) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Test 1 
               
            
           
           
               
               
               
            
               
                   
                 m2F11 
                 31.51 
               
               
                   
                 d16647 
                 37.58 
               
               
                   
                 d12996 
                 30.02 
               
               
                   
                 d9419 
                 33.04 
               
               
                   
                 12996 
                 50.58 
               
               
                   
                 9419 
                 58.33 
               
               
                   
                 14822 
                 42.73 
               
               
                   
                 12674 
                 58.52 
               
            
           
           
               
            
               
                 Test 2 
               
            
           
           
               
               
               
            
               
                   
                 m2F11 
                 27.88 
               
               
                   
                 d14822 
                 33.87 
               
               
                   
                 d12674 
                 42.41 
               
               
                   
                 16647 
                 44.51 
               
               
                   
                 9424 
                 34.16 
               
               
                   
                   
               
            
           
         
       
     
     5.3 Binding to Cell Surface CD27 (FACS) 
     Based on the above results of ELISA, 7 humanized antibodies were selected to examine their affinities to cell surface CD27. Briefly, 5×10 5  CD27-EGFP cells prepared in Example 1 were washed twice in PBS, each of the humanized antibodies (d16647, d12996, d9419, 14822, 9424, d14822, d12674) was added. The antibodies were subjected to 3-fold serial dilution, starting from 20 μg/ml, to obtain 8 gradient dilutions for each antibody. The antibodies and the cells were incubated at 4° C. for 30 min. Then, it was washed twice with PBS, anti-human Ig-APC (Jackson ImmunoResearch Laboratories, Cat #109-135-098) was added, and incubated at 4° C. for 30 min, washed twice with PBS and resuspended in 300 μl PBS. Flow cytometry was then performed, and the results are shown in  FIG. 6 . m2F11 was used as a control. 
     It can be seen from the results of  FIG. 6  that all these humanized antibodies could bind to cell surface CD27. 
     5.4 Binding Kinetics to Human CD27 Protein 
     Using the BLI method, each humanized antibody was immobilized on a Protein A biosensor at a concentration of 10 μg/ml, while hCD27-muFc was subjected to 2-fold serial dilution, starting from 100 nM, to obtain 5 gradient dilutions for each antibody. The reaction plate was placed on the Octet K2 instrument. The parameters were set to Baseline 70 s, Association 80 s, Dissociation 300 s, Baseline 260 s, Loading 40 s, and Custom 5 s. The results are shown in Table 4. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Antibodies 
                 KD (M) 
                 K on  (1/Ms) 
                 K off  (1/s) 
               
               
                   
                   
               
             
            
               
                   
                 m2F11 
                 8.35 × 10 −10   
                 1.30 × 10 5   
                 1.08 × 10 −4   
               
               
                   
                 d16647 
                 3.05 × 10 −9   
                 9.21 × 10 4   
                 2.81 × 10 −4   
               
               
                   
                 d12996 
                 3.39 × 10 −9   
                 9.62 × 10 4   
                 3.26 × 10 −4   
               
               
                   
                 d9419 
                 1.70 × 10 −9   
                 1.20 × 10 5   
                 2.05 × 10 −4   
               
               
                   
                 d14822 
                 4.27 × 10 −9   
                 7.82 × 10 4   
                 3.34 × 10 −4   
               
               
                   
                 d12674 
                 5.00 × 10 −9   
                 8.94 × 10 4   
                 4.47 × 10 −4   
               
               
                   
                 16647 
                 4.86 × 10 −9   
                 7.15 × 10 4   
                 3.48 × 10 −4   
               
               
                   
                 12996 
                 4.98 × 10 −9   
                 7.39 × 10 4   
                 3.68 × 10 −4   
               
               
                   
                 9419 
                 2.73 × 10 −9   
                 1.05 × 10 5   
                 2.87 × 10 −4   
               
               
                   
                 9424 
                 7.02 × 10 −9   
                 5.65 × 10 4   
                 3.96 × 10 −4   
               
               
                   
                 14822 
                 5.15 × 10 −9   
                 9.70 × 10 4   
                 4.99 × 10 −4   
               
               
                   
                 12674 
                 3.66 × 10 −9   
                 7.95 × 10 4   
                 2.91 × 10 −4   
               
               
                   
                   
               
            
           
         
       
     
     5.5 Binding to Monkey Cell Surface CD27 (FACS) 
     5×10 5  RhCD27-EGFP cells as prepared in Example 1 were washed twice with PBS, 10 μg/ml humanized antibody prepared in Example 5 (d9419, d16647, d14822, d12674) was added and incubated at 4° C. for 30 min. Then it was washed twice with PBS, anti-human Ig-APC (Jackson ImmunoResearch Laboratories, Cat #109-135-098) was added and incubate at 4° C. for 30 min, washed twice with PBS and was resuspended in 300 μl PBS. Then flow cytometry was performed, and the results are shown in  FIG. 7 . m2F11 was used as a control. 
     It can be seen from the results of  FIG. 7  that these humanized antibodies could bind to monkey cell surface RhCD27. 
     5.6 Activation Assay 
     293T-CD27-NF-κB cells were digested with trypsin, after 2-3 mins, DMEM complete medium was added. The cells were gently suspended and transferred to 96-well plates, 100 μl/well. The humanized antibodies prepared in Example 5 were subjected to 10-fold dilution, starting from 10 μg/ml, and the diluted antibodies were mixed with the anti-human crosslinking antibody (Jackson Immuno Research Laboratories: 109-006-008) and added to a 96-well plate. Complete medium was added into the control group. The cells were lysed after 30 hours and then tested using the luciferase assay system (Promega: E1501). The results are shown in  FIG. 8 , and every curve in  FIG. 8  represents the result obtained for one humanized antibody, m2F11 was used as a control. 
     It can be seen from the results in  FIG. 8  that the humanized antibodies could still activate downstream signaling. 
     5.7 Stimulation of T Cell Proliferation 
     Peripheral blood mononuclear cells (PBMCs) were isolated from peripheral blood concentrates of healthy donors by density gradient centrifugation using isolation solution for human lymphocytes (Tianjin Gengyang), and PBMCs were isolated with EasySep Negative Human CD4 Kit (stem cell: 19052) to obtain CD4 +  T cells. The cells were washed twice with PBS and cell number was counted. The cells were then labeled with CFSE (Biolegend, cat. NO: 422701) according to the Biolegend instructions, washed twice with PBS, counted, and added to a 96-well plate with 1.5×10 5  cells per well. The 96-well plate was pre-coated with 3 μg/ml anti-CD3 antibody and the chimeric antibodies prepared in Example 3, incubated at 4° C. overnight. The negative control was incubated only with the anti-CD3 antibody, and the positive control was incubated with a soluble anti-CD28 antibody. The cells were washed 3 times with PBS on the next day. After adding the CD4 +  T cells into the 96-well plate, the 96-well plates were placed in a CO 2  incubator and incubated for 5 days. Then, the cells were collected, and cell proliferation was examined with flow cytometry. In addition, the supernatant was collected and the secretion of IFN-γ in the supernatant was examined using a CBA detection kit (BD, cat. NO: 551809). 
     The results are shown in the  FIG. 9A  and  FIG. 9B .  FIG. 9A  shows that the anti-CD27 humanized antibodies could stimulate T cell proliferation, even more significant than the antibody m2F11.  FIG. 9B  shows that the anti-CD27 humanized antibodies could stimulate secretion of IFN-γ by T cells. 
     Example 6 Antibody Stability 
     6.1 Testing of Antibody Stability by Differential Scanning Calorimetry (DSC) 
     DSC was used to test the thermal stability of the humanized antibodies. The DSC scanning results obtained with buffer only and that with buffers comprising proteins were obtained as control. Each humanized antibody was diluted to 1 mg/ml (PBS buffer). The following parameters were used: 10-110° C., 100° C. per hour, 15 min balancing time before each scan. The sample volume was 0.5 ml. The results were calibrated against the scanning data collected with the buffer only, and those with the buffer comprising proteins. Then, the T m  values of the humanized antibodies were obtained, as shown in Table 5. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Antibodies 
                 T m  (° C.) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 m2F11 
                 65.7 
               
               
                   
                 d16647 
                 67 
               
               
                   
                 d12996 
                 59.5 
               
               
                   
                 d9419 
                 66.5 
               
               
                   
                 d14822 
                 67.5 
               
               
                   
                 d12674 
                 68 
               
               
                   
                 16647 
                 65.5 
               
               
                   
                 12996 
                 64.5 
               
               
                   
                 9419 
                 64.2 
               
               
                   
                 9424 
                 66.8 
               
               
                   
                 14822 
                 66.2 
               
               
                   
                 12674 
                 66.7 
               
               
                   
                   
               
            
           
         
       
     
     6.2 Accelerated Stabilization Test 
     45° C. accelerated stabilization test was performed for the humanized antibodies. Briefly, one-step ProteinA purified antibodies were dissolved in PBS (pH 7.4), and the antibody was concentrated to approximately 10 mg/ml. 100 μg antibody was added into a 200 μl PCR tube, incubated at 45° C. Samples were taken on day 0, day 10, day 20, and day 30 for detection under A280 and SEC-HPLC analysis. The results are shown in  FIG. 10  and  FIG. 11 , respectively.  FIG. 10  shows change of the antibody concentration with time, and  FIG. 11  shows change of the percentage of antibody dimers with time. It can be seen from these results that the antibody concentration did not change significantly with time, and the percentage of antibody dimers has not changed significantly with time. In addition, formation of trimers or aggregations was not observed. 
     While preferred embodiments of the present application have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the application be limited by the specific examples provided within the specification. While the application has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the application. Furthermore, it shall be understood that all aspects of the application are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the application described herein may be employed in practicing the application. It is therefore contemplated that the application shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the application and that methods and structures within the scope of these claims and their equivalents be covered thereby.