Patent Publication Number: US-2021187022-A1

Title: Engineered t cells for the treatment of cancer

Description:
CROSS-REFERENCE 
     This application is a National Phase Entry Application of PCT/US2017/068002, filed Dec. 21, 2017, which claims the benefit of U.S. Provisional Application No. 62/437,524, filed Dec. 21, 2016, each of which is incorporated herein by reference in its entirety. 
    
    
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Mar. 9, 2018, is named 48538-710_601_SL.txt and is 55,511 bytes in size. 
     BACKGROUND 
     Most patients with late-stage solid tumors are incurable with standard therapy. In addition, traditional treatment options often have serious side effects. Numerous attempts have been made to engage a patient&#39;s immune system for rejecting cancerous cells, an approach collectively referred to as cancer immunotherapy. However, several obstacles make it rather difficult to achieve clinical effectiveness. Although hundreds of so-called tumor antigens have been identified, these are often derived from self and thus can direct the cancer immunotherapy against healthy tissue, or are poorly immunogenic. Furthermore, cancer cells use multiple mechanisms to render themselves invisible or hostile to the initiation and propagation of an immune attack by cancer immunotherapies. 
     Adoptive T cell therapy (ACT) is a powerful approach to treat even advanced stages of metastatic cancer (Rosenberg, Nat Rev Clin Oncol 8(10) (2011). For ACT, antigen-specific T cells are isolated or engineered and are expanded in vitro prior to reinfusion to the patient (Gattinoni et al., Nat Rev Immunol 6(5) (2006). In clinical trials, unparalleled response rates in some cancer patients have been achieved by ACT in conjunction with total body irradiation. However, the majority of patients do not respond to this treatment (Dudley et al., J Clin Oncol 26(32) (2008); Rosenberg et al., Clin Cancer Res 17(13) (2011). Tumor-induced immunosuppression which is not counteracted by total body irradiation has been implicated in this resistance to therapy (Leen et al., Annu Rev Immunol 25 (2007). Recently, inhibitory receptors upregulated on activated T cells and their respective ligands expressed within the tumor milieu have shown to contribute to T cell therapy failure (Abate-Daga et al., Blood 122(8) (2013). Among the inhibitory receptors, the programmed death receptor-1 (PD-1) plays a central role, given that recent studies have identified PD-1 expressed on tumor-antigen-specific T cells in tumors (Gros et al., J Clin Invest (2014)). The interaction of PD-1 with its ligand PD-L1 suppresses TCR signaling and T cell activation and thus prevents effective activation upon target recognition (Gros et al., J Clin Invest (2014); Yokosuka et al., J Exp Med 209(6) (2012); Ding et al., Cancer Res (2014); Karyampudi et al., Cancer Res (2014)). The clinical weight of these mechanisms is underlined by therapeutic studies combining ACT or gene-modified T cells with antibody-based PD-1 blockade that result in a marked improvement of anti-tumor activity (John et al., Clin Cancer Res 19(20) (2013); Goding et al., J Immunol 190(9) (2013). The systemic application of PD-1- or PD-L1-blocking antibodies has the disadvantage of potentially targeting T cells of any reactivity and thus of inducing systemic side effects (Topalian et al., N Engl J Med 366(26) (2012); Brahmer et al., N Engl J Med 366(26) (2012)). 
     In view of the PD-L1-mediated T cell inhibition, there is still a need to provide improved means having the potential to improve safety and efficacy of ACT and overcome the above disadvantages. Described herein are engineered T cells comprising PD-1 fusion proteins and modified T cell receptors that are designed to address this need. 
     SUMMARY 
     Provided herein are fusion proteins and combinations thereof for T cell engineering, T-cell receptor (TCR) fusion proteins (TFPs), fusion proteins comprising PD-1 and a co-stimulatory domain, T cells engineered to express one or more TFPs and a fusion protein comprising PD-1 and a co-stimulatory domain, and methods of use thereof for the treatment of diseases. 
     In one aspect, provided herein is an isolated recombinant nucleic acid molecule encoding a T-cell receptor (TCR) fusion protein (TFP) comprising a TCR subunit and a human or humanized antibody domain comprising an PD-1 polypeptide or fragment thereof. 
     In one aspect, provided herein is a composition comprising a first isolated recombinant nucleic acid molecule encoding a first fusion protein comprising a TCR subunit comprising at least a portion of a TCR extracellular domain, and a TCR intracellular domain comprising a stimulatory domain from an intracellular signaling domain of a CD3 subunit; and a first target binding domain, wherein the TCR subunit and the first target binding domain are operatively linked, and wherein the first fusion protein incorporates into a TCR when expressed in a T-cell; and a second isolated recombinant nucleic acid molecule encoding a second fusion protein having a second target binding domain, wherein the second target binding domain comprises a PD-1 polypeptide which is operably linked via its C-terminus to the N-terminus of an intracellular domain of a costimulatory polypeptide, wherein the PD-1 polypeptide comprises the extracellular domain and the transmembrane domain of PD-1. In some embodiments, the first target binding domain is a human or humanized antibody domain. 
     In one aspect, provided herein is a composition comprising a first isolated recombinant nucleic acid molecule encoding a first T-cell receptor (TCR) fusion protein (TFP) comprising a TCR subunit having at least a portion of a TCR extracellular domain, and a TCR intracellular domain comprising a stimulatory domain from an intracellular signaling domain of a CD3 subunit; and a first human or humanized antibody domain comprising a first antigen binding domain and, optionally, a second human or humanized antibody domain comprising a second antigen binding domain; wherein the TCR subunit, the first antibody domain, and the second antibody domain are operatively linked, and wherein the first TFP incorporates into a TCR when expressed in a T-cell; and a second isolated recombinant nucleic acid molecule encoding a second fusion protein having a second target binding domain, wherein the second target binding domain comprises a PD-1 polypeptide which is operably linked via its C-terminus to the N-terminus of an intracellular domain of a costimulatory polypeptide, wherein the PD-1 polypeptide comprises the extracellular domain and the transmembrane domain of PD-1. In some embodiments, the antibody domain is capable of specifically binding a tumor-associated antigen selected from the group consisting of ROR-1, BCMA, CD19, CD20, CD22, mesothelia, MAGE A3, EGFRvIII, MUC16, NKG2D, I1-13Rα2, L1CAM, and NY-ESO-1, and combinations thereof. In some embodiments, the costimulatory polypeptide is selected from the group consisting of OX40, CD2, CD27, CDS, ICAM-1, ICOS (CD278), 4-1BB (CD137), GITR, CD28, CD30, CD40, BAFFR, HVEM, CD7, LIGHT, NKG2C, SLAMF7, NKp80, CD160, CD226, FcγRI, FcγRII, and FcγRIII. 
     In one aspect, provided herein is a viral vector comprising a first and a second nucleic molecule described herein. In some embodiments, the first isolated recombinant nucleic acid molecule and the second isolated recombinant nucleic acid molecule are contained in a single operon. 
     In some embodiments, the first isolated recombinant nucleic acid molecule and the second isolated recombinant nucleic acid molecule are contained in two separately transcribed operons. 
     In some embodiments, the operon comprises an E1a promoter. In some embodiments, the operons each comprise an E1a promoter. In some embodiments, the viral vector is a DNA, an RNA, a plasmid, a lentivirus vector, adenoviral vector, a Rous sarcoma viral (RSV) vector, or a retrovirus vector. 
     In one aspect, provided herein is a viral vector comprising a first isolated recombinant nucleic acid molecule described herein. 
     In one aspect, provided herein is a viral vector comprising a second isolated recombinant nucleic acid molecule described herein. 
     In one aspect, provided herein is a mixture comprising a viral vector described herein. 
     In one aspect, provided herein is a transduced T cell comprising a composition described herein or a viral vector described herein or a mixture described herein. 
     In one aspect, provided herein is a transduced T cell comprising one or more viral vectors described herein. In some embodiments, the first fusion protein and the second fusion protein are each detectable on the surface of the T cell. 
     In one aspect, provided herein is an isolated T cell comprising a plurality of polypeptides, a first polypeptide comprising a TCR subunit comprising at least a portion of a TCR extracellular domain, a TCR intracellular domain comprising a stimulatory domain from an intracellular signaling domain of CD3 epsilon or CD3 gamma; and a first target binding domain, wherein the TCR subunit and the first target binding domain are operatively linked, and wherein the first fusion protein is incorporated into a TCR in the T cell; and a second fusion protein having a second target binding domain, wherein the second target binding domain comprises a PD-1 polypeptide which is operably linked via its C-terminus to the N-terminus of an intracellular domain of a costimulatory polypeptide, wherein the PD-1 polypeptide comprises the extracellular domain and the transmembrane domain of PD-1. 
     In some embodiments, the first target binding domain is selected from the group consisting of CD16, BCMA, MSLN, NKG2D, ROR1, CD19, CD20, CD22, and prostate specific cancer antigen (PSCA). In some embodiments, the costimulatory polypeptide is selected from the group consisting of OX40, CD2, CD27, CDS, ICAM-1, ICOS (CD278), 4-1BB (CD137), GITR, CD28, CD30, CD40, BAFFR, HVEM, CD7, LIGHT, NKG2C, SLAMF7, NKp80, CD160, CD226, FcγRI, FcγRII, and FcγRIII. In some embodiments, the costimulatory polypeptide of the second fusion protein is CD28. 
     In some embodiments, the encoded first antigen binding domain is connected to the TCR extracellular domain of the first TFP by a first linker sequence and the encoded second antigen binding domain is connected to the TCR extracellular domain of the first TFP by a second linker sequence. In some embodiments, the first linker sequence and the second linker sequence comprise (G4S)n, wherein n=1 to 4 (SEQ ID NO: 19). 
     In some embodiments, the TCR subunit of the first TFP comprises a TCR extracellular domain. In some embodiments, the TCR subunit of the first TFP comprises a TCR transmembrane domain. In some embodiments, the TCR subunit of the first TFP comprises a TCR intracellular domain. In some embodiments, the TCR subunit of the first TFP comprises (i) a TCR extracellular domain, (ii) a TCR transmembrane domain, and (iii) a TCR intracellular domain, wherein at least two of (i), (ii), and (iii) are from the same TCR subunit. 
     In some embodiments, the TCR subunit of the first TFP comprises a TCR intracellular domain comprising a stimulatory domain selected from an intracellular signaling domain of CD3 epsilon, CD3 gamma or CD3 delta, or an amino acid sequence having at least one modification thereto. In some embodiments, the TCR subunit of the first TFP comprises an intracellular domain comprising a stimulatory domain selected from a functional signaling domain of 4-1BB and/or a functional signaling domain of CD3 zeta, or an amino acid sequence having at least one modification thereto. 
     In some embodiments, the first human or humanized antibody domain, the second human or humanized antibody domain, or both comprise an antibody fragment. In some embodiments, the first human or humanized antibody domain, the second human or humanized antibody domain, or both comprise a scFv or a VH domain. In some embodiments, the encoded first TFP includes an extracellular domain of a TCR subunit that comprises an extracellular domain or portion thereof of a protein selected from the group consisting of a TCR alpha chain, a TCR beta chain, a CD3 epsilon TCR subunit, a CD3 gamma TCR subunit, a CD3 delta TCR subunit, functional fragments thereof, and amino acid sequences thereof having at least one but not more than 20 modifications. 
     In some embodiments, the encoded first TFP includes a transmembrane domain that comprises a transmembrane domain of a protein selected from the group consisting of a TCR alpha chain, a TCR beta chain, a CD3 epsilon TCR subunit, a CD3 gamma TCR subunit, a CD3 delta TCR subunit, functional fragments thereof, and amino acid sequences thereof having at least one but not more than 20 modifications. In some embodiments, the encoded first TFP includes a transmembrane domain that comprises a transmembrane domain of a protein selected from the group consisting of a TCR alpha chain, a TCR beta chain, a TCR zeta chain, a CD3 epsilon TCR subunit, a CD3 gamma TCR subunit, a CD3 delta TCR subunit, CD45, CD4, CD5, CD8, CD9, CD16, CD22, CD33, CD28, CD37, CD64, CD80, CD86, CD134, CD137, CD154, functional fragments thereof, and amino acid sequences thereof having at least one but not more than 20 modifications. 
     In some embodiments, the isolated nucleic acid molecule further comprises a sequence encoding a costimulatory domain. In some embodiments, the costimulatory domain is a functional signaling domain obtained from a protein selected from the group consisting of OX40, CD2, CD27, CD28, CDS, ICAM-1, LFA-1 (CD11a/CD18), ICOS (CD278), and 4-1BB (CD137), and amino acid sequences thereof having at least one but not more than 20 modifications thereto. 
     In some embodiments, the isolated nucleic acid molecule further comprises a sequence encoding an intracellular signaling domain. In some embodiments, the isolated nucleic acid molecule further comprises a leader sequence. 
     In some embodiments, the at least one but not more than 20 modifications thereto comprise a modification of an amino acid that mediates cell signaling or a modification of an amino acid that is phosphorylated in response to a ligand binding to the first TFP. 
     In some embodiments, the isolated nucleic acid molecule is an mRNA. 
     In some embodiments, the first TFP includes an immunoreceptor tyrosine-based activation motif (ITAM) of a TCR subunit that comprises an ITAM or portion thereof of a protein selected from the group consisting of CD3 zeta TCR subunit, CD3 epsilon TCR subunit, CD3 gamma TCR subunit, CD3 delta TCR subunit, TCR zeta chain, Fc epsilon receptor 1 chain, Fc epsilon receptor 2 chain, Fc gamma receptor 1 chain, Fc gamma receptor 2a chain, Fc gamma receptor 2b1 chain, Fc gamma receptor 2b2 chain, Fc gamma receptor 3a chain, Fc gamma receptor 3b chain, Fc beta receptor 1 chain, TYROBP (DAP12), CD5, CD16a, CD16b, CD22, CD23, CD32, CD64, CD79a, CD79b, CD89, CD278, CD66d, functional fragments thereof, and amino acid sequences thereof having at least one but not more than 20 modifications thereto. In some embodiments, the ITAM replaces an ITAM of CD3 gamma, CD3 delta, or CD3 epsilon. In some embodiments, the ITAM is selected from the group consisting of CD3 zeta TCR subunit, CD3 epsilon TCR subunit, CD3 gamma TCR subunit, and CD3 delta TCR subunit and replaces a different ITAM selected from the group consisting of CD3 zeta TCR subunit, CD3 epsilon TCR subunit, CD3 gamma TCR subunit, and CD3 delta TCR subunit. 
     In some embodiments, the nucleic acid comprises a nucleotide analog. In some embodiments, the nucleotide analog is selected from the group consisting of 2′-O-methyl, 2′-O-methoxyethyl (2′-O-MOE), 2′-O-aminopropyl, 2′-deoxy, T-deoxy-2′-fluoro, 2′-O-aminopropyl (2′-O-AP), 2′-O-dimethylaminoethyl (2′-O-DMAOE), 2′-O-dimethylaminopropyl (2′-O-DMAP), T-O-dimethylaminoethyloxyethyl (2′-O-DMAEOE), 2′-O—N-methylacetamido (2′-O-NMA) modified, a locked nucleic acid (LNA), an ethylene nucleic acid (ENA), a peptide nucleic acid (PNA), a 1′,5′-anhydrohexitol nucleic acid (HNA), a morpholino, a methylphosphonate nucleotide, a thiolphosphonate nucleotide, and a 2′-fluoro N3-P5′-phosphoramidite. 
     In some embodiments, the isolated nucleic acid molecule further comprises a leader sequence. 
     In one aspect, provided herein is a plurality of isolated polypeptide molecules encoded by a nucleic acid molecule described herein. In some embodiments, the vector is an in vitro transcribed vector. In some embodiments, the nucleic acid sequence in the vector further encodes a poly(A) tail. In some embodiments, the nucleic acid sequence in the vector further encodes a 3′UTR. 
     In one aspect, provided herein is a pharmaceutical composition comprising a plurality of nucleic acids, comprising a vector described herein, a mixture described herein, or a T cell described herein. 
    
    
     DETAILED DESCRIPTION 
     In one aspect, described herein are combinations of fusion proteins for use in engineering T cells for adoptive T cell therapy. The engineered T cells disclosed herein comprise expression of a modified T cell receptor (TCR) having a polypeptide capable of binding to a target cell, i.e., a cell capable of specifically binding to a cell characterized by an antigen, e.g., a tumor associated antigen. Such modified T cell receptors are described in detail in, e.g., co-pending International Non-Provisional Application Serial No. PCT/US2016/033146, filed May 18, 2016, herein incorporated by reference. 
     The engineered T cells disclosed herein also comprise a PD-1 fusion protein, which comprises the extracellular domain and the transmembrane domain of PD-1 operably linked via its C-terminus to the N-terminus of an intracellular domain of a co-stimulatory polypeptide. Suitable examples of co-stimulatory polypeptides are described below. In one embodiment, the co-stimulatory polypeptide is a CD28 polypeptide thus providing a “PD1CD28 fusion protein” or “PD1CD28 switch-receptor”. Other non-limiting examples of fusion proteins include a PD141BB switch-receptor, or a PD1X switch-receptor, wherein X is DAP10, DAP12, CD30, LIGHT, OX40, CD2, CD27, CDS, ICAM-1, LFA-1 (CD11a/CD18), or ICOS (CD278). 
     In one embodiment, the T cells expressing the modified TCR are capable of binding to a tumor cell expressing a tumor associated antigen (also herein, “TAA”), non-limiting examples of which are mesothelin (MSLN), B cell maturationMUC16 antigen (BCMA), CD19, CD20, CD22, prostate specific cancer antigen (PSCA), 5T4, 8H9, αvβθ integrin, αvβ6 integrin, alphafetoprotein (AFP), B7-H6, CA-125 carbonic anhydrase 9 (CA9), CD19, CD20, CD22, CD30, CD33, CD38, CD44, CD44v6, CD44v7/8, CD52, CD123, CD171, carcinoembryonic antigen (CEA), EpCAM (epithelial cell adhesion molecule), E-cadherin, EMA (epithelial membrane antigen), EGFRv111, epithelial glycoprotein-2 (EGP-2), epithelial glycoprotein-40 (EGP-40), ErbB1/EGFR, ErbB2/HER2/neu/EGFR2, ErbB3/HER3, ErbB4, epithelial tumor antigen (ETA), folate binding protein (FBP), fetal acetylcholine receptor (AchR), folate receptor-α, G250/CAIX, ganglioside 2 (GD2), ganglioside 3 (GD3), high molecular weight melanoma-associated antigen (HMW-MAA), IL-13 receptor a2 (IL-13Rα2), kinase insert domain receptor (KDR), k-light chain, Lewis Y (LeY), L1 cell adhesion molecule, melanoma-associated antigen (MAGE-A1), mesothelin, mucin-1 (MUC1), mucin-16 (MUC16), mucin-18 (MUC-18), natural killer group 2 member D (NKG2D) ligands, nerve cell adhesion molecule (NCAM), NY-ESO-1, oncofetal antigen (h5T4), prostate stem cell antigen (PSCA), prostate-specific membrane antigen (PSMA), receptor-tyrosine kinase-like orphan receptor 1 (ROR1), TAA targeted by mAb IgE, tumor-associated glycoprotein-72 (TAG-72), tyrosinase, and vascular endothelial growth factor (VEGF) receptors. Such T cells would comprise a modified T cell receptor comprising an scFv or VH domain capable of specifically binding a tumor associated antigen. 
     In another embodiment, the TCR comprises a CD16 polypeptide, or Fc binding fragment thereof, in place of an scFv or VH domain specific to a target antigen. T cells engineered to express such TCRs are useful for targeting a number of different types of tumor cells having surface antigen expression when combined with an antibody to said antigen, as the CD16 moiety is capably of binding to the IgG1 format antibody. 
     In another embodiment, the TCR comprises a TFP having more than one scFv or V H  domain specific to a cell surface antigen or tumor-associated antigen. Such TFPs are termed “dual specificity” TFPs, and thus enable the T cell expressing the engineered TCR to bind to more than one type of cancer cell, or more than one tumor-associated antigen on a single cancer cell. 
     In another embodiment, the TCR comprises an NKG2D polypeptide or fragment thereof. 
     In some embodiments, the TFP includes an extracellular domain of a TCR subunit that comprises an extracellular domain or portion thereof of a protein selected from the group consisting of the alpha or beta chain of the T-cell receptor, CD3 delta, CD3 epsilon, or CD3 gamma, or a functional fragment thereof, or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. In other embodiments, the encoded TFP includes a transmembrane domain that comprises a transmembrane domain of a protein selected from the group consisting of the alpha, beta chain of the TCR or TCR subunits CD3 epsilon, CD3 gamma and CD3 delta, or a functional fragment thereof, or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. 
     In some embodiments, the encoded TFP includes a transmembrane domain that comprises a transmembrane domain of a protein selected from the group consisting of the alpha, beta or zeta chain of the TCR or CD3 epsilon, CD3 gamma and CD3 delta CD45, CD4, CDS, CD8, CD9, CD16, CD22, CD33, CD28, CD37, CD64, CD80, CD86, CD134, CD137 and CD154, or a functional fragment thereof, or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. 
     In some embodiments, the encoded anti-tumor antigen binding domain, CD16 domain, or NKG2D domain, is connected to the TCR extracellular domain by a linker sequence. In some instances, the encoded linker sequence comprises (G4S)n, wherein n=1 to 4 (SEQ ID NO: 19). In some instances, the encoded linker sequence comprises a long linker (LL) sequence. In some instances, the encoded long linker sequence comprises (G4S)n, wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the encoded linker sequence comprises a short linker (SL) sequence. In some instances, the encoded short linker sequence comprises (G4S)n, wherein n=1 to 3 (SEQ ID NO: 21). 
     In some embodiments, the isolated nucleic acid molecules further comprise a sequence encoding a co-stimulatory domain. In some instances, the co-stimulatory domain is a functional signaling domain obtained from a protein selected from the group consisting of OX40, CD2, CD27, CD28, CDS, ICAM-1, LFA-1 (CD11a/CD18), ICOS (CD278), and 4-1BB (CD137), or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. 
     In some embodiments, the isolated nucleic acid molecules further comprise a leader sequence. 
     Also provided herein are isolated polypeptide molecules encoded by any of the previously described nucleic acid molecules. 
     In some embodiments, the encoded anti-tumor antigen binding domain, CD16 domain, or NKG2D domain, or fragment thereof is connected to the TCR extracellular domain by a linker sequence. In some instances, the encoded linker sequence comprises (G4S) n , wherein n=1 to 4 (SEQ ID NO: 19). In some instances, the encoded linker sequence comprises a long linker (LL) sequence. In some instances, the encoded long linker sequence comprises (G4S) n , wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the encoded linker sequence comprises a short linker (SL) sequence. In some instances, the encoded short linker sequence comprises (G4S) n , wherein n=1 to 3 (SEQ ID NO: 21). 
     In some embodiments, the isolated nucleic acid molecules further comprise a sequence encoding a co-stimulatory domain and/or an adaptor molecule such as DNAX. In some instances, the co-stimulatory domain is a functional signaling domain obtained from a protein selected from the group consisting of MHC class 1 molecule, BTLA and a toll-like receptor, as well as DAP10, DAP12, CD30, LIGHT, OX40, GITR, CD2, CD27, CD7, CD28, CDS, ICAM-1, lymphocyte function-associated antigen-1 (LFA-1, also known as CD11a/CD18), NKG2C, ICOS, BAFFR, HVEM, NKG2C, SLAMF7, NKp80, CD160, B7-H3, 4-1BB (CD137), and a ligand that specifically binds with CD83, or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. 
     In some embodiments, the isolated nucleic acid molecules further comprise a leader sequence. 
     Also provided herein are isolated polypeptide molecules encoded by any of the previously described nucleic acid molecules. 
     In some embodiments, the isolated TFP molecules comprise a TCR extracellular domain that comprises an extracellular domain or portion thereof of a protein selected from the group consisting of the alpha or beta chain of the T-cell receptor, CD3 delta, CD3 epsilon, or CD3 gamma, or an amino acid sequence having at least one, two or three modifications but not more than 20, 10 or 5 modifications thereto. 
     In some embodiments, the anti-tumor antigen binding domain, CD16 domain, or NKG2D domain, or fragment thereof is connected to the TCR extracellular domain by a linker sequence. In some instances, the linker region comprises (G4S) n , wherein n=1 to 4 (SEQ ID NO: 19). In some instances, the linker sequence comprises a long linker (LL) sequence. In some instances, the long linker sequence comprises (G4S) n , wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the linker sequence comprises a short linker (SL) sequence. In some instances, the short linker sequence comprises (G4S) n , wherein n=1 to 3 (SEQ ID NO: 21). 
     In some embodiments, the isolated TFP molecules further comprise a sequence encoding a co-stimulatory domain. In other embodiments, the isolated TFP molecules further comprise a sequence encoding an intracellular signaling domain. In yet other embodiments, the isolated TFP molecules further comprise a leader sequence. 
     Also provided herein are vectors that comprise a nucleic acid molecule encoding any of the previously described TFP molecules. In some embodiments, the vector is selected from the group consisting of a DNA, a RNA, a plasmid, a lentivirus vector, adenoviral vector, or a retrovirus vector. In some embodiments, the vector further comprises a promoter. In some embodiments, the vector is an in vitro transcribed vector. In some embodiments, a nucleic acid sequence in the vector further comprises a poly(A) tail. In some embodiments, a nucleic acid sequence in the vector further comprises a 3′UTR. 
     Also provided herein are cells that comprise any of the described vectors. In some embodiments, the cell is a human T-cell. In some embodiments, the cell is a CD8+ or CD4+ T-cell. In other embodiments, the cells further comprise a nucleic acid encoding an inhibitory molecule that comprises a first polypeptide that comprises at least a portion of an inhibitory molecule, associated with a second polypeptide that comprises a positive signal from an intracellular signaling domain. In some instances, the inhibitory molecule comprises a first polypeptide that comprises at least a portion of PD-1 and a second polypeptide comprising a co-stimulatory domain and primary signaling domain. 
     In another aspect, provided herein are isolated TFP molecules that comprise an anti-tumor antigen binding domain, CD16 domain, or NKG2D domain protein or fragment thereof, a TCR extracellular domain, a transmembrane domain, and an intracellular signaling domain, wherein the TFP molecule is capable of functionally interacting with an endogenous TCR complex and/or at least one endogenous TCR polypeptide. 
     In another aspect, provided herein are isolated TFP molecules that comprise an anti-tumor antigen binding domain, CD16 domain, or NKG2D domain protein or fragment thereof, a TCR extracellular domain, a transmembrane domain, and an intracellular signaling domain, wherein the TFP molecule is capable of functionally integrating into an endogenous TCR complex. 
     In another aspect, provided herein are human CD8+ or CD4+ T cells (e.g., a population of cells) that comprises at least two TFP molecules, or a TFP molecule and a PD-1 fusion protein, the TFP molecules comprising a tumor-associated antigen polypeptide or fragment thereof, a TCR extracellular domain, a transmembrane domain, and an intracellular domain, wherein the TFP molecule is capable of functionally interacting with an endogenous TCR complex and/or at least one endogenous TCR polypeptide in, at and/or on the surface of the human CD8+ or CD4+ T-cell. In one embodiment, the one or more TFP molecules and the PD-1 fusion protein are present in the same cell. In another embodiment, the one or more TFP molecules and the PD-1 fusion protein are present in the same population of cells. 
     In another aspect, provided herein are protein complexes that comprise i) a TFP molecule comprising an anti-tumor antigen binding domain, CD16 domain, or NKG2D domain polypeptide or fragment thereof, a TCR extracellular domain, a transmembrane domain, and an intracellular domain; and ii) at least one endogenous TCR complex. 
     In some embodiments, the TCR comprises an extracellular domain or portion thereof of a protein selected from the group consisting of the alpha or beta chain of the T-cell receptor, CD3 delta, CD3 epsilon, or CD3 gamma. In some embodiments, the anti-tumor antigen binding domain, CD16 domain, or NKG2D domain polypeptide or fragment thereof is connected to the TCR extracellular domain by a linker sequence. In some instances, the linker region comprises (G4S) n , wherein n=1 to 4 (SEQ ID NO: 19). In some instances, the linker sequence comprises a long linker (LL) sequence. In some instances, the long linker sequence comprises (G4S) n , wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the linker sequence comprises a short linker (SL) sequence. In some instances, the short linker sequence comprises (G4S) n , wherein n=1 to 3 (SEQ ID NO: 21). 
     In another aspect, provided herein is a population of human CD8+ or CD4+ T cells, wherein the T cells of the population individually or collectively comprise at least two TFP molecules, the TFP molecules comprising an anti-tumor antigen binding domain, CD16 domain, or NKG2D domain polypeptide or fragment thereof, a TCR extracellular domain, a transmembrane domain, and an intracellular domain, wherein the TFP molecule is capable of functionally interacting with an endogenous TCR complex and/or at least one endogenous TCR polypeptide in, at and/or on the surface of the human CD8+ or CD4+ T-cell. 
     In another aspect, provided herein is a population of human CD8+ or CD4+ T cells, wherein the T cells of the population individually or collectively comprise at least two TFP molecules encoded by an isolated nucleic acid molecule provided herein. 
     In another aspect, provided herein are methods of making a cell comprising transducing a T-cell with any of the described vectors or combinations of vectors. In one embodiment, the T cell is transduced with a single vector comprising a TFP described herein and a PD-1 fusion protein. In another embodiment, the T cell is transduced with more than one vector, comprising at least one vector expressing a TFP provided herein and at least one vector expressing a PD-1 fusion protein as provided herein. 
     In another aspect, provided herein are methods of generating a population of RNA-engineered cells that comprise introducing an in vitro transcribed RNA or synthetic RNA into a cell, where the RNA comprises a nucleic acid encoding any of the described TFP molecules and/or the PD-1 fusion proteins. 
     In another aspect, provided herein are methods of providing an anti-tumor immunity in a mammal that comprise administering to the mammal an effective amount of a cell expressing any of the described TFP molecules and PD-1 fusion proteins/switch-receptors. In some embodiments, the cell is an autologous T-cell. In some embodiments, the cell is an allogeneic T-cell. In some embodiments, the mammal is a human. 
     In some embodiments, the mammal has a proliferative disorder. The proliferative disorder may be a cancer, such as a hematological cancer or a solid tumor. In one embodiment, the tumor cells or cells in the tumor microenvironment express PD-L1 or PD-L2. In one embodiment, the mammal is resistant to at least one anti-cancer therapeutic agent. 
     Thus, in another aspect, the engineered T cells comprising the PD-1 fusion proteins and TFPs disclosed herein are useful for treating a proliferative disease such as a cancer or malignancy or a precancerous condition wherein the cancer cells express ligands of PD-1, i.e., PD-L1 or PD-L2. Non-limiting examples include cancers such as lung cancer (Dong et al., Nat Med. 8(8) (2002), 793-800), ovarian cancer (Dong et al., Nat Med. 8(8) (2002), 793-800), melanoma (Dong et al., Nat Med. 8(8) (2002), 793-800), colon cancer (Dong et al., Nat Med. 8(8) (2002), 793-800), gastric cancer (Chen et al., World J Gastroenterol. 9(6) (2003), 1370-1373), renal cell carcinoma (Thompson et al., 104(10) (2005), 2084-91), esophageal carcinoma (Ohigashi et al., 11(8) (2005), 2947-2953), glioma (Wintterle et al., Cancer Res. 63(21) (2003), 7462-7467), urothelial cancer (Nakanishi et al., Cancer Immunol Immunother. 56(8) (2007), 1173-1182), retinoblastoma (Usui et al., Invest Ophthalmol Vis Sci. 47(10) (2006), 4607-4613), breast cancer (Ghebeh et al., Neoplasia 8(3) (2006), 190-198), Non-Hodgkin lymphoma (Xerri et al., Hum Pathol. 39(7) (2008), 1050-1058), pancreatic carcinoma (Geng et al., J Cancer Res Clin Oncol. 134(9) (2008), 1021-1027), Hodgkin&#39;s lymphoma (Yamamoto et al., Blood 111(6) (2008), 3220-3224), myeloma (Liu et al., Blood 110(1) (2007), 296-304), hepatocellular carcinoma (Gao et al., Clin Cancer Res. 15(3) (2009), 971-979), leukemia (Kozako et al., Leukemia 23(2) (2009), 375-382), cervical carcinoma (Karim et al., Clin Cancer Res. 15(20) (2009), 6341-6347), cholangiocarcinoma (Ye et al., J Surg Oncol. 100(6) (2009), 500-504), oral cancer (Malaspina et al., Cancer Immunol Immunother. 60(7) (2011), 965-974), head and neck cancer (Badoual et al., Cancer Res. 73(1) (2013), 128-138), and mesothelioma (Mansfield et al., J Thorac Oncol. 9(7) (2014), 1036-1040). 
     In some embodiments, the cells expressing any of the described TFP molecules are administered in combination with an agent that ameliorates one or more side effects associated with administration of a cell expressing a TFP molecule. In some embodiments, the cells expressing any of the described TFP molecules are administered in combination with an agent that treats the disease associated with PD-1. 
     Also provided herein are any of the described isolated nucleic acid molecules, any of the described isolated polypeptide molecules, any of the described isolated TFPs, any of the described protein complexes, any of the described vectors or any of the described cells for use as a medicament 
     Definitions 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. 
     The term “a” and “an” refers to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. 
     As used herein, “about” can mean plus or minus less than 1 or 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, or greater than 30 percent, depending upon the situation and known or knowable by one skilled in the art. 
     As used herein the specification, “subject” or “subjects” or “individuals” may include, but are not limited to, mammals such as humans or non-human mammals, e.g., domesticated, agricultural or wild, animals, as well as birds, and aquatic animals. “Patients” are subjects suffering from or at risk of developing a disease, disorder or condition or otherwise in need of the compositions and methods provided herein. 
     As used herein, “treating” or “treatment” refers to any indicia of success in the treatment or amelioration of the disease or condition. Treating can include, for example, reducing, delaying or alleviating the severity of one or more symptoms of the disease or condition, or it can include reducing the frequency with which symptoms of a disease, defect, disorder, or adverse condition, and the like, are experienced by a patient. As used herein, “treat or prevent” is sometimes used herein to refer to a method that results in some level of treatment or amelioration of the disease or condition, and contemplates a range of results directed to that end, including but not restricted to prevention of the condition entirely. 
     As used herein, “preventing” refers to the prevention of the disease or condition, e.g., tumor formation, in the patient. For example, if an individual at risk of developing a tumor or other form of cancer is treated with the methods of the present invention and does not later develop the tumor or other form of cancer, then the disease has been prevented, at least over a period of time, in that individual. 
     As used herein, a “therapeutically effective amount” is the amount of a composition or an active component thereof sufficient to provide a beneficial effect or to otherwise reduce a detrimental non-beneficial event to the individual to whom the composition is administered. By “therapeutically effective dose” herein is meant a dose that produces one or more desired or desirable (e.g., beneficial) effects for which it is administered, such administration occurring one or more times over a given period of time. The exact dose will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques (see, e.g. Lieberman, Pharmaceutical Dosage Forms (vols. 1-3, 1992); Lloyd,  The Art, Science and Technology of Pharmaceutical Compounding  (1999); and Pickar, Dosage Calculations (1999)) 
     As used herein, the term “fusion protein” relates to a protein which is made of polypeptide parts from different sources. Accordingly, it may be also understood as a chimeric protein. In the context of the PD-1 fusion proteins described herein, the term “fusion protein” is used interchangeably with the term “switch-receptor.” Usually, fusion proteins are proteins created through the joining of two or more genes (or preferably cDNAs) that originally coded for separate proteins. Translation of this fusion gene (or fusion cDNA) results in a single polypeptide, preferably with functional properties derived from each of the original proteins. Recombinant fusion proteins are created artificially by recombinant DNA technology for use in biological research or therapeutics. Further details to the production of the fusion protein of the present invention are described herein below. 
     In the context of the present invention, the terms “polypeptide”, “peptide” and “protein” are used interchangeably to refer to a polymer of amino acid residues. The term also applies to amino acid polymers in which one or more amino acid residues is an artificial chemical mimetic or a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers. Accordingly, in the context of the present invention, the term “polypeptide” relates to a molecule which comprises or consists of chains of amino acid monomers linked by peptide (amide) bonds. Peptide bonds are covalent chemical bonds which are formed when the carboxyl group of one amino acid reacts with the amino group of another. Herein a “polypeptide” is not restricted to a molecule with a defined length. Thus, herein the term “polypeptide” relates to a peptide, an oligopeptide, a protein, or a polypeptide which encompasses amino acid chains, wherein the amino acid residues are linked by covalent peptide bonds. However, herein the term “polypeptide” also encompasses peptidomimetics of such proteins/polypeptides wherein amino acid(s) and/or peptide bond(s) have been replaced by functional analogs. The term polypeptide also refers to, and does not exclude, modifications of the polypeptide, e.g., glycosylation, acetylation, phosphorylation and the like. Such modifications are well described in the art. 
     As used herein, a “T-cell receptor (TCR) fusion protein” or “TFP” includes a recombinant polypeptide derived from the various polypeptides comprising the TCR that is generally capable of i) binding to a surface antigen on target cells and ii) interacting with other polypeptide components of the intact TCR complex, typically when co-located in or on the surface of a T-cell. 
     As used herein, the term “PD-1” refers Programmed Cell Death Protein 1, also known as CD279 (cluster of differentiation 279), an inhibitory cell surface receptor expressed on T cells and pro-B cells. involved in the regulation of T-cell function during immunity and tolerance. Upon ligand binding, PD-1 inhibits T-cell effector functions in an antigen-specific manner. It functions as a possible cell death inducer, in association with other factors. In humans, PD-1 is encoded by the PDCD1 gene. PD-1 is known to bind to two ligands, PD-L1 and PD-L2. PD-1 and its ligands play an important role in down regulating the immune system by preventing the activation of T cells, which in turn reduces autoimmunity and promotes self-tolerance. The inhibitory effect of PD-1 is accomplished through a dual mechanism of promoting apoptosis (programmed cell death) in antigen-specific T cells in lymph nodes while simultaneously reducing apoptosis in regulatory T cells (suppressor T cells). 
     The human and murine amino acid and nucleic acid sequences can be found in a public database, such as GenBank, UniProt and Swiss-Prot. For example, the human PD-1 sequence corresponds to UniProt Accession No. Q02242 and has the sequence: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 14) 
               
               
                 MQIPQAPWPVVWAVLQLGWRPGWFLDSPDRPWNPPTFSPALLVVTEGDNA 
               
               
                   
               
               
                 TFTCSFSNTSESFVLNWYRMSPSNQTDKLAAFPEDRSQPGQDCRFRVTQL 
               
               
                   
               
               
                 PNGRDFHMSVVRARRNDSGTYLCGAISLAPKAQIKESLRAELRVTERRAE 
               
               
                   
               
               
                 VPTAHPSPSPRPAGQFQTLVVGVVGGLLGSLVLLVWVLAVICSRAARGTI 
               
               
                   
               
               
                 GARRTGQPLKEDPSAVPVFSVDYGELDFQWREKTPEPPVPCVPEQTEYAT 
               
               
                   
               
               
                 IVFPSGMGTSSPARRGSADGPRSAQPLRPEDGHCSWPL. 
               
            
           
         
       
     
     The term “PD-1 fusion protein” or “PD-1” switch receptor, as used herein, refers to the described PD-1 fusion proteins that receive an inhibitory signal by binding to PD-L1 or PD-L2, and transform (i.e., “switch”) the signal via the co-stimulatory domain of the fusion protein into an activating signal. 
     The term “anti-tumor effect” refers to a biological effect which can be manifested by various means, including but not limited to, e.g., a decrease in tumor volume, a decrease in the number of tumor cells, a decrease in the number of metastases, an increase in life expectancy, decrease in tumor cell proliferation, decrease in tumor cell survival, or amelioration of various physiological symptoms associated with the cancerous condition. An “anti-tumor effect” can also be manifested by the ability of the peptides, polynucleotides, cells and antibodies of the invention in prevention of the occurrence of tumor in the first place. 
     The term “autologous” refers to any material derived from the same individual to whom it is later to be re-introduced into the individual. In one embodiment, the TFP T cells and PD-1 switch cells disclosed herein are autologous to the recipient of the T cells. 
     The term “allogenic” or “allogeneic” refers to any material derived from a different animal of the same species or different patient as the individual to whom the material is introduced. Two or more individuals are said to be allogeneic to one another when the genes at one or more loci are not identical. In some aspects, allogeneic material from individuals of the same species may be sufficiently unlike genetically to interact antigenically. In one embodiment, the TFP T cells and PD-1 switch cells disclosed herein are allogenic to the recipient of the T cells. 
     The term “xenogenic” or “xenogeneic” refers to a graft derived from an animal of a different species. 
     The term “cancer” refers to a disease characterized by the rapid and uncontrolled growth of aberrant cells. Cancer cells can spread locally or through the bloodstream and lymphatic system to other parts of the body. Examples of various cancers are described herein and include, but are not limited to, prostate cancer, breast cancer, melanoma, sarcoma, colorectal cancer, pancreatic cancer, uterine cancer, ovarian cancer, stomach cancer, gastric cancer, small cell lung cancer, non-small cell lung cancer, bladder cancer, cholangiocarcinoma, squamous cell lung cancer, mesothelioma, adrenocortico carcinoma, esophageal cancer, head &amp; neck cancer, liver cancer, nasopharyngeal carcinoma, neuroepithelial cancer, adenoid cystic carcinoma, thymoma, chronic lymphocytic leukemia, glioma, glioblastoma multiforme, neuroblastoma, papillary renal cell carcinoma, mantle cell lymphoma, lymphoblastic leukemia, acute myeloid leukemia, and the like. 
     The term “conservative sequence modifications” refers to amino acid modifications that do not significantly affect or alter the binding characteristics of the antibody or antibody fragment containing the amino acid sequence. Such conservative modifications include amino acid substitutions, additions and deletions. Modifications can be introduced into an antibody or antibody fragment of the invention by standard techniques known in the art, such as site-directed mutagenesis and PCR-mediated mutagenesis. Conservative amino acid substitutions are ones in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine, tryptophan), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Thus, one or more amino acid residues within a TFP of the invention can be replaced with other amino acid residues from the same side chain family and the altered TFP can be tested using the functional assays described herein. 
     The term “stimulation” refers to a primary response induced by binding of a stimulatory domain or stimulatory molecule (e.g., a TCR/CD3 complex) with its cognate ligand thereby mediating a signal transduction event, such as, but not limited to, signal transduction via the TCR/CD3 complex. Stimulation can mediate altered expression of certain molecules, and/or reorganization of cytoskeletal structures, and the like. 
     The term “stimulatory molecule” or “stimulatory domain” refers to a molecule or portion thereof expressed by a T-cell that provides the primary cytoplasmic signaling sequence(s) that regulate primary activation of the TCR complex in a stimulatory way for at least some aspect of the T-cell signaling pathway. In one aspect, the primary signal is initiated by, for instance, binding of a TCR/CD3 complex with an MHC molecule loaded with peptide, and which leads to mediation of a T-cell response, including, but not limited to, proliferation, activation, differentiation, and the like. A primary cytoplasmic signaling sequence (also referred to as a “primary signaling domain”) that acts in a stimulatory manner may contain a signaling motif which is known as immunoreceptor tyrosine-based activation motif or “ITAM”. Examples of an ITAM containing primary cytoplasmic signaling sequence that is of particular use in the invention includes, but is not limited to, those derived from TCR zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, CD278 (also known as “ICOS”) and CD66d. 
     The term “antigen presenting cell” or “APC” refers to an immune system cell such as an accessory cell (e.g., a B-cell, a dendritic cell, and the like) that displays a foreign antigen complexed with major histocompatibility complexes (MHC&#39;s) on its surface. T cells may recognize these complexes using their T-cell receptors (TCRs). APCs process antigens and present them to T cells. 
     An “intracellular signaling domain,” as the term is used herein, refers to an intracellular portion of a molecule. The intracellular signaling domain generates a signal that promotes an immune effector function of the TFP containing cell, e.g., a TFP-expressing T-cell. Examples of immune effector function, e.g., in a TFP-expressing T-cell, include cytolytic activity and T helper cell activity, including the secretion of cytokines. In an embodiment, the intracellular signaling domain can comprise a primary intracellular signaling domain. Exemplary primary intracellular signaling domains include those derived from the molecules responsible for primary stimulation, or antigen dependent simulation. In an embodiment, the intracellular signaling domain can comprise a co-stimulatory intracellular domain. Exemplary co-stimulatory intracellular signaling domains include those derived from molecules responsible for co-stimulatory signals, or antigen independent stimulation. 
     A primary intracellular signaling domain can comprise an ITAM (“immunoreceptor tyrosine-based activation motif”). Examples of ITAM containing primary cytoplasmic signaling sequences include, but are not limited to, those derived from CD3 zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, and CD66d DAP10 and DAP12. 
     The term “co-stimulatory molecule” refers to the cognate binding partner on a T-cell that specifically binds with a co-stimulatory ligand, thereby mediating a co-stimulatory response by the T-cell, such as, but not limited to, proliferation. Co-stimulatory molecules are cell surface molecules other than antigen receptors or their ligands that are required for an efficient immune response. Co-stimulatory molecules include, but are not limited to an MHC class 1 molecule, BTLA and a Toll ligand receptor, as well as DAP10, DAP12, CD30, LIGHT, OX40, GITR, CD2, CD27, CD7, CD28, CDS, ICAM-1, lymphocyte function-associated antigen-1 (LFA-1, also known as CD11a/CD18), NKG2C, ICOS, BAFFR, HVEM, NKG2C, SLAMF7, NKp80, CD160, B7-H3, 4-1BB (CD137), and a ligand that specifically binds with CD83. A co-stimulatory intracellular signaling domain can be the intracellular portion of a co-stimulatory molecule. A co-stimulatory molecule can be represented in the following protein families: TNF receptor proteins, Immunoglobulin-like proteins, cytokine receptors, integrins, signaling lymphocytic activation molecules (SLAM proteins), and activating NK cell receptors. The intracellular signaling domain can comprise the entire intracellular portion, or the entire native intracellular signaling domain, of the molecule from which it is derived, or a functional fragment thereof. The term “4-1BB” refers to a member of the TNFR superfamily with an amino acid sequence provided as GenBank Acc. No. AAA62478.2, or the equivalent residues from a non-human species, e.g., mouse, rodent, monkey, ape and the like; and a “4-1BB co-stimulatory domain” is defined as amino acid residues 214-255 of GenBank Acc. No. AAA62478.2, or equivalent residues from non-human species, e.g., mouse, rodent, monkey, ape and the like. 
     The term “encoding” refers to the inherent property of specific sequences of nucleotides in a polynucleotide, such as a gene, a cDNA, or an mRNA, to serve as templates for synthesis of other polymers and macromolecules in biological processes having either a defined sequence of nucleotides (e.g., rRNA, tRNA and mRNA) or a defined sequence of amino acids and the biological properties resulting therefrom. Thus, a gene, cDNA, or RNA, encodes a protein if transcription and translation of mRNA corresponding to that gene produces the protein in a cell or other biological system. Both the coding strand, the nucleotide sequence of which is identical to the mRNA sequence and is usually provided in sequence listings, and the non-coding strand, used as the template for transcription of a gene or cDNA, can be referred to as encoding the protein or other product of that gene or cDNA. 
     Unless otherwise specified, a “nucleotide sequence encoding an amino acid sequence” includes all nucleotide sequences that are degenerate versions of each other and that encode the same amino acid sequence. The phrase nucleotide sequence that encodes a protein or an RNA may also include introns to the extent that the nucleotide sequence encoding the protein may in some version contain one or more introns. 
     The term “effective amount” or “therapeutically effective amount” are used interchangeably herein, and refer to an amount of a compound, formulation, material, or composition, as described herein effective to achieve a particular biological or therapeutic result. 
     The term “endogenous” refers to any material from or produced inside an organism, cell, tissue or system. 
     The term “exogenous” refers to any material introduced from or produced outside an organism, cell, tissue or system. 
     The term “expression” refers to the transcription and/or translation of a particular nucleotide sequence driven by a promoter. 
     The term “transfer vector” refers to a composition of matter which comprises an isolated nucleic acid and which can be used to deliver the isolated nucleic acid to the interior of a cell. Numerous vectors are known in the art including, but not limited to, linear polynucleotides, polynucleotides associated with ionic or amphiphilic compounds, plasmids, and viruses. Thus, the term “transfer vector” includes an autonomously replicating plasmid or a virus. The term should also be construed to further include non-plasmid and non-viral compounds which facilitate transfer of nucleic acid into cells, such as, for example, a polylysine compound, liposome, and the like. Examples of viral transfer vectors include, but are not limited to, adenoviral vectors, adeno-associated virus vectors, retroviral vectors, lentiviral vectors, and the like. 
     The term “expression vector” refers to a vector comprising a recombinant polynucleotide comprising expression control sequences operatively linked to a nucleotide sequence to be expressed. An expression vector comprises sufficient cis-acting elements for expression; other elements for expression can be supplied by the host cell or in an in vitro expression system. Expression vectors include all those known in the art, including cosmids, plasmids (e.g., naked or contained in liposomes) and viruses (e.g., lentiviruses, retroviruses, adenoviruses, and adeno-associated viruses) that incorporate the recombinant polynucleotide. 
     The term “lentivirus” refers to a genus of the Retroviridae family. Lentiviruses are unique among the retroviruses in being able to infect non-dividing cells; they can deliver a significant amount of genetic information into the DNA of the host cell, so they are one of the most efficient methods of a gene delivery vector. HIV, SIV, and FIV are all examples of lentiviruses. 
     The term “lentiviral vector” refers to a vector derived from at least a portion of a lentivirus genome, including especially a self-inactivating lentiviral vector as provided in Milone et al., Mol. Ther. 17(8): 1453-1464 (2009). Other examples of lentivirus vectors that may be used in the clinic, include but are not limited to, e.g., the LENTIVECTOR™ gene delivery technology from Oxford BioMedica, the LENTIMAX™ vector system from Lentigen, and the like. Nonclinical types of lentiviral vectors are also available and would be known to one skilled in the art. 
     The term “homologous” or “identity” refers to the subunit sequence identity between two polymeric molecules, e.g., between two nucleic acid molecules, such as, two DNA molecules or two RNA molecules, or between two polypeptide molecules. When a subunit position in both of the two molecules is occupied by the same monomeric subunit; e.g., if a position in each of two DNA molecules is occupied by adenine, then they are homologous or identical at that position. The homology between two sequences is a direct function of the number of matching or homologous positions; e.g., if half (e.g., five positions in a polymer ten subunits in length) of the positions in two sequences are homologous, the two sequences are 50% homologous; if 90% of the positions (e.g., 9 of 10), are matched or homologous, the two sequences are 90% homologous. 
     “Humanized” forms of non-human (e.g., murine) antibodies are chimeric immunoglobulins, immunoglobulin chains or fragments thereof (such as Fv, Fab, Fab′, F(ab′) 2  or other antigen-binding subsequences of antibodies) which contain minimal sequence derived from non-human immunoglobulin. For the most part, humanized antibodies and antibody fragments thereof are human immunoglobulins (recipient antibody or antibody fragment) in which residues from a complementary-determining region (CDR) of the recipient are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat or rabbit having the desired specificity, affinity, and capacity. In some instances, Fv framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, a humanized antibody/antibody fragment can comprise residues which are found neither in the recipient antibody nor in the imported CDR or framework sequences. These modifications can further refine and optimize antibody or antibody fragment performance. In general, the humanized antibody or antibody fragment thereof will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or a significant portion of the FR regions are those of a human immunoglobulin sequence. The humanized antibody or antibody fragment can also comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin. For further details, see Jones et al., Nature, 321: 522-525, 1986; Reichmann et al., Nature, 332: 323-329, 1988; Presta, Curr. Op. Struct. Biol., 2: 593-596, 1992. 
     “Human” or “fully human” refers to an immunoglobulin, such as an antibody or antibody fragment, where the whole molecule is of human origin or consists of an amino acid sequence identical to a human form of the antibody or immunoglobulin. 
     The term “isolated” means altered or removed from the natural state. For example, a nucleic acid or a peptide naturally present in a living animal is not “isolated,” but the same nucleic acid or peptide partially or completely separated from the coexisting materials of its natural state is “isolated.” An isolated nucleic acid or protein can exist in substantially purified form, or can exist in a non-native environment such as, for example, a host cell. 
     In the context of the present invention, the following abbreviations for the commonly occurring nucleic acid bases are used. “A” refers to adenosine, “C” refers to cytosine, “G” refers to guanosine, “T” refers to thymidine, and “U” refers to uridine. 
     The term “operably linked” or “transcriptional control” refers to functional linkage between a regulatory sequence and a heterologous nucleic acid sequence resulting in expression of the latter. For example, a first nucleic acid sequence is operably linked with a second nucleic acid sequence when the first nucleic acid sequence is placed in a functional relationship with the second nucleic acid sequence. For instance, a promoter is operably linked to a coding sequence if the promoter affects the transcription or expression of the coding sequence. Operably linked DNA sequences can be contiguous with each other and, e.g., where necessary to join two protein coding regions, are in the same reading frame. 
     The term “parenteral” administration of an immunogenic composition includes, e.g., subcutaneous (s.c.), intravenous (i.v.), intramuscular (i.m.), or intrasternal injection, intratumoral, or infusion techniques. 
     The term “nucleic acid” or “polynucleotide” refers to deoxyribonucleic acids (DNA) or ribonucleic acids (RNA) and polymers thereof in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acids containing known analogues of natural nucleotides that have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions), alleles, orthologs, SNPs, and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues (Batzer et al., Nucleic Acid Res. 19:5081 (1991); Ohtsuka et al., J. Biol. Chem. 260:2605-2608 (1985); and Rossolini et al., Mol. Cell. Probes 8:91-98 (1994)). 
     The terms “peptide,” “polypeptide,” and “protein” are used interchangeably, and refer to a compound comprised of amino acid residues covalently linked by peptide bonds. A protein or peptide must contain at least two amino acids, and no limitation is placed on the maximum number of amino acids that can comprise a protein&#39;s or peptide&#39;s sequence. Polypeptides include any peptide or protein comprising two or more amino acids joined to each other by peptide bonds. As used herein, the term refers to both short chains, which also commonly are referred to in the art as peptides, oligopeptides and oligomers, for example, and to longer chains, which generally are referred to in the art as proteins, of which there are many types. “Polypeptides” include, for example, biologically active fragments, substantially homologous polypeptides, oligopeptides, homodimers, heterodimers, variants of polypeptides, modified polypeptides, derivatives, analogs, fusion proteins, among others. A polypeptide includes a natural peptide, a recombinant peptide, or a combination thereof. 
     The term “promoter” refers to a DNA sequence recognized by the transcription machinery of the cell, or introduced synthetic machinery, required to initiate the specific transcription of a polynucleotide sequence. 
     The term “promoter/regulatory sequence” refers to a nucleic acid sequence which is required for expression of a gene product operably linked to the promoter/regulatory sequence. In some instances, this sequence may be the core promoter sequence and in other instances, this sequence may also include an enhancer sequence and other regulatory elements which are required for expression of the gene product. The promoter/regulatory sequence may, for example, be one which expresses the gene product in a tissue specific manner. 
     The term “constitutive” promoter refers to a nucleotide sequence which, when operably linked with a polynucleotide which encodes or specifies a gene product, causes the gene product to be produced in a cell under most or all physiological conditions of the cell. 
     The term “inducible” promoter refers to a nucleotide sequence which, when operably linked with a polynucleotide which encodes or specifies a gene product, causes the gene product to be produced in a cell substantially only when an inducer which corresponds to the promoter is present in the cell. 
     The term “tissue-specific” promoter refers to a nucleotide sequence which, when operably linked with a polynucleotide encodes or specified by a gene, causes the gene product to be produced in a cell substantially only if the cell is a cell of the tissue type corresponding to the promoter. 
     The terms “linker” and “flexible polypeptide linker” as used in the context of a scFv refers to a peptide linker that consists of amino acids such as glycine and/or serine residues used alone or in combination, to link variable heavy and variable light chain regions together. In one embodiment, the flexible polypeptide linker is a Gly/Ser linker and comprises the amino acid sequence (Gly-Gly-Gly-Ser) n , where n is a positive integer equal to or greater than 1 (SEQ ID NO: 22). For example, n=1, n=2, n=3, n=4, n=5, n=6, n=7, n=8, n=9 and n=10. In one embodiment, the flexible polypeptide linkers include, but are not limited to, (Gly4Ser) 4  (SEQ ID NO: 23) or (Gly4Ser) 3  (SEQ ID NO: 24). In another embodiment, the linkers include multiple repeats of (Gly2Ser), (GlySer) or (Gly 3 Ser) (SEQ ID NO: 22). Also included within the scope of the invention are linkers described in WO2012/138475 (incorporated herein by reference). In some instances, the linker sequence comprises a long linker (LL) sequence. In some instances, the long linker sequence comprises (G4S) n , wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the linker sequence comprises a short linker (SL) sequence. In some instances, the short linker sequence comprises (G4S) n , wherein n=1 to 3 (SEQ ID NO: 21). 
     As used herein, a 5′ cap (also termed an RNA cap, an RNA 7-methylguanosine cap or an RNA m7G cap) is a modified guanine nucleotide that has been added to the “front” or 5′ end of a eukaryotic messenger RNA shortly after the start of transcription. The 5′ cap consists of a terminal group which is linked to the first transcribed nucleotide. Its presence is critical for recognition by the ribosome and protection from RNases. Cap addition is coupled to transcription, and occurs co-transcriptionally, such that each influences the other. Shortly after the start of transcription, the 5′ end of the mRNA being synthesized is bound by a cap-synthesizing complex associated with RNA polymerase. This enzymatic complex catalyzes the chemical reactions that are required for mRNA capping. Synthesis proceeds as a multi-step biochemical reaction. The capping moiety can be modified to modulate functionality of mRNA such as its stability or efficiency of translation. 
     As used herein, “in vitro transcribed RNA” refers to RNA, preferably mRNA, which has been synthesized in vitro. Generally, the in vitro transcribed RNA is generated from an in vitro transcription vector. The in vitro transcription vector comprises a template that is used to generate the in vitro transcribed RNA. 
     As used herein, a “poly(A)” is a series of adenosines attached by polyadenylation to the mRNA. In the preferred embodiment of a construct for transient expression, the polyA is between 50 and 5000 (SEQ ID NO: 25), preferably greater than 64, more preferably greater than 100, most preferably greater than 300 or 400. Poly(A) sequences can be modified chemically or enzymatically to modulate mRNA functionality such as localization, stability or efficiency of translation. 
     As used herein, “polyadenylation” refers to the covalent linkage of a polyadenylyl moiety, or its modified variant, to a messenger RNA molecule. In eukaryotic organisms, most messenger RNA (mRNA) molecules are polyadenylated at the 3′ end. The 3′ poly(A) tail is a long sequence of adenine nucleotides (often several hundred) added to the pre-mRNA through the action of an enzyme, polyadenylate polymerase. In higher eukaryotes, the poly(A) tail is added onto transcripts that contain a specific sequence, the polyadenylation signal. The poly(A) tail and the protein bound to it aid in protecting mRNA from degradation by exonucleases. Polyadenylation is also important for transcription termination, export of the mRNA from the nucleus, and translation. Polyadenylation occurs in the nucleus immediately after transcription of DNA into RNA, but additionally can also occur later in the cytoplasm. After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. The cleavage site is usually characterized by the presence of the base sequence AAUAAA near the cleavage site. After the mRNA has been cleaved, adenosine residues are added to the free 3′ end at the cleavage site. 
     As used herein, “transient” refers to expression of a non-integrated transgene for a period of hours, days or weeks, wherein the period of time of expression is less than the period of time for expression of the gene if integrated into the genome or contained within a stable plasmid replicon in the host cell. 
     The term “signal transduction pathway” refers to the biochemical relationship between a variety of signal transduction molecules that play a role in the transmission of a signal from one portion of a cell to another portion of a cell. The phrase “cell surface receptor” includes molecules and complexes of molecules capable of receiving a signal and transmitting signal across the membrane of a cell. 
     The term “subject” is intended to include living organisms in which an immune response can be elicited (e.g., mammals, human). 
     The term, a “substantially purified” cell refers to a cell that is essentially free of other cell types. A substantially purified cell also refers to a cell which has been separated from other cell types with which it is normally associated in its naturally occurring state. In some instances, a population of substantially purified cells refers to a homogenous population of cells. In other instances, this term refers simply to cell that have been separated from the cells with which they are naturally associated in their natural state. In some aspects, the cells are cultured in vitro. In other aspects, the cells are not cultured in vitro. 
     The term “therapeutic” as used herein means a treatment. A therapeutic effect is obtained by reduction, suppression, remission, or eradication of a disease state. 
     The term “prophylaxis” as used herein means the prevention of or protective treatment for a disease or disease state. 
     In the context of the present invention, “PD-1 ligand”, “PD-L1,” and “PD-L2” refer to proteins for which PD-1 has binding affinity. In some embodiments, the PD-1 protein, or binding fragment thereof (such as the extracellular domain of the PD-1 protein), is characterized by the ability to bind the natural ligands of human PD-1, i.e., human PD-L1 (also known as CD274, UniProt Accession No. Q9NZQ7) and/or human PD-L2 (also known as CD273, UniProt Accession No. Q9BQ51) with the same (i.e. equal), enhanced or reduced (i.e. diminished) affinity as compared to the natural PD-1 protein. 
     In certain aspects, the PD-1 ligands of the present invention are derived from cancers including, but not limited to, lung cancer, ovarian cancer, melanoma, colon cancer, gastric cancer, renal cell carcinoma, esophageal carcinoma, glioma, urothelial cancer, retinoblastoma, breast cancer, Non-Hodgkin lymphoma, pancreatic carcinoma, Hodgkin&#39;s lymphoma, myeloma, hepatocellular carcinoma, leukemia, cervical carcinoma, cholangiocarcinoma, oral cancer, head and neck cancer, or mesothelioma. 
     The term “transfected” or “transformed” or “transduced” refers to a process by which exogenous nucleic acid is transferred or introduced into the host cell. A “transfected” or “transformed” or “transduced” cell is one which has been transfected, transformed or transduced with exogenous nucleic acid. The cell includes the primary subject cell and its progeny. 
     The term “specifically binds,” refers to an antibody, an antibody fragment or a specific ligand, which recognizes and binds a cognate binding partner (e.g., PD-1 ligand) present in a sample, but which does not necessarily and substantially recognize or bind other molecules in the sample. 
     Ranges: throughout this disclosure, various aspects of the invention can be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 2.7, 3, 4, 5, 5.3, and 6. As another example, a range such as 95-99% identity, includes something with 95%, 96%, 97%, 98% or 99% identity, and includes subranges such as 96-99%, 96-98%, 96-97%, 97-99%, 97-98% and 98-99% identity. This applies regardless of the breadth of the range. 
     DESCRIPTION 
     Provided herein are compositions of matter and methods of use for the treatment of a disease such as cancer, using T-cell receptor (TCR) fusion proteins. As used herein, a “T-cell receptor (TCR) fusion protein” or “TFP” includes a recombinant polypeptide derived from the various polypeptides comprising the TCR that is generally capable of i) binding to a surface antigen, e.g., a tumor associated antigen, on target cells and ii) interacting with other polypeptide components of the intact TCR complex, typically when co-located in or on the surface of a T-cell. As provided herein, TFPs provide substantial benefits as compared to Chimeric Antigen Receptors. The term “Chimeric Antigen Receptor” or alternatively a “CAR” refers to a recombinant polypeptide comprising an extracellular antigen binding domain in the form of a scFv, a transmembrane domain, and cytoplasmic signaling domains (also referred to herein as “an intracellular signaling domains”) comprising a functional signaling domain derived from a stimulatory molecule as defined below. Generally, the central intracellular signaling domain of a CAR is derived from the CD3 zeta chain that is normally found associated with the TCR complex. The CD3 zeta signaling domain can be fused with one or more functional signaling domains derived from at least one co-stimulatory molecule such as 4-1BB (i.e., CD137), CD27 and/or CD28. 
     T-Cell Receptor (TCR) Fusion Proteins (TFP) 
     The present invention encompasses recombinant DNA constructs encoding TFPs and PD-1 fusion proteins, wherein the TFP in one aspect comprises an antibody fragment that binds specifically to one or more tumor associated antigens (“TAA”), e.g., a human TAA, wherein the sequence of the antibody fragment is contiguous with and in the same reading frame as a nucleic acid sequence encoding a TCR subunit or portion thereof. The TFPs provided herein are able to associate with one or more endogenous (or alternatively, one or more exogenous, or a combination of endogenous and exogenous) TCR subunits in order to form a functional TCR complex. In another aspect, the TFP comprises a CD16 fragment that binds specifically to the Tc region of an IgG1 or IgG4 antibody. 
     In one aspect, the TFP of the invention comprises a target-specific binding element otherwise referred to as an antigen binding domain. The choice of moiety depends upon the type and number of target antigen that define the surface of a target cell. For example, the antigen binding domain may be chosen to recognize a target antigen that acts as a cell surface marker on target cells associated with a particular disease state. Thus, examples of cell surface markers that may act as target antigens for the antigen binding domain in a TFP of the invention include those associated with viral, bacterial and parasitic infections; autoimmune diseases; and cancerous diseases (e.g., malignant diseases). 
     In one aspect, the TFP-mediated T-cell response can be directed to an antigen of interest by way of engineering an antigen-binding domain into the TFP that specifically binds a desired antigen. 
     In one embodiment, the TFP construct of the present invention further comprise a DNAX expression cassette. 
     The antigen binding domain can be any domain that binds to the antigen including but not limited to a monoclonal antibody, a polyclonal antibody, a recombinant antibody, a human antibody, a humanized antibody, and a functional fragment thereof, including but not limited to a single-domain antibody such as a heavy chain variable domain (V H ), a light chain variable domain (VL) and a variable domain (V HH ) of a camelid derived nanobody, and to an alternative scaffold known in the art to function as antigen binding domain, such as a recombinant fibronectin domain, anticalin, DARPIN and the like. Likewise, a natural or synthetic ligand specifically recognizing and binding the target antigen can be used as antigen binding domain for the TFP. In some instances, it is beneficial for the antigen binding domain to be derived from the same species in which the TFP will ultimately be used in. For example, for use in humans, it may be beneficial for the antigen binding domain of the TFP to comprise human or humanized residues for the antigen binding domain of an antibody or antibody fragment. 
     Thus, in one aspect, the antigen-binding domain comprises a humanized or human antibody or an antibody fragment, or a murine antibody or antibody fragment. In one embodiment, the humanized or human anti-TAA binding domain comprises one or more (e.g., all three) light chain complementary determining region 1 (LC CDR1), light chain complementary determining region 2 (LC CDR2), and light chain complementary determining region 3 (LC CDR3) of a humanized or human anti-TAA binding domain described herein, and/or one or more (e.g., all three) heavy chain complementary determining region 1 (HC CDR1), heavy chain complementary determining region 2 (HC CDR2), and heavy chain complementary determining region 3 (HC CDR3) of a humanized or human anti-TAA binding domain described herein, e.g., a humanized or human anti-TAA binding domain comprising one or more, e.g., all three, LC CDRs and one or more, e.g., all three, HC CDRs. In one embodiment, the humanized or human anti-TAA binding domain comprises one or more (e.g., all three) heavy chain complementary determining region 1 (HC CDR1), heavy chain complementary determining region 2 (HC CDR2), and heavy chain complementary determining region 3 (HC CDR3) of a humanized or human anti-TAA binding domain described herein, e.g., the humanized or human anti-tumor-associated antigen binding domain has two variable heavy chain regions, each comprising a HC CDR1, a HC CDR2 and a HC CDR3 described herein. In one embodiment, the humanized or human anti-tumor-associated antigen binding domain comprises a humanized or human light chain variable region described herein and/or a humanized or human heavy chain variable region described herein. In one embodiment, the humanized or human anti-tumor-associated antigen binding domain comprises a humanized heavy chain variable region described herein, e.g., at least two humanized or human heavy chain variable regions described herein. In one embodiment, the anti-tumor-associated antigen binding domain is a scFv comprising a light chain and a heavy chain of an amino acid sequence provided herein. In an embodiment, the anti-tumor-associated antigen binding domain (e.g., an scFv or V H H nb) comprises: a light chain variable region comprising an amino acid sequence having at least one, two or three modifications (e.g., substitutions) but not more than 30, 20 or 10 modifications (e.g., substitutions) of an amino acid sequence of a light chain variable region provided herein, or a sequence with 95-99% identity with an amino acid sequence provided herein; and/or a heavy chain variable region comprising an amino acid sequence having at least one, two or three modifications (e.g., substitutions) but not more than 30, 20 or 10 modifications (e.g., substitutions) of an amino acid sequence of a heavy chain variable region provided herein, or a sequence with 95-99% identity to an amino acid sequence provided herein. In one embodiment, the humanized or human anti-tumor-associated antigen binding domain is a scFv, and a light chain variable region comprising an amino acid sequence described herein, is attached to a heavy chain variable region comprising an amino acid sequence described herein, via a linker, e.g., a linker described herein. In one embodiment, the humanized anti-tumor-associated antigen binding domain includes a (Gly 4 -Ser) n  linker, wherein n is 1, 2, 3, 4, 5, or 6 (SEQ ID NO: 26), preferably 3 or 4. The light chain variable region and heavy chain variable region of a scFv can be, e.g., in any of the following orientations: light chain variable region-linker-heavy chain variable region or heavy chain variable region-linker-light chain variable region. In some instances, the linker sequence comprises a long linker (LL) sequence. In some instances, the long linker sequence comprises (G4S) n , wherein n=2 to 4 (SEQ ID NO: 20). In some instances, the linker sequence comprises a short linker (SL) sequence. In some instances, the short linker sequence comprises (G4S) n , wherein n=1 to 3 (SEQ ID NO: 21). 
     Extracellular Domain 
     The extracellular domain may be derived either from a natural or from a recombinant source. Where the source is natural, the domain may be derived from any protein, but in particular a membrane-bound or transmembrane protein. In one aspect, the extracellular domain is capable of associating with the transmembrane domain. An extracellular domain of particular use in this invention may include at least the extracellular region(s) of e.g., the alpha, beta or zeta chain of the T-cell receptor, or CD3 epsilon, CD3 gamma, or CD3 delta, or in alternative embodiments, CD28, CD45, CD4, CD5, CD8, CD9, CD16, CD22, CD33, CD37, CD64, CD80, CD86, CD134, CD137, CD154. 
     Transmembrane Domain 
     In general, a TFP sequence contains an extracellular domain and a transmembrane domain encoded by a single genomic sequence. In alternative embodiments, a TFP can be designed to comprise a transmembrane domain that is heterologous to the extracellular domain of the TFP. A transmembrane domain can include one or more additional amino acids adjacent to the transmembrane region, e.g., one or more amino acid associated with the extracellular region of the protein from which the transmembrane was derived (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or up to 15 amino acids of the extracellular region) and/or one or more additional amino acids associated with the intracellular region of the protein from which the transmembrane protein is derived (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or up to 15 amino acids of the intracellular region). In one aspect, the transmembrane domain is one that is associated with one of the other domains of the TFP is used. In some instances, the transmembrane domain can be selected or modified by amino acid substitution to avoid binding of such domains to the transmembrane domains of the same or different surface membrane proteins, e.g., to minimize interactions with other members of the receptor complex. In one aspect, the transmembrane domain is capable of homodimerization with another TFP on the TFP-T-cell surface. In a different aspect, the amino acid sequence of the transmembrane domain may be modified or substituted so as to minimize interactions with the binding domains of the native binding partner present in the same TFP. 
     The transmembrane domain may be derived either from a natural or from a recombinant source. Where the source is natural, the domain may be derived from any membrane-bound or transmembrane protein. In one aspect, the transmembrane domain is capable of signaling to the intracellular domain(s) whenever the TFP has bound to a target. A transmembrane domain of particular use in this invention may include at least the transmembrane region(s) of e.g., the alpha, beta or zeta chain of the T-cell receptor, CD28, CD3 epsilon, CD45, CD4, CD5, CD8, CD9, CD16, CD22, CD33, CD37, CD64, CD80, CD86, CD134, CD137, CD154. 
     In some instances, the transmembrane domain can be attached to the extracellular region of the TFP, e.g., the antigen binding domain of the TFP, via a hinge, e.g., a hinge from a human protein. For example, in one embodiment, the hinge can be a human immunoglobulin (Ig) hinge, e.g., an IgG4 hinge, or a CD8a hinge. 
     Linkers 
     Optionally, a short oligo- or polypeptide linker, between 2 and 10 amino acids in length may form the linkage between the transmembrane domain and the cytoplasmic region of the TFP. A glycine-serine doublet provides a particularly suitable linker. For example, in one aspect, the linker comprises the amino acid sequence of GGGGSGGGGSGGGGSLE (SEQ ID NO:1). In some embodiments, the linker is encoded by a nucleotide sequence of AAAIEVMYPPPYLGGGGSGGGGSGGGGSLE (SEQ ID NO:3). 
     Cytoplasmic Domain 
     The cytoplasmic domain of the TFP can include an intracellular signaling domain, if the TFP contains CD3 gamma, delta or epsilon polypeptides; TCR alpha and TCR beta subunits are generally lacking in a signaling domain. An intracellular signaling domain is generally responsible for activation of at least one of the normal effector functions of the immune cell in which the TFP has been introduced. The term “effector function” refers to a specialized function of a cell. Effector function of a T-cell, for example, may be cytolytic activity or helper activity including the secretion of cytokines. Thus, the term “intracellular signaling domain” refers to the portion of a protein which transduces the effector function signal and directs the cell to perform a specialized function. While usually the entire intracellular signaling domain can be employed, in many cases it is not necessary to use the entire chain. To the extent that a truncated portion of the intracellular signaling domain is used, such truncated portion may be used in place of the intact chain as long as it transduces the effector function signal. The term intracellular signaling domain is thus meant to include any truncated portion of the intracellular signaling domain sufficient to transduce the effector function signal. 
     Examples of intracellular signaling domains for use in the TFP of the invention include the cytoplasmic sequences of the T-cell receptor (TCR) and co-receptors that act in concert to initiate signal transduction following antigen receptor engagement, as well as any derivative or variant of these sequences and any recombinant sequence that has the same functional capability. 
     It is known that signals generated through the TCR alone are insufficient for full activation of naive T cells and that a secondary and/or co-stimulatory signal is required. Thus, naïve T-cell activation can be said to be mediated by two distinct classes of cytoplasmic signaling sequences: those that initiate antigen-dependent primary activation through the TCR (primary intracellular signaling domains) and those that act in an antigen-independent manner to provide a secondary or co-stimulatory signal (secondary cytoplasmic domain, e.g., a co-stimulatory domain). 
     A primary signaling domain regulates primary activation of the TCR complex either in a stimulatory way, or in an inhibitory way. Primary intracellular signaling domains that act in a stimulatory manner may contain signaling motifs which are known as immunoreceptor tyrosine-based activation motifs (ITAMs). 
     Examples of ITAMs containing primary intracellular signaling domains that are of particular use in the invention include those of CD3 zeta, FcR gamma, FcR beta, CD3 gamma, CD3 delta, CD3 epsilon, CD5, CD22, CD79a, CD79b, and CD66d. In one embodiment, a TFP of the invention comprises an intracellular signaling domain, e.g., a primary signaling domain of CD3-epsilon. In one embodiment, a primary signaling domain comprises a modified ITAM domain, e.g., a mutated ITAM domain which has altered (e.g., increased or decreased) activity as compared to the native ITAM domain. In one embodiment, a primary signaling domain comprises a modified ITAM-containing primary intracellular signaling domain, e.g., an optimized and/or truncated ITAM-containing primary intracellular signaling domain. In an embodiment, a primary signaling domain comprises one, two, three, four or more ITAM motifs. 
     The intracellular signaling domain of the TFP can comprise the CD3 zeta signaling domain by itself or it can be combined with any other desired intracellular signaling domain(s) useful in the context of a TFP of the invention. For example, the intracellular signaling domain of the TFP can comprise a CD3 epsilon chain portion and a co-stimulatory signaling domain. The co-stimulatory signaling domain refers to a portion of the TFP comprising the intracellular domain of a co-stimulatory molecule. A co-stimulatory molecule is a cell surface molecule other than an antigen receptor or its ligands that is required for an efficient response of lymphocytes to an antigen. Examples of such molecules include CD27, CD28, 4-1BB (CD137), OX40, DAP10, DAP12, CD30, CD40, PD-1, ICOS, lymphocyte function-associated antigen-1 (LFA-1), CD2, CD7, LIGHT, NKG2C, B7-H3, and a ligand that specifically binds with CD83, and the like. For example, CD27 co-stimulation has been demonstrated to enhance expansion, effector function, and survival of human TFP-T cells in vitro and augments human T-cell persistence and antitumor activity in vivo (Song et al. Blood. 2012; 119(3):696-706). 
     The intracellular signaling sequences within the cytoplasmic portion of the TFP of the invention may be linked to each other in a random or specified order. Optionally, a short oligo- or polypeptide linker, for example, between 2 and 10 amino acids (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids) in length may form the linkage between intracellular signaling sequences. 
     In one embodiment, a glycine-serine doublet can be used as a suitable linker. In one embodiment, a single amino acid, e.g., an alanine, a glycine, can be used as a suitable linker. 
     In one aspect, the TFP-expressing cell described herein can further comprise a second TFP, e.g., a second TFP that includes an antigen binding domain to a cell surface target (e.g., CD123). TFPs comprising antigen-binding domains that may be combined with the PD-1 TFP disclosed herein are described, e.g., in co-pending international (PCT) Application No. PCT. US2016/033146, herein incorporated by reference. 
     In another aspect, the TFP-expressing cell or second TFP-expressing cell described herein can further express another agent, e.g., an agent which enhances the activity of a TFP-expressing cell. For example, in one embodiment, the agent can be an agent which inhibits an inhibitory molecule. Inhibitory molecules, e.g., PD-1, can, in some embodiments, decrease the ability of a TFP-expressing cell to mount an immune effector response. Examples of inhibitory molecules include PD-1, PD-L1, CTLA-4 (also CTLA4 or CD152), TIM3, LAG3, VISTA, BTLA, TIGIT, LAIR1, CD160, 2B4 and TGFR beta. In one embodiment, the agent that inhibits an inhibitory molecule comprises a first polypeptide, e.g., an inhibitory molecule, associated with a second polypeptide that provides a positive signal to the cell, e.g., an intracellular signaling domain described herein. In one embodiment, the agent comprises a first polypeptide, e.g., of an inhibitory molecule such as PD-1, PD-L1, CTLA-4, TIM3, LAG3, VISTA, BTLA, TIGIT, LAIR1, PD-10, 2B4 and TGFR beta, or a fragment of any of these (e.g., at least a portion of an extracellular domain of any of these), and a second polypeptide which is an intracellular signaling domain described herein (e.g., comprising a co-stimulatory domain (e.g., 4-1BB, CD27 or CD28, e.g., as described herein) and/or a primary signaling domain (e.g., a CD3 zeta signaling domain described herein). In one embodiment, the agent comprises a first polypeptide of PD-1 or a fragment thereof (e.g., at least a portion of an extracellular domain of PD-1), and a second polypeptide of an intracellular signaling domain described herein (e.g., a CD28 signaling domain described herein and/or a CD3 zeta signaling domain described herein). PD-1 is an inhibitory member of the CD28 family of receptors that also includes CD28, CTLA-4, ICOS, and BTLA. PD-1 is expressed on activated B cells, T cells and myeloid cells (Agata et al. 1996 Int. Immunol 8:765-75). Two ligands for PD-1, PD-L1 and PD-L2 have been shown to downregulate T-cell activation upon binding to PD-1 (Freeman et al. 2000 J Exp Med 192:1027-34; Latchman et al. 2001 Nat Immunol 2:261-8; Carter et al. 2002 Eur J Immunol 32:634-43). PD-L1 is abundant in human cancers (Dong et al. 2003 J Mol Med 81:281-7; Blank et al. 2005 Cancer Immunol. Immunother 54:307-314; Konishi et al. 2004 Clin Cancer Res 10:5094) Immune suppression can be reversed by inhibiting the local interaction of PD-1 with PD-L1. 
     In one embodiment, the agent comprises the extracellular domain (ECD) of an inhibitory molecule, e.g., Programmed Death 1 (PD-1) can be fused to a transmembrane domain and optionally an intracellular signaling domain such as 41BB and CD3 zeta (also referred to herein as a PD-1 switch). In one embodiment, the PD-1 switch, when used in combinations with an anti-TAA TFP described herein, improves the persistence of the T-cell. In one embodiment, the TFP is a TAA TFP comprising the extracellular domain of a TAA. 
     In another aspect, disclosed herein is a population of TFP-expressing T cells, e.g., TFP-T cells. In some embodiments, the population of TFP-expressing T cells comprises a mixture of cells expressing different TFPs. For example, in one embodiment, the population of TFP-T cells can include a cell expressing a PD-1 fusion protein and a TFP having an scFv specific to a tumor-cell-associated antigen. As another example, the population of TFP-expressing cells can include a first cell expressing a fusion protein that comprises a PD-1 polypeptide or fragment thereof, e.g., as described herein, and a second cell expressing a TFP that includes an antigen binding domain to a tumor-associated antigen. 
     In another aspect, the present invention provides a population of cells wherein at least one cell in the population expresses a fusion protein having a PD-1 ligand binding domain described herein, at least one cell expressing an anti-TAA TFP, and a third cell expressing another agent, e.g., an agent which enhances the activity of a TFP-expressing cell. For example, in one embodiment, the agent can be an agent which inhibits an inhibitory molecule. Inhibitory molecules, e.g., can, in some embodiments, decrease the ability of a TFP-expressing cell to mount an immune effector response. Examples of inhibitory molecules include PD-1, PD-L1, CTLA-4, TIM3, LAG3, VISTA, BTLA, TIGIT, LAIR1, CD160, 2B4 and TGFR beta. In one embodiment, the agent that inhibits an inhibitory molecule comprises a first polypeptide, e.g., an inhibitory molecule, associated with a second polypeptide that provides a positive signal to the cell, e.g., an intracellular signaling domain described herein. 
     In another embodiment, one or more domains of the TFP construct (e.g., extracellular, transmembrane, and intracellular signaling domain) or the T cell genome (e.g., one or more endogenous genes such as the gene encoding PD1) are engineered, modified, or deleted using a gene editing technique such as clustered regularly interspaced short palindromic repeats (CRISPR®, see, e.g., U.S. Pat. No. 8,697,359), transcription activator-like effector nucleases (TALEN, see, e.g., U.S. Pat. No. 9,393,257), meganucleases (naturally occurring endodeoxyribonucleases having large recognition sites comprising double-stranded DNA sequences of 12 to 40 base pairs), or zinc finger nuclease (ZFN, see, e.g., Urnov et al., Nat. Rev. Genetics (2010) v11, 636-646) methods. In this way, a chimeric construct may be engineered to combine desirable characteristics of each subunit, such as conformation or signaling capabilities. See also Sander &amp; Joung, Nat. Biotech. (2014) v32, 347-55; and June et al., 2009 Nature Reviews Immunol. 9.10: 704-716, each incorporated herein by reference. In some embodiments, one or more of the extracellular domain, the transmembrane domain, or the cytoplasmic domain of a TFP subunit or PD-1 switch are engineered to have aspects of more than one natural TCR subunit domain (i.e., are chimeric). 
     Disclosed herein are methods for producing in vitro transcribed RNA encoding TFPs. The present invention also includes a TFP encoding RNA construct that can be directly transfected into a cell. A method for generating mRNA for use in transfection can involve in vitro transcription (IVT) of a template with specially designed primers, followed by polyA addition, to produce a construct containing 3′ and 5′ untranslated sequence (“UTR”), a 5′ cap and/or Internal Ribosome Entry Site (IRES), the nucleic acid to be expressed, and a polyA tail, typically 50-2000 bases in length (SEQ ID NO: 27). RNA so produced can efficiently transfect different kinds of cells. In one aspect, the template includes sequences for the TFP. 
     In one aspect, the PD-1 fusion protein and/or anti-TAA TFP is encoded by a messenger RNA (mRNA). In one aspect, the mRNA encoding the PD-1 fusion protein and/or anti-TAA TFP is introduced into a T-cell for production of a TFP-T-cell. In one embodiment, the in vitro transcribed RNA TFP can be introduced to a cell as a form of transient transfection. The RNA is produced by in vitro transcription using a polymerase chain reaction (PCR)-generated template. DNA of interest from any source can be directly converted by PCR into a template for in vitro mRNA synthesis using appropriate primers and RNA polymerase. The source of the DNA can be, for example, genomic DNA, plasmid DNA, phage DNA, cDNA, synthetic DNA sequence or any other appropriate source of DNA. The desired template for in vitro transcription is a TFP of the present invention. In one embodiment, the DNA to be used for PCR contains an open reading frame. The DNA can be from a naturally occurring DNA sequence from the genome of an organism. In one embodiment, the nucleic acid can include some or all of the 5′ and/or 3′ untranslated regions (UTRs). The nucleic acid can include exons and introns. In one embodiment, the DNA to be used for PCR is a human nucleic acid sequence. In another embodiment, the DNA to be used for PCR is a human nucleic acid sequence including the 5′ and 3′ UTRs. The DNA can alternatively be an artificial DNA sequence that is not normally expressed in a naturally occurring organism. An exemplary artificial DNA sequence is one that contains portions of genes that are ligated together to form an open reading frame that encodes a fusion protein. The portions of DNA that are ligated together can be from a single organism or from more than one organism. 
     PCR is used to generate a template for in vitro transcription of mRNA which is used for transfection. Methods for performing PCR are well known in the art. Primers for use in PCR are designed to have regions that are substantially complementary to regions of the DNA to be used as a template for the PCR. “Substantially complementary,” as used herein, refers to sequences of nucleotides where a majority or all of the bases in the primer sequence are complementary, or one or more bases are non-complementary, or mismatched. Substantially complementary sequences are able to anneal or hybridize with the intended DNA target under annealing conditions used for PCR. The primers can be designed to be substantially complementary to any portion of the DNA template. For example, the primers can be designed to amplify the portion of a nucleic acid that is normally transcribed in cells (the open reading frame), including 5′ and 3′ UTRs. The primers can also be designed to amplify a portion of a nucleic acid that encodes a particular domain of interest. In one embodiment, the primers are designed to amplify the coding region of a human cDNA, including all or portions of the 5′ and 3′ UTRs. Primers useful for PCR can be generated by synthetic methods that are well known in the art. “Forward primers” are primers that contain a region of nucleotides that are substantially complementary to nucleotides on the DNA template that are upstream of the DNA sequence that is to be amplified. “Upstream” is used herein to refer to a location 5, to the DNA sequence to be amplified relative to the coding strand. “Reverse primers” are primers that contain a region of nucleotides that are substantially complementary to a double-stranded DNA template that are downstream of the DNA sequence that is to be amplified. “Downstream” is used herein to refer to a location 3′ to the DNA sequence to be amplified relative to the coding strand. 
     Any DNA polymerase useful for PCR can be used in the methods disclosed herein. The reagents and polymerase are commercially available from a number of sources. 
     Chemical structures with the ability to promote stability and/or translation efficiency may also be used. The RNA preferably has 5′ and 3′ UTRs. In one embodiment, the 5′ UTR is between one and 3,000 nucleotides in length. The length of 5′ and 3′ UTR sequences to be added to the coding region can be altered by different methods, including, but not limited to, designing primers for PCR that anneal to different regions of the UTRs. Using this approach, one of ordinary skill in the art can modify the 5′ and 3′ UTR lengths required to achieve optimal translation efficiency following transfection of the transcribed RNA. 
     The 5′ and 3′ UTRs can be the naturally occurring, endogenous 5′ and 3′ UTRs for the nucleic acid of interest. Alternatively, UTR sequences that are not endogenous to the nucleic acid of interest can be added by incorporating the UTR sequences into the forward and reverse primers or by any other modifications of the template. The use of UTR sequences that are not endogenous to the nucleic acid of interest can be useful for modifying the stability and/or translation efficiency of the RNA. For example, it is known that AU-rich elements in 3′UTR sequences can decrease the stability of mRNA. Therefore, 3′ UTRs can be selected or designed to increase the stability of the transcribed RNA based on properties of UTRs that are well known in the art. 
     In one embodiment, the 5′ UTR can contain the Kozak sequence of the endogenous nucleic acid. Alternatively, when a 5′ UTR that is not endogenous to the nucleic acid of interest is being added by PCR as described above, a consensus Kozak sequence can be redesigned by adding the 5′ UTR sequence. Kozak sequences can increase the efficiency of translation of some RNA transcripts, but does not appear to be required for all RNAs to enable efficient translation. The requirement for Kozak sequences for many mRNAs is known in the art. In other embodiments, the 5′ UTR can be 5′UTR of an RNA virus whose RNA genome is stable in cells. In other embodiments, various nucleotide analogues can be used in the 3′ or 5′ UTR to impede exonuclease degradation of the mRNA. 
     To enable synthesis of RNA from a DNA template without the need for gene cloning, a promoter of transcription should be attached to the DNA template upstream of the sequence to be transcribed. When a sequence that functions as a promoter for an RNA polymerase is added to the 5′ end of the forward primer, the RNA polymerase promoter becomes incorporated into the PCR product upstream of the open reading frame that is to be transcribed. In one preferred embodiment, the promoter is a T7 polymerase promoter, as described elsewhere herein. Other useful promoters include, but are not limited to, T3 and SP6 RNA polymerase promoters. Consensus nucleotide sequences for T7, T3 and SP6 promoters are known in the art. 
     In one embodiment, the mRNA has both a cap on the 5′ end and a 3′ poly(A) tail which determine ribosome binding, initiation of translation and stability mRNA in the cell. On a circular DNA template, for instance, plasmid DNA, RNA polymerase produces a long concatameric product which is not suitable for expression in eukaryotic cells. The transcription of plasmid DNA linearized at the end of the 3′ UTR results in normal sized mRNA which is not effective in eukaryotic transfection even if it is polyadenylated after transcription. 
     On a linear DNA template, phage T7 RNA polymerase can extend the 3′ end of the transcript beyond the last base of the template (Schenborn and Mierendorf, Nuc Acids Res., 13:6223-36 (1985); Nacheva and Berzal-Herranz, Eur. J. Biochem., 270:1485-65 (2003). 
     The conventional method of integration of polyA/T stretches into a DNA template is molecular cloning. However, polyA/T sequence integrated into plasmid DNA can cause plasmid instability, which is why plasmid DNA templates obtained from bacterial cells are often highly contaminated with deletions and other aberrations. This makes cloning procedures not only laborious and time consuming but often not reliable. That is why a method which allows construction of DNA templates with polyA/T 3′ stretch without cloning highly desirable. 
     The polyA/T segment of the transcriptional DNA template can be produced during PCR by using a reverse primer containing a polyT tail, such as 100 T tail (SEQ ID NO: 28) (size can be 50-5000 Ts (SEQ ID NO: 29)), or after PCR by any other method, including, but not limited to, DNA ligation or in vitro recombination. Poly(A) tails also provide stability to RNAs and reduce their degradation. Generally, the length of a poly(A) tail positively correlates with the stability of the transcribed RNA. In one embodiment, the poly(A) tail is between 100 and 5000 adenosines (SEQ ID NO: 30). 
     Poly(A) tails of RNAs can be further extended following in vitro transcription with the use of a poly(A) polymerase, such as  E. coli  polyA polymerase (E-PAP). In one embodiment, increasing the length of a poly(A) tail from 100 nucleotides to between 300 and 400 nucleotides (SEQ ID NO: 31) results in about a two-fold increase in the translation efficiency of the RNA. Additionally, the attachment of different chemical groups to the 3′ end can increase mRNA stability. Such attachment can contain modified/artificial nucleotides, aptamers and other compounds. For example, ATP analogs can be incorporated into the poly(A) tail using poly(A) polymerase. ATP analogs can further increase the stability of the RNA. 
     5′ caps on also provide stability to RNA molecules. In a preferred embodiment, RNAs produced by the methods disclosed herein include a 5′ cap. The 5′ cap is provided using techniques known in the art and described herein (Cougot, et al., Trends in Biochem. Sci., 29:436-444 (2001); Stepinski, et al., RNA, 7:1468-95 (2001); Elango, et al., Biochim Biophys. Res. Commun., 330:958-966 (2005)). 
     The RNAs produced by the methods disclosed herein can also contain an internal ribosome entry site (IRES) sequence. The IRES sequence may be any viral, chromosomal or artificially designed sequence which initiates cap-independent ribosome binding to mRNA and facilitates the initiation of translation. Any solutes suitable for cell electroporation, which can contain factors facilitating cellular permeability and viability such as sugars, peptides, lipids, proteins, antioxidants, and surfactants can be included. 
     RNA can be introduced into target cells using any of a number of different methods, for instance, commercially available methods which include, but are not limited to, electroporation (Amaxa Nucleofector-II (Amaxa Biosystems, Cologne, Germany)), (ECM 830 (BTX) (Harvard Instruments, Boston, Mass.) or the Gene Pulser II (BioRad, Denver, Colo.), Multiporator (Eppendort, Hamburg Germany), cationic liposome mediated transfection using lipofection, polymer encapsulation, peptide mediated transfection, or biolistic particle delivery systems such as “gene guns” (see, for example, Nishikawa, et al. Hum Gene Ther., 12(8):861-70 (2001). 
     Nucleic Acid Constructs Encoding a TFP or a PD-1 Fusion Protein 
     The present invention also provides nucleic acid molecules encoding one or more TFP constructs and/or PD-1 fusion proteins described herein. In one aspect, the nucleic acid molecule is provided as a messenger RNA transcript. In one aspect, the nucleic acid molecule is provided as a DNA construct. 
     The nucleic acid sequences coding for the desired molecules can be obtained using recombinant methods known in the art, such as, for example by screening libraries from cells expressing the gene, by deriving the gene from a vector known to include the same, or by isolating directly from cells and tissues containing the same, using standard techniques. Alternatively, the gene of interest can be produced synthetically, rather than cloned. 
     The present invention also provides vectors in which a DNA of the present invention is inserted. Vectors derived from retroviruses such as the lentivirus are suitable tools to achieve long-term gene transfer since they allow long-term, stable integration of a transgene and its propagation in daughter cells. Lentiviral vectors have the added advantage over vectors derived from onco-retroviruses such as murine leukemia viruses in that they can transduce non-proliferating cells, such as hepatocytes. They also have the added advantage of low immunogenicity. 
     In another embodiment, the vector comprising the nucleic acid encoding the desired TFP or switch of the invention is an adenoviral vector (A5/35). In another embodiment, the expression of nucleic acids encoding TFPs can be accomplished using of transposons such as sleeping beauty, crisper, CAS9, and zinc finger nucleases (See, June et al. 2009 Nature Reviews Immunol. 9.10: 704-716, incorporated herein by reference). 
     The expression constructs of the present invention may also be used for nucleic acid immunization and gene therapy, using standard gene delivery protocols. Methods for gene delivery are known in the art (see, e.g., U.S. Pat. Nos. 5,399,346, 5,580,859, 5,589,466, incorporated by reference herein in their entireties). In another embodiment, the invention provides a gene therapy vector. 
     The nucleic acid can be cloned into a number of types of vectors. For example, the nucleic acid can be cloned into a vector including, but not limited to a plasmid, a phagemid, a phage derivative, an animal virus, and a cosmid. Vectors of particular interest include expression vectors, replication vectors, probe generation vectors, and sequencing vectors. 
     Further, the expression vector may be provided to a cell in the form of a viral vector. Viral vector technology is well known in the art and is described, e.g., in Sambrook et al., 2012, Molecular Cloning: A Laboratory Manual, volumes 1-4, Cold Spring Harbor Press, NY), and in other virology and molecular biology manuals. Viruses, which are useful as vectors include, but are not limited to, retroviruses, adenoviruses, adeno-associated viruses, herpes viruses, and lentiviruses. In general, a suitable vector contains an origin of replication functional in at least one organism, a promoter sequence, convenient restriction endonuclease sites, and one or more selectable markers (e.g., WO 01/96584; WO 01/29058; and U.S. Pat. No. 6,326,193). 
     A number of virally based systems have been developed for gene transfer into mammalian cells. For example, retroviruses provide a convenient platform for gene delivery systems. A selected gene can be inserted into a vector and packaged in retroviral particles using techniques known in the art. The recombinant virus can then be isolated and delivered to cells of the subject either in vivo or ex vivo. A number of retroviral systems are known in the art. In some embodiments, adenovirus vectors are used. A number of adenovirus vectors are known in the art. In one embodiment, lentivirus vectors are used. 
     Additional promoter elements, e.g., enhancers, regulate the frequency of transcriptional initiation. Typically, these are located in the region 30-110 bp upstream of the start site, although a number of promoters have been shown to contain functional elements downstream of the start site as well. The spacing between promoter elements frequently is flexible, so that promoter function is preserved when elements are inverted or moved relative to one another. In the thymidine kinase (tk) promoter, the spacing between promoter elements can be increased to 50 bp apart before activity begins to decline. Depending on the promoter, it appears that individual elements can function either cooperatively or independently to activate transcription. 
     An example of a promoter that is capable of expressing a TFP transgene in a mammalian T-cell is the EF1a promoter. The native EF1a promoter drives expression of the alpha subunit of the elongation factor-1 complex, which is responsible for the enzymatic delivery of aminoacyl tRNAs to the ribosome. The EF1a promoter has been extensively used in mammalian expression plasmids and has been shown to be effective in driving TFP expression from transgenes cloned into a lentiviral vector (see, e.g., Milone et al., Mol. Ther. 17(8): 1453-1464 (2009)). Another example of a promoter is the immediate early cytomegalovirus (CMV) promoter sequence. This promoter sequence is a strong constitutive promoter sequence capable of driving high levels of expression of any polynucleotide sequence operatively linked thereto. However, other constitutive promoter sequences may also be used, including, but not limited to the simian virus 40 (SV40) early promoter, mouse mammary tumor virus (MMTV), human immunodeficiency virus (HIV) long terminal repeat (LTR) promoter, MoMuLV promoter, an avian leukemia virus promoter, an Epstein-Barr virus immediate early promoter, a Rous sarcoma virus promoter, as well as human gene promoters such as, but not limited to, the actin promoter, the myosin promoter, the elongation factor-1a promoter, the hemoglobin promoter, and the creatine kinase promoter. Further, the invention should not be limited to the use of constitutive promoters. Inducible promoters are also contemplated as part of the invention. The use of an inducible promoter provides a molecular switch capable of turning on expression of the polynucleotide sequence which it is operatively linked when such expression is desired, or turning off the expression when expression is not desired. Examples of inducible promoters include, but are not limited to a metallothionine promoter, a glucocorticoid promoter, a progesterone promoter, and a tetracycline-regulated promoter. 
     In order to assess the expression of a TFP polypeptide or portions thereof, the expression vector to be introduced into a cell can also contain either a selectable marker gene or a reporter gene or both to facilitate identification and selection of expressing cells from the population of cells sought to be transfected or infected through viral vectors. In other aspects, the selectable marker may be carried on a separate piece of DNA and used in a co-transfection procedure. Both selectable markers and reporter genes may be flanked with appropriate regulatory sequences to enable expression in the host cells. Useful selectable markers include, for example, antibiotic-resistance genes, such as neo and the like. 
     Reporter genes are used for identifying potentially transfected cells and for evaluating the functionality of regulatory sequences. In general, a reporter gene is a gene that is not present in or expressed by the recipient organism or tissue and that encodes a polypeptide whose expression is manifested by some easily detectable property, e.g., enzymatic activity. Expression of the reporter gene is assayed at a suitable time after the DNA has been introduced into the recipient cells. Suitable reporter genes may include genes encoding luciferase, beta-galactosidase, chloramphenicol acetyl transferase, secreted alkaline phosphatase, or the green fluorescent protein gene (e.g., Ui-Tei et al., 2000 FEBS Letters 479: 79-82). Suitable expression systems are well known and may be prepared using known techniques or obtained commercially. In general, the construct with the minimal 5′ flanking region showing the highest level of expression of reporter gene is identified as the promoter. Such promoter regions may be linked to a reporter gene and used to evaluate agents for the ability to modulate promoter-driven transcription. 
     Methods of introducing and expressing genes into a cell are known in the art. In the context of an expression vector, the vector can be readily introduced into a host cell, e.g., mammalian, bacterial, yeast, or insect cell by any method in the art. For example, the expression vector can be transferred into a host cell by physical, chemical, or biological means. 
     Physical methods for introducing a polynucleotide into a host cell include calcium phosphate precipitation, lipofection, particle bombardment, microinjection, electroporation, and the like. Methods for producing cells comprising vectors and/or exogenous nucleic acids are well-known in the art (see, e.g., Sambrook et al., 2012, Molecular Cloning: A Laboratory Manual, volumes 1-4, Cold Spring Harbor Press, NY). One method for the introduction of a polynucleotide into a host cell is calcium phosphate transfection 
     Biological methods for introducing a polynucleotide of interest into a host cell include the use of DNA and RNA vectors. Viral vectors, and especially retroviral vectors, have become the most widely used method for inserting genes into mammalian, e.g., human cells. Other viral vectors can be derived from lentivirus, poxviruses, herpes simplex virus I, adenoviruses and adeno-associated viruses, and the like (see, e.g., U.S. Pat. Nos. 5,350,674 and 5,585,362. 
     Chemical means for introducing a polynucleotide into a host cell include colloidal dispersion systems, such as macromolecule complexes, nanocapsules, microspheres, beads, and lipid-based systems including oil-in-water emulsions, micelles, mixed micelles, and liposomes. An exemplary colloidal system for use as a delivery vehicle in vitro and in vivo is a liposome (e.g., an artificial membrane vesicle). Other methods of state-of-the-art targeted delivery of nucleic acids are available, such as delivery of polynucleotides with targeted nanoparticles or other suitable sub-micron sized delivery system. 
     In the case where a non-viral delivery system is utilized, an exemplary delivery vehicle is a liposome. The use of lipid formulations is contemplated for the introduction of the nucleic acids into a host cell (in vitro, ex vivo or in vivo). In another aspect, the nucleic acid may be associated with a lipid. The nucleic acid associated with a lipid may be encapsulated in the aqueous interior of a liposome, interspersed within the lipid bilayer of a liposome, attached to a liposome via a linking molecule that is associated with both the liposome and the oligonucleotide, entrapped in a liposome, complexed with a liposome, dispersed in a solution containing a lipid, mixed with a lipid, combined with a lipid, contained as a suspension in a lipid, contained or complexed with a micelle, or otherwise associated with a lipid. Lipid, lipid/DNA or lipid/expression vector associated compositions are not limited to any particular structure in solution. For example, they may be present in a bilayer structure, as micelles, or with a “collapsed” structure. They may also simply be interspersed in a solution, possibly forming aggregates that are not uniform in size or shape. Lipids are fatty substances which may be naturally occurring or synthetic lipids. For example, lipids include the fatty droplets that naturally occur in the cytoplasm as well as the class of compounds which contain long-chain aliphatic hydrocarbons and their derivatives, such as fatty acids, alcohols, amines, amino alcohols, and aldehydes. 
     Lipids suitable for use can be obtained from commercial sources. For example, dimyristyl phosphatidylcholine (“DMPC”) can be obtained from Sigma, St. Louis, Mo.; dicetyl phosphate (“DCP”) can be obtained from K &amp; K Laboratories (Plainview, N.Y.); cholesterol (“Choi”) can be obtained from Calbiochem-Behring; dimyristyl phosphatidylglycerol (“DMPG”) and other lipids may be obtained from Avanti Polar Lipids, Inc. (Birmingham, Ala.). Stock solutions of lipids in chloroform or chloroform/methanol can be stored at about −20° C. Chloroform is used as the only solvent since it is more readily evaporated than methanol. “Liposome” is a generic term encompassing a variety of single and multilamellar lipid vehicles formed by the generation of enclosed lipid bilayers or aggregates. Liposomes can be characterized as having vesicular structures with a phospholipid bilayer membrane and an inner aqueous medium. Multilamellar liposomes have multiple lipid layers separated by aqueous medium. They form spontaneously when phospholipids are suspended in an excess of aqueous solution. The lipid components undergo self-rearrangement before the formation of closed structures and entrap water and dissolved solutes between the lipid bilayers (Ghosh et al., 1991 Glycobiology 5: 505-10). However, compositions that have different structures in solution than the normal vesicular structure are also encompassed. For example, the lipids may assume a micellar structure or merely exist as nonuniform aggregates of lipid molecules. Also contemplated are lipofectamine-nucleic acid complexes. 
     Regardless of the method used to introduce exogenous nucleic acids into a host cell or otherwise expose a cell to the inhibitor of the present invention, in order to confirm the presence of the recombinant DNA sequence in the host cell, a variety of assays may be performed. Such assays include, for example, “molecular biological” assays well known to those of skill in the art, such as Southern and Northern blotting, RT-PCR and PCR; “biochemical” assays, such as detecting the presence or absence of a particular peptide, e.g., by immunological means (ELISAs and western blots) or by assays described herein to identify agents falling within the scope of the invention. 
     The present invention further provides a vector comprising a TFP encoding nucleic acid molecule. In one aspect, a TFP vector can be directly transduced into a cell, e.g., a T-cell. In one aspect, the vector is a cloning or expression vector, e.g., a vector including, but not limited to, one or more plasmids (e.g., expression plasmids, cloning vectors, minicircles, minivectors, double minute chromosomes), retroviral and lentiviral vector constructs. In one aspect, the vector is capable of expressing the TFP construct in mammalian T cells. In one aspect, the mammalian T-cell is a human T-cell. 
     Sources of T Cells 
     Prior to expansion and genetic modification, a source of T cells is obtained from a subject. The term “subject” is intended to include living organisms in which an immune response can be elicited (e.g., mammals). Examples of subjects include humans, dogs, cats, mice, rats, and transgenic species thereof. T cells can be obtained from a number of sources, including peripheral blood mononuclear cells, bone marrow, lymph node tissue, cord blood, thymus tissue, tissue from a site of infection, ascites, pleural effusion, spleen tissue, and tumors. In certain aspects of the present invention, any number of T-cell lines available in the art, may be used. In certain aspects of the present invention, T cells can be obtained from a unit of blood collected from a subject using any number of techniques known to the skilled artisan, such as Ficoll® separation. In one preferred aspect, cells from the circulating blood of an individual are obtained by apheresis. The apheresis product typically contains lymphocytes, including T cells, monocytes, granulocytes, B cells, other nucleated white blood cells, red blood cells, and platelets. In one aspect, the cells collected by apheresis may be washed to remove the plasma fraction and to place the cells in an appropriate buffer or media for subsequent processing steps. In one aspect of the invention, the cells are washed with phosphate buffered saline (PBS). In an alternative aspect, the wash solution lacks calcium and may lack magnesium or may lack many if not all divalent cations. Initial activation steps in the absence of calcium can lead to magnified activation. As those of ordinary skill in the art would readily appreciate a washing step may be accomplished by methods known to those in the art, such as by using a semi-automated “flow-through” centrifuge (for example, the Cobe 2991 cell processor, the Baxter CytoMate™, or the Haemonetics® Cell Saver® 5) according to the manufacturer&#39;s instructions. After washing, the cells may be resuspended in a variety of biocompatible buffers, such as, for example, Ca-free, Mg-free PBS, Plasma-Lyte® A, or other saline solution with or without buffer. Alternatively, the undesirable components of the apheresis sample may be removed and the cells directly resuspended in culture media. 
     In one aspect, T cells are isolated from peripheral blood lymphocytes by lysing the red blood cells and depleting the monocytes, for example, by centrifugation through a PERCOLL™ gradient or by counterflow centrifugal elutriation. A specific subpopulation of T cells, such as CD3+, CD28+, CD4+, CD8+, CD45RA+, and CD45RO+ T cells, can be further isolated by positive or negative selection techniques. For example, in one aspect, T cells are isolated by incubation with anti-CD3/anti-CD28 (e.g., 3×28)-conjugated beads, such as DYNABEADS® M-450 CD3/CD28 T, for a time period sufficient for positive selection of the desired T cells. In one aspect, the time period is about 30 minutes. In a further aspect, the time period ranges from 30 minutes to 36 hours or longer and all integer values there between. In a further aspect, the time period is at least 1, 2, 3, 4, 5, or 6 hours. In yet another preferred aspect, the time period is 10 to 24 hours. In one aspect, the incubation time period is 24 hours. Longer incubation times may be used to isolate T cells in any situation where there are few T cells as compared to other cell types, such in isolating tumor infiltrating lymphocytes (TIL) from tumor tissue or from immunocompromised individuals. Further, use of longer incubation times can increase the efficiency of capture of CD8+ T cells. Thus, by simply shortening or lengthening the time T cells are allowed to bind to the CD3/CD28 beads and/or by increasing or decreasing the ratio of beads to T cells (as described further herein), subpopulations of T cells can be preferentially selected for or against at culture initiation or at other time points during the process. Additionally, by increasing or decreasing the ratio of anti-CD3 and/or anti-CD28 antibodies on the beads or other surface, subpopulations of T cells can be preferentially selected for or against at culture initiation or at other desired time points. The skilled artisan would recognize that multiple rounds of selection can also be used in the context of this invention. In certain aspects, it may be desirable to perform the selection procedure and use the “unselected” cells in the activation and expansion process. “Unselected” cells can also be subjected to further rounds of selection. 
     Enrichment of a T-cell population by negative selection can be accomplished with a combination of antibodies directed to surface markers unique to the negatively selected cells. One method is cell sorting and/or selection via negative magnetic immunoadherence or flow cytometry that uses a cocktail of monoclonal antibodies directed to cell surface markers present on the cells negatively selected. For example, to enrich for CD4+ cells by negative selection, a monoclonal antibody cocktail typically includes antibodies to CD14, CD20, CD11b, CD16, HLA-DR, and CD8. In certain aspects, it may be desirable to enrich for or positively select for regulatory T cells which typically express CD4+, CD25+, CD62Lhi, GITR+, and FoxP3+. Alternatively, in certain aspects, T regulatory cells are depleted by anti-C25 conjugated beads or other similar method of selection. 
     In one embodiment, a T-cell population can be selected that expresses one or more of IFN-γ, C TNF-alpha, IL-17A, IL-2, IL-3, IL-4, GM-CSF, IL-10, IL-13, IL-12, granzyme B, and perforin, or other appropriate molecules, e.g., other cytokines. Methods for screening for cell expression can be determined, e.g., by the methods described in PCT Publication No.: WO 2013/126712. 
     For isolation of a desired population of cells by positive or negative selection, the concentration of cells and surface (e.g., particles such as beads) can be varied. In certain aspects, it may be desirable to significantly decrease the volume in which beads and cells are mixed together (e.g., increase the concentration of cells), to ensure maximum contact of cells and beads. For example, in one aspect, a concentration of 2 billion cells/mL is used. In one aspect, a concentration of 1 billion cells/mL is used. In a further aspect, greater than 100 million cells/mL is used. In a further aspect, a concentration of cells of 10, 15, 20, 25, 30, 35, 40, 45, or 50 million cells/mL is used. In yet one aspect, a concentration of cells from 75, 80, 85, 90, 95, or 100 million cells/mL is used. In further aspects, concentrations of 125 or 150 million cells/mL can be used. Using high concentrations can result in increased cell yield, cell activation, and cell expansion. Further, use of high cell concentrations allows more efficient capture of cells that may weakly express target antigens of interest, such as CD28-negative T cells, or from samples where there are many tumor cells present (e.g., leukemic blood, tumor tissue, etc.). Such populations of cells may have therapeutic value and would be desirable to obtain. For example, using high concentration of cells allows more efficient selection of CD8+ T cells that normally have weaker CD28 expression. 
     In a related aspect, it may be desirable to use lower concentrations of cells. By significantly diluting the mixture of T cells and surface (e.g., particles such as beads), interactions between the particles and cells is minimized. This selects for cells that express high amounts of desired antigens to be bound to the particles. For example, CD4+ T cells express higher levels of CD28 and are more efficiently captured than CD8+ T cells in dilute concentrations. In one aspect, the concentration of cells used is 5×10 6 /mL. In other aspects, the concentration used can be from about 1×10 5 /mL to 1×10 6 /mL, and any integer value in between. In other aspects, the cells may be incubated on a rotator for varying lengths of time at varying speeds at either 2-10° C. or at room temperature. 
     T cells for stimulation can also be frozen after a washing step. Wishing not to be bound by theory, the freeze and subsequent thaw step provides a more uniform product by removing granulocytes and to some extent monocytes in the cell population. After the washing step that removes plasma and platelets, the cells may be suspended in a freezing solution. While many freezing solutions and parameters are known in the art and will be useful in this context, one method involves using PBS containing 20% dimethyl sulfoxide (DMSO) and 8% human serum albumin, or culture media containing 10% dextran 40 and 5% dextrose, 20% human serum albumin and 7.5% DMSO, or 31.25% Plasma-Lyte®-A, 31.25% dextrose 5%, 0.45% NaCl, 10% dextran 40 and 5% Dextrose, 20% Human Serum Albumin, and 7.5% DMSO or other suitable cell freezing media containing for example, Hespan® and Plasma-Lyte-A, the cells then are frozen to −80° C. at a rate of 1 per minute and stored in the vapor phase of a liquid nitrogen storage tank. Other methods of controlled freezing may be used as well as uncontrolled freezing immediately at −20° C. or in liquid nitrogen. In certain aspects, cryopreserved cells are thawed and washed as described herein and allowed to rest for one hour at room temperature prior to activation using the methods of the present invention. 
     Also contemplated in the context of the invention is the collection of blood samples or apheresis product from a subject at a time period prior to when the expanded cells as described herein might be needed. As such, the source of the cells to be expanded can be collected at any time point necessary, and desired cells, such as T cells, isolated and frozen for later use in T-cell therapy for any number of diseases or conditions that would benefit from T-cell therapy, such as those described herein. In one aspect, a blood sample or an apheresis is taken from a generally healthy subject. In certain aspects, a blood sample or an apheresis is taken from a generally healthy subject who is at risk of developing a disease, but who has not yet developed a disease, and the cells of interest are isolated and frozen for later use. In certain aspects, the T cells may be expanded, frozen, and used at a later time. In certain aspects, samples are collected from a patient shortly after diagnosis of a particular disease as described herein but prior to any treatments. In a further aspect, the cells are isolated from a blood sample or an apheresis from a subject prior to any number of relevant treatment modalities, including but not limited to treatment with agents such as natalizumab, efalizumab, antiviral agents, chemotherapy, radiation, immunosuppressive agents, such as cyclosporine, azathioprine, methotrexate, mycophenolate, and tacrolimus, antibodies, or other immunoablative agents such as alemtuzumab, anti-CD3 antibodies, cyclophosphamide, fludarabine, cyclosporin, rapamycin, mycophenolic acid, steroids, romidepsin, and irradiation. 
     In a further aspect of the present invention, T cells are obtained from a patient directly following treatment that leaves the subject with functional T cells. In this regard, it has been observed that following certain cancer treatments, in particular treatments with drugs that damage the immune system, shortly after treatment during the period when patients would normally be recovering from the treatment, the quality of T cells obtained may be optimal or improved for their ability to expand ex vivo. Likewise, following ex vivo manipulation using the methods described herein, these cells may be in a preferred state for enhanced engraftment and in vivo expansion. Thus, it is contemplated within the context of the present invention to collect blood cells, including T cells, dendritic cells, or other cells of the hematopoietic lineage, during this recovery phase. Further, in certain aspects, mobilization (for example, mobilization with GM-CSF) and conditioning regimens can be used to create a condition in a subject wherein repopulation, recirculation, regeneration, and/or expansion of particular cell types is favored, especially during a defined window of time following therapy. Illustrative cell types include T cells, B cells, dendritic cells, and other cells of the immune system. 
     Activation and Expansion of T Cells 
     T cells may be activated and expanded generally using methods as described, for example, in U.S. Pat. Nos. 6,352,694; 6,534,055; 6,905,680; 6,692,964; 5,858,358; 6,887,466; 6,905,681; 7,144,575; 7,067,318; 7,172,869; 7,232,566; 7,175,843; 5,883,223; 6,905,874; 6,797,514; 6,867,041; and 7,572,631. 
     Generally, the T cells of the invention may be expanded by contact with a surface having attached thereto an agent that stimulates a CD3/TCR complex associated signal and a ligand that stimulates a co-stimulatory molecule on the surface of the T cells. In particular, T-cell populations may be stimulated as described herein, such as by contact with an anti-CD3 antibody, or antigen-binding fragment thereof, or an anti-CD2 antibody immobilized on a surface, or by contact with a protein kinase C activator (e.g., bryostatin) in conjunction with a calcium ionophore. For co-stimulation of an accessory molecule on the surface of the T cells, a ligand that binds the accessory molecule is used. For example, a population of T cells can be contacted with an anti-CD3 antibody and an anti-CD28 antibody, under conditions appropriate for stimulating proliferation of the T cells. To stimulate proliferation of either CD4+ T cells or CD8+ T cells, an anti-CD3 antibody and an anti-CD28 antibody. Examples of an anti-CD28 antibody include 9.3, B-T3, XR-CD28 (Diaclone, Besancon, France) can be used as can other methods commonly known in the art (Berg et al., Transplant Proc. 30(8):3975-3977, 1998; Haanen et al., J. Exp. Med. 190(9):13191328, 1999; Garland et al., J. Immunol. Meth. 227(1-2):53-63, 1999). 
     T cells that have been exposed to varied stimulation times may exhibit different characteristics. For example, typical blood or apheresed peripheral blood mononuclear cell products have a helper T-cell population (TH, CD4+) that is greater than the cytotoxic or suppressor T-cell population (TC, CD8+). Ex vivo expansion of T cells by stimulating CD3 and CD28 receptors produces a population of T cells that prior to about days 8-9 consists predominately of TH cells, while after about days 8-9, the population of T cells comprises an increasingly greater population of TC cells. Accordingly, depending on the purpose of treatment, infusing a subject with a T-cell population comprising predominately of TH cells may be advantageous. Similarly, if an antigen-specific subset of TC cells has been isolated it may be beneficial to expand this subset to a greater degree. 
     Further, in addition to CD4 and CD8 markers, other phenotypic markers vary significantly, but in large part, reproducibly during the course of the cell expansion process. Thus, such reproducibility enables the ability to tailor an activated T-cell product for specific purposes. 
     Once an anti-TAA TFP and/or PD-1 fusion protein is constructed, various assays can be used to evaluate the activity of the molecule, such as but not limited to, the ability to expand T cells following antigen stimulation, sustain T-cell expansion in the absence of re-stimulation, and anti-cancer activities in appropriate in vitro and animal models. Assays to evaluate the effects of an anti-TAA TFP and/or PD-1 fusion protein are described in further detail below 
     Western blot analysis of TFP expression in primary T cells can be used to detect the presence of monomers and dimers (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Very briefly, T cells (1:1 mixture of CD4 +  and CD8 +  T cells) expressing the TFPs are expanded in vitro for more than 10 days followed by lysis and SDS-PAGE under reducing conditions. TFPs are detected by western blotting using an antibody to a TCR chain. The same T-cell subsets are used for SDS-PAGE analysis under non-reducing conditions to permit evaluation of covalent dimer formation. 
     In vitro expansion of TFP +  T cells following antigen stimulation can be measured by flow cytometry. For example, a mixture of CD4 +  and CD8 +  T cells are stimulated with alphaCD3/alphaCD28 and APCs followed by transduction with lentiviral vectors expressing GFP under the control of the promoters to be analyzed. Exemplary promoters include the CMV IE gene, EF-1alpha, ubiquitin C, or phosphoglycerokinase (PGK) promoters. GFP fluorescence is evaluated on day 6 of culture in the CD4+ and/or CD8+ T-cell subsets by flow cytometry (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Alternatively, a mixture of CD4+ and CD8+ T cells are stimulated with alphaCD3/alphaCD28 coated magnetic beads on day 0, and transduced with TFP on day 1 using a bicistronic lentiviral vector expressing TFP along with eGFP using a 2A ribosomal skipping sequence. Cultures are re-stimulated with either PD-1+K562 cells (K562-PD-1), wild-type K562 cells (K562 wild type) or K562 cells expressing hCD32 and 4-1BBL in the presence of antiCD3 and anti-CD28 antibody (K562-BBL-3/28) following washing. Exogenous IL-2 is added to the cultures every other day at 100 IU/mL. GFP+ T cells are enumerated by flow cytometry using bead-based counting (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Sustained TFP+ T-cell expansion in the absence of re-stimulation can also be measured (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Briefly, mean T-cell volume (fl) is measured on day 8 of culture using a Coulter Multisizer™ III particle counter following stimulation with alphaCD3/alphaCD28 coated magnetic beads on day 0, and transduction with the indicated TFP on day 1. 
     Animal models can also be used to measure TFP-T activity. For example, a xenograft model using human TAA-specific TFP+ T cells and/or PD-1 fusion protein+ T cells (e.g., PD1CD28+ T cells) to treat a cancer in immunodeficient mice (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Very briefly, after establishment of cancer, mice are randomized as to treatment groups. Different numbers of engineered T cells are coinjected at a 1:1 ratio into NOD/SCID/γ−/− mice bearing cancer. The number of copies of each vector in spleen DNA from mice is evaluated at various times following T-cell injection. Animals are assessed for cancer at weekly intervals. Peripheral blood TAA+ and/or PD-1+ cancer cell counts are measured in mice that are injected with alpha TAA-zeta TFP+ T cells or mock-transduced T cells. Survival curves for the groups are compared using the log-rank test. In addition, absolute peripheral blood CD4+ and CD8+ T-cell counts 4 weeks following T-cell injection in NOD/SCID/γ−/− mice can also be analyzed. Mice are injected with cancer cells and 3 weeks later are injected with T cells engineered to express TFP by a bicistronic lentiviral vector that encodes the TFP linked to eGFP. T cells are normalized to 45-50% input GFP+ T cells by mixing with mock-transduced cells prior to injection, and confirmed by flow cytometry. Animals are assessed for cancer at 1-week intervals. Survival curves for the TFP+ T-cell groups are compared using the log-rank test. 
     Dose dependent TFP treatment response can be evaluated (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). For example, peripheral blood is obtained 35-70 days after establishing cancer in mice injected on day 21 with TFP T cells, an equivalent number of mock-transduced T cells, or no T cells. Mice from each group are randomly bled for determination of peripheral blood TAA+ and/or PD-1+ cancer cell counts and then killed on days 35 and 49. The remaining animals are evaluated on days 57 and 70. 
     Assessment of cell proliferation and cytokine production has been previously described, e.g., at Milone et al., Molecular Therapy 17(8): 1453-1464 (2009). Briefly, assessment of TFP-mediated proliferation is performed in microtiter plates by mixing washed T cells with cells expressing PD-1 or CD32 and CD137 (KT32-BBL) for a final T-cell:cell expressing PD-1 ratio of 2:1. Cells expressing PD-1 cells are irradiated with gamma-radiation prior to use. Anti-CD3 (clone OKT3) and anti-CD28 (clone 9.3) monoclonal antibodies are added to cultures with KT32-BBL cells to serve as a positive control for stimulating T-cell proliferation since these signals support long-term CD8+ T-cell expansion ex vivo. T cells are enumerated in cultures using CountBright™ fluorescent beads (Invitrogen) and flow cytometry as described by the manufacturer. TFP+ T cells are identified by GFP expression using T cells that are engineered with eGFP-2A linked TFP-expressing lentiviral vectors. For TFP+ T cells not expressing GFP, the TFP+ T cells are detected with biotinylated recombinant PD-1 protein and a secondary avidin-PE conjugate. CD4+ and CD8+ expression on T cells are also simultaneously detected with specific monoclonal antibodies (BD Biosciences). Cytokine measurements are performed on supernatants collected 24 hours following re-stimulation using the human TH1/TH2 cytokine cytometric bead array kit (BD Biosciences) according the manufacturer&#39;s instructions. Fluorescence is assessed using a FACScalibur® flow cytometer, and data is analyzed according to the manufacturer&#39;s instructions. 
     Cytotoxicity can be assessed by a standard  51 Cr-release assay (see, e.g., Milone et al., Molecular Therapy 17(8): 1453-1464 (2009)). Briefly, target cells are loaded with  51 Cr (as NaCrO 4 , New England Nuclear) at 37° C. for 2 hours with frequent agitation, washed twice in complete RPMI medium and plated into microtiter plates. Effector T cells are mixed with target cells in the wells in complete RPMI at varying ratios of effector cell:target cell (E:T). Additional wells containing media only (spontaneous release, SR) or a 1% solution of Triton®-X 100 detergent (total release, TR) are also prepared. After 4 hours of incubation at 37° C., supernatant from each well is harvested. Released  51 Cr is then measured using a gamma particle counter (Packard Instrument Co., Waltham, Mass.). Each condition is performed in at least triplicate, and the percentage of lysis is calculated using the formula: % Lysis=(ER-SR)/(TR-SR), where ER represents the average  51 Cr released for each experimental condition. 
     Cytotoxicity may also be measured by a lactose dehydrogenase (LDH) assay. LDH colorimetric assay kits are available from, e.g., Thermo Scientific™ or Pierce™. The kit can be used with different cell types for measuring cytotoxicity mediated by chemical compounds as well as assaying cell-mediated cytotoxicity. Lactate dehydrogenase (LDH) is a cytosolic enzyme present in many different cell types. Plasma membrane damage releases LDH into the cell culture media. Extracellular LDH in the media can be quantified by a coupled enzymatic reaction in which LDH catalyzes the conversion of lactate to pyruvate via NAD+ reduction to NADH. Diaphorase then uses NADH to reduce a tetrazolium salt (INT) to a red formazan product that can be measured at 490 nm. The level of formazan formation is directly proportional to the amount of LDH released into the medium, which is indicative of cytotoxicity. Cultured cells are incubated with or effector cells (e.g., engineered T cells disclosed herein) to induce cytotoxicity and subsequently release LDH. The LDH released into the medium is transferred to a new plate and mixed with a reaction mixture provided in the kit. After a 30-minute room temperature incubation, reactions are stopped by adding a stop solution. Absorbance at 490 nm and 680 nm is measured using a plate-reading spectrophotometer to determine LDH activity. 
     Cytotoxicity may also be measured FACS and RTCA as described in the Examples below. 
     Imaging technologies can be used to evaluate specific trafficking and proliferation of TFPs in tumor-bearing animal models. Such assays have been described, e.g., in Barrett et al., Human Gene Therapy 22:1575-1586 (2011). Briefly, NOD/SCID/γc−/− (NSG) mice are injected IV with cancer cells followed 7 days later with T cells 4 hour after electroporation with the TFP constructs. The T cells are stably transfected with a lentiviral construct to express firefly luciferase, and mice are imaged for bioluminescence. Alternatively, therapeutic efficacy and specificity of a single injection of TFP+ T cells in a cancer xenograft model can be measured as follows: NSG mice are injected with cancer cells transduced to stably express firefly luciferase, followed by a single tail-vein injection of T cells electroporated with PD-1 TFP 7 days later. Animals are imaged at various time points post injection. For example, photon-density heat maps of firefly luciferase positive cancer in representative mice at day 5 (2 days before treatment) and day 8 (24 hours post TFP+ PBLs) can be generated. 
     Other assays, including those described in the Example section herein as well as those that are known in the art can also be used to evaluate the PD-1 TFP constructs of the invention. 
     Combination Therapies 
     A TFP-expressing cell and/or a PD-1 fusion protein-expressing cell (e.g., a PD1CD28-expressing cell) described herein may be used in combination with other known agents and therapies. Administered “in combination”, as used herein, means that two (or more) different treatments are delivered to the subject during the course of the subject&#39;s affliction with the disorder, e.g., the two or more treatments are delivered after the subject has been diagnosed with the disorder and before the disorder has been cured or eliminated or treatment has ceased for other reasons. In some embodiments, the delivery of one treatment is still occurring when the delivery of the second begins, so that there is overlap in terms of administration. This is sometimes referred to herein as “simultaneous” or “concurrent delivery”. In other embodiments, the delivery of one treatment ends before the delivery of the other treatment begins. In some embodiments of either case, the treatment is more effective because of combined administration. For example, the second treatment is more effective, e.g., an equivalent effect is seen with less of the second treatment, or the second treatment reduces symptoms to a greater extent, than would be seen if the second treatment were administered in the absence of the first treatment or the analogous situation is seen with the first treatment. In some embodiments, delivery is such that the reduction in a symptom, or other parameter related to the disorder is greater than what would be observed with one treatment delivered in the absence of the other. The effect of the two treatments can be partially additive, wholly additive, or greater than additive. The delivery can be such that an effect of the first treatment delivered is still detectable when the second is delivered. 
     In some embodiments, the at least one additional therapeutic agent comprises a PD-1 fusion protein as described above, e.g., a PD1CD28 fusion protein. In one embodiment, the PD-1 fusion protein may be expressed in the same T cell population as the TFP, and thus is administered to a patient simultaneously. In some embodiments, the PD-1 fusion protein is expressed in a second T cell population. The T cell population comprising the TFP and the T cell population comprising the PD-1 fusion protein may be administered simultaneously or sequentially. In some embodiments, combinations of cell-based therapeutics (e.g., human T cell therapeutics) are administered simultaneously. In some embodiments, combinations of cell-based therapeutics (e.g., human T cell therapeutics) and non-cell-based therapeutics (e.g., small molecule chemotherapeutics or antibody therapeutics) are administered sequentially. 
     In some embodiments, the “at least one additional therapeutic agent” includes a second TFP-expressing cell population that is targeted to a second tumor associated antigen. Also provided are T cells that express multiple TFPs, which bind to the same or different target antigens, or same or different epitopes on the same target antigen. Also provided are populations of T cells in which a first subset of T cells expresses a first TFP and a second subset of T cells express a second TFP. In one embodiment, the additional therapeutic agent is a TFP-expressing cell that expresses IL-12. 
     A TFP-expressing cell described herein and the at least one additional therapeutic agent can be administered simultaneously, in the same or in separate compositions, or sequentially. For sequential administration, the TFP-expressing cell described herein can be administered first, and the additional agent can be administered second, or the order of administration can be reversed. 
     In further aspects, a TFP-expressing cell described herein may be used in a treatment regimen in combination with surgery, chemotherapy, radiation, immunosuppressive agents such as cyclosporin, azathioprine, methotrexate, mycophenolate, and tacrolimus (FK506), or other immunoablative agents such as alemtuzumab, anti-CD3 antibodies or other antibody therapies, cyclophosphamide, fludarabine, cyclosporin, rapamycin, mycophenolic acid, steroids, romidepsin (FR901228), cytokines, and irradiation. A TFP-expressing cell described herein may also be used in combination with a peptide vaccine, such as that described in Izumoto et al. 2008 J Neurosurg 108:963-971. 
     In some embodiments, the subject can be administered an agent which reduces or ameliorates a side effect associated with the administration of a TFP-expressing cell. Side effects associated with the administration of a TFP-expressing cell include, but are not limited to cytokine release syndrome (CRS), and hemophagocytic lymphohistiocytosis (HLH), also termed Macrophage Activation Syndrome (MAS). Symptoms of CRS include high fevers, nausea, transient hypotension, hypoxia, and the like. Accordingly, the methods described herein can comprise administering a TFP-expressing cell described herein to a subject and further administering an agent to manage elevated levels of a soluble factor resulting from treatment with a TFP-expressing cell. In one embodiment, the soluble factor elevated in the subject is one or more of IFN-γ, TNFα, IL-2 and IL-6. Therefore, an agent administered to treat this side effect can be an agent that neutralizes one or more of these soluble factors. Such agents include, but are not limited to a steroid, an inhibitor of TNFα, and an inhibitor of IL-6. An example of a TNFα inhibitor is etanercept. An example of an IL-6 inhibitor is tocilizumab (toc). 
     In some embodiments, the subject can be administered an agent which enhances the activity of a TFP-expressing cell. For example, in one embodiment, the agent can be an agent which inhibits an inhibitory molecule. Inhibitory molecules, e.g., Programmed Death 1 (PD-1), can, in some embodiments, decrease the ability of a TFP-expressing cell to mount an immune effector response. Examples of inhibitory molecules include, but are not limited to, PD-1, PD-L1, CTLA-4, TIM3, LAG3, VISTA, BTLA, TIGIT, LAIR1, CD160, 2B4 and TGFR beta. 
     Inhibition of an inhibitory molecule, e.g., by inhibition at the DNA, RNA or protein level, can optimize a TFP-expressing cell performance. In embodiments, an inhibitory nucleic acid, e.g., an inhibitory nucleic acid, e.g., a dsRNA, e.g., an siRNA or shRNA, can be used to inhibit expression of an inhibitory molecule in the TFP-expressing cell. In an embodiment the inhibitor is a shRNA. In an embodiment, the inhibitory molecule is inhibited within a TFP-expressing cell. In these embodiments, a dsRNA molecule that inhibits expression of the inhibitory molecule is linked to the nucleic acid that encodes a component, e.g., all of the components, of the TFP. In one embodiment, the inhibitor of an inhibitory signal can be, e.g., an antibody or antibody fragment that binds to an inhibitory molecule. For example, the agent can be an antibody or antibody fragment that binds to PD-1, PD-L1, PD-L2 or CTLA-4 (e.g., ipilimumab (also referred to as MDX-010 and MDX-101, and marketed as Yervoy™; Bristol-Myers Squibb; tremelimumab (IgG2 monoclonal antibody available from Pfizer, formerly known as ticilimumab, CP-675,206)). In an embodiment, the agent is an antibody or antibody fragment that binds to TIM3. In an embodiment, the agent is an antibody or antibody fragment that binds to LAG3. 
     In some embodiments, the agent which enhances the activity of a TFP-expressing cell can be, e.g., a fusion protein comprising a first domain and a second domain, wherein the first domain is an inhibitory molecule, or fragment thereof, and the second domain is a polypeptide that is associated with a positive signal, e.g., a polypeptide comprising an intracellular signaling domain as described herein. In some embodiments, the polypeptide that is associated with a positive signal can include a co-stimulatory domain of CD28, CD27, ICOS, e.g., an intracellular signaling domain of CD28, CD27 and/or ICOS, and/or a primary signaling domain, e.g., of CD3 zeta, e.g., described herein. In one embodiment, the fusion protein is expressed by the same cell that expressed the TFP. In another embodiment, the fusion protein is expressed by a cell, e.g., a T-cell that does not express an anti-TAA TFP. 
     Pharmaceutical Compositions 
     Pharmaceutical compositions of the present invention may comprise a TFP-expressing cell, e.g., a plurality of TFP-expressing cells, as described herein, in combination with a PD-1 fusion protein (e.g., a PD1CD28 switch) expressing cell, e.g., a plurality of PD-1 fusion protein expressing cells, and one or more pharmaceutically or physiologically acceptable carriers, diluents or excipients. Such compositions may comprise buffers such as neutral buffered saline, phosphate buffered saline and the like; carbohydrates such as glucose, mannose, sucrose or dextrans, mannitol; proteins; polypeptides or amino acids such as glycine; antioxidants; chelating agents such as EDTA or glutathione; adjuvants (e.g., aluminum hydroxide); and preservatives. Compositions of the present invention are in one aspect formulated for intravenous administration. 
     Pharmaceutical compositions of the present invention may be administered in a manner appropriate to the disease to be treated (or prevented). The quantity and frequency of administration will be determined by such factors as the condition of the patient, and the type and severity of the patient&#39;s disease, although appropriate dosages may be determined by clinical trials. 
     In one embodiment, the pharmaceutical composition is substantially free of, e.g., there are no detectable levels of a contaminant, e.g., selected from the group consisting of endotoxin,  mycoplasma , replication competent lentivirus (RCL), p24, VSV-G nucleic acid, HIV gag, residual anti-CD3/anti-CD28 coated beads, mouse antibodies, pooled human serum, bovine serum albumin, bovine serum, culture media components, vector packaging cell or plasmid components, a bacterium and a fungus. In one embodiment, the bacterium is at least one selected from the group consisting of  Alcaligenes faecalis, Candida albicans, Escherichia coli, Haemophilus influenza, Neisseria meningitides, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumonia , and  Streptococcus pyogenes  group A. 
     When “an immunologically effective amount,” “an anti-tumor effective amount,” “a tumor-inhibiting effective amount,” or “therapeutic amount” is indicated, the precise amount of the compositions of the present invention to be administered can be determined by a physician with consideration of individual differences in age, weight, tumor size, extent of infection or metastasis, and condition of the patient (subject). It can generally be stated that a pharmaceutical composition comprising the T cells described herein may be administered at a dosage of 10 4  to 10 9  cells/kg body weight, in some instances 10 5  to 10 6  cells/kg body weight, including all integer values within those ranges. T-cell compositions may also be administered multiple times at these dosages. The cells can be administered by using infusion techniques that are commonly known in immunotherapy (see, e.g., Rosenberg et al., New Eng. J. of Med. 319:1676, 1988). 
     In certain aspects, it may be desired to administer activated T cells to a subject and then subsequently redraw blood (or have an apheresis performed), activate T cells therefrom according to the present invention, and reinfuse the patient with these activated and expanded T cells. This process can be carried out multiple times every few weeks. In certain aspects, T cells can be activated from blood draws of from 10 cc to 400 cc. In certain aspects, T cells are activated from blood draws of 20 cc, 30 cc, 40 cc, 50 cc, 60 cc, 70 cc, 80 cc, 90 cc, or 100 cc. 
     The administration of the subject compositions may be carried out in any convenient manner, including by aerosol inhalation, injection, ingestion, transfusion, implantation or transplantation. The compositions described herein may be administered to a patient trans arterially, subcutaneously, intradermally, intratumorally, intranodally, intramedullary, intramuscularly, by intravenous (i.v.) injection, or intraperitoneally. In one aspect, the T-cell compositions of the present invention are administered to a patient by intradermal or subcutaneous injection. In one aspect, the T-cell compositions of the present invention are administered by i.v. injection. The compositions of T cells may be injected directly into a tumor, lymph node, or site of infection. 
     In a particular exemplary aspect, subjects may undergo leukapheresis, wherein leukocytes are collected, enriched, or depleted ex vivo to select and/or isolate the cells of interest, e.g., T cells. These T-cell isolates may be expanded by methods known in the art and treated such that one or more TFP constructs of the invention may be introduced, thereby creating a TFP-expressing T-cell of the invention. Subjects in need thereof may subsequently undergo standard treatment with high dose chemotherapy followed by peripheral blood stem cell transplantation. In certain aspects, following or concurrent with the transplant, subjects receive an infusion of the expanded TFP T cells of the present invention. In an additional aspect, expanded cells are administered before or following surgery. 
     The dosage of the above treatments to be administered to a patient will vary with the precise nature of the condition being treated and the recipient of the treatment. The scaling of dosages for human administration can be performed according to art-accepted practices. The dose for alemtuzumab, for example, will generally be in the range 1 to about 100 mg for an adult patient, usually administered daily for a period between 1 and 30 days. The preferred daily dose is 1 to 10 mg per day although in some instances larger doses of up to 40 mg per day may be used (described in U.S. Pat. No. 6,120,766). 
     In one embodiment, the anti-TAA TFP and/or PD-1 fusion protein is introduced into T cells, e.g., using in vitro transcription, and the subject (e.g., human) receives an initial administration of TFP T cells of the invention, and one or more subsequent administrations of the TFP T cells of the invention, wherein the one or more subsequent administrations are administered less than 15 days, e.g., 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, or 2 days after the previous administration. In one embodiment, more than one administration of the TFP T cells of the invention are administered to the subject (e.g., human) per week, e.g., 2, 3, or 4 administrations of the TFP T cells of the invention are administered per week. In one embodiment, the subject (e.g., human subject) receives more than one administration of the TFP T cells per week (e.g., 2, 3 or 4 administrations per week) (also referred to herein as a cycle), followed by a week of no TFP T cells administrations, and then one or more additional administration of the TFP T cells (e.g., more than one administration of the TFP T cells per week) is administered to the subject. In another embodiment, the subject (e.g., human subject) receives more than one cycle of TFP T cells, and the time between each cycle is less than 10, 9, 8, 7, 6, 5, 4, or 3 days. In one embodiment, the TFP T cells are administered every other day for 3 administrations per week. In one embodiment, the TFP T cells of the invention are administered for at least two, three, four, five, six, seven, eight or more weeks. 
     In one aspect, PD-1 TFP T cells are generated using lentiviral viral vectors, such as lentivirus. TFP-T cells generated that way will have stable TFP expression. 
     In one aspect, TFP T cells transiently express TFP vectors for 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 days after transduction. Transient expression of TFPs can be effected by RNA TFP vector delivery. In one aspect, the TFP RNA is transduced into the T-cell by electroporation. 
     A potential issue that can arise in patients being treated using transiently expressing TFP T cells (particularly with murine scFv bearing TFP T cells) is anaphylaxis after multiple treatments. 
     Without being bound by this theory, it is believed that such an anaphylactic response might be caused by a patient developing humoral anti-TFP response, i.e., anti-TFP antibodies having an anti-IgE isotype. It is thought that a patient&#39;s antibody producing cells undergo a class switch from IgG isotype (that does not cause anaphylaxis) to IgE isotype when there is a ten to fourteen-day break in exposure to antigen. 
     If a patient is at high risk of generating an anti-TFP antibody response during the course of transient TFP therapy (such as those generated by RNA transductions), TFP T-cell infusion breaks should not last more than ten to fourteen days. 
     EXAMPLES 
     The invention is further described in detail by reference to the following experimental examples. These examples are provided for purposes of illustration only, and are not intended to be limiting unless otherwise specified. Thus, the invention should in no way be construed as being limited to the following examples, but rather, should be construed to encompass any and all variations which become evident as a result of the teaching provided herein. Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the compounds of the present invention and practice the claimed methods. The following working examples specifically point out various aspects of the present invention, and are not to be construed as limiting in any way the remainder of the disclosure. 
     Materials and Methods 
     Example 1: Cell Lines and Cell Culture Conditions 
     All cell lines are purchased from American Type Culture Collection (ATCC) unless otherwise noted. Representative examples of cell lines appropriate for use in the methods disclosed herein are listed below. The tumor cell lines described below express low levels of PD-L1 in the absence of IFNγ exposure. Thus, PD-L1 may also be lentivirally transduced into these cells lines to produce versions that have high stable expression of PD-L1. A tumor-associated antigen or control antigen may be transduced into these cell lines to test the fusion proteins disclosed herein; non-limiting examples are mesothelin (MSLN), BCMA, CD19, CD20, CD22, prostate specific cancer antigen (PSCA), and ROR-1. Any surface expressed tumor associated antigen that may be used as a target for the combination therapies disclosed herein may be substituted. 
     In some embodiments, a human mesothelioma cell lines may be used. Non-limiting examples are MSTO-211 and OVCAR3. If the natural expression of mesothelin on the cells is low, these cell lines can also be transduced with human mesothelin to increase the surface expression of mesothelin. Firefly luciferase is lentivirally transduced into the lines to produce MSTO-211ffluc and OVCAR3ffluc. 
     Nalm6 is a B-cell leukemia precursor cell line with high expression of CD19 (German DSMZ Cell Collection Cat #: ACC 128). Click beetle red (“CBG”) or firefly luciferase is lentivirally transduced into Nalm6 to produce Nalm6-CBG or NALM-6ffluc. 
     K562 is a chronic myelogenous leukemia cell line (ATCC; Cat #: CCL-243). In one embodiment, CD19 is lentivirally transduced into K562 to produce K562-CD19. Other targets may be transduced as appropriate. 
     Other exemplary tumor cell lines, such as Raji (ATCC® CCL86™), daudi (ATCC® CCL213TM) and those found in the NCI-60 panel, may be used. In addition, other immortalized laboratory cell lines, such as HeLa, HEK-293, etc. may be engineered to express proteins of interest for testing the fusion proteins disclosed herein. 
     Tumor cells and T cells are cultured in RPMI 1640 medium (Gibco, Cat #11875-085) supplemented with 10% heat-inactivated FCS, 100 U/mL penicillin, 100 mg/mL streptomycin sulfate, and 1% L-glutamine. 
     Generation of Fusion Proteins: T Cell Receptor Fusion Proteins (TFPs) 
     Generation of TFPs for use in combination with the PD1CD28 switch-receptor, as disclosed herein, is described, e.g., in co-pending International Non-Provisional Application Serial No. PCT/US2016/033146, filed May 18, 2016, and co-pending provisional Application Ser. No. 62/405,551, filed Oct. 7, 2016, 62/357,185, filed Jun. 30, 2016, 62/370,189, filed Aug. 2, 2016, 62/425,697, filed Nov. 23, 2016, 62/425,407, filed Nov. 22, 2016, 62/425,535, filed Nov. 22, 2016, and 62/425,884, filed Nov. 23, 2016, each of which is herein incorporated by reference. 
     Example 2: Generation of Fusion Proteins: A PD1CD28 Switch-Receptor 
     The PD1CD28 switch-receptor is constructed by fusing a truncated extracellular PD-1 (amino acids 1-155) derived from PD-1-cDNA (Origene) with the transmembrane and cytoplasmic domains of CD28 (amino acids 141-220). A mutated version of the PD switch-receptor is also constructed (PD1CD28m) wherein the CD28 signaling is abrogated as described in Liu et al., (2016) Cancer Res. 76(6), and described further in copending International Non-Provisional Application Serial No. PCT/EP2016/064195, filed Jun. 20, 2016, each herein incorporated by reference. 
     Example 3: Lentiviral Production 
     Lentivirus encoding the appropriate constructs are prepared according to the following procedure or minor variations thereof 5×10 6  HEK-293FT cells are seeded into a 100 mm dish and allowed to reach 70-90% confluency overnight. 2.5 μg of the indicated DNA plasmids and 20 μL Lentivirus Packaging Mix (ALSTEM, cat #VP100) are diluted in 0.5 mL DMEM or Opti-MEM® I Medium without serum and mixed gently. In a separate tube, 30 μL of NanoFect® transfection reagent (ALSTEM, cat #NF100) is diluted in 0.5 mL DMEM or Opti-MEM I Medium without serum and mixed gently. The NanoFect/DMEM and DNA/DMEM solutions are then mixed together and vortexed for 10-15 seconds prior to incubation of the DMEM-plasmid-NanoFect mixture at room temperature for 15 minutes. The complete transfection complex from the previous step is added dropwise to the plate of cells and rocked to disperse the transfection complex evenly in the plate. The plate is then incubated overnight at 37° C. in a humidified 5% CO2 incubator. The following day, the supernatant is replaced with 10 mL fresh media and supplemented with 20 μL of ViralBoost™ (500×, ALSTEM, cat #VB100). The plates are then incubated at 37° C. for an additional 24 hours. The lentivirus-containing supernatant is then collected into a 50 mL sterile, capped conical centrifuge tube and put on ice. After centrifugation at 3000 rpm for 15 minutes at 4° C., the cleared supernatant is filtered with a low-protein binding 0.45 μm sterile filter and virus is subsequently isolated by ultracentrifugation at 25,000 rpm (Beckmann, L8-70M) for 1.5 hours, at 4° C. The pellet is removed and re-suspended in DMEM media and lentivirus concentrations/titers are established by quantitative RT-PCR, using the Lenti-X qRT-PCR Titration kit (Clontech; catalog number 631235). Any residual plasmid DNA is removed by treatment with DNasel. The virus stock preparation is either used for infection immediately or aliquoted and stored at −80° C. for future use. 
     Example 4: PBMC Isolation 
     Peripheral blood mononuclear cells (PBMCs) are prepared from either whole blood or buffy coat. Whole blood is collected in 10 mL Heparin vacutainers and either processed immediately or stored overnight at 4° C. Approximately 10 mL of whole anti-coagulated blood is mixed with sterile phosphate buffered saline (PBS) buffer for a total volume of 20 mL in a 50 mL conical centrifuge tube (PBS, pH 7.4, without Ca 2+ /Mg 2+ ). 20 mL of this blood/PBS mixture is then gently overlaid onto the surface of 15 mL of Ficoll-Paque® PLUS (GE Healthcare, 17-1440-03) prior to centrifugation at 400 g for 30-40 min at room temperature with no brake application. 
     Buffy coat is purchased, e.g., from Research Blood Components (Boston, Mass.). LeucoSep® tubes (Greiner bio-one) are prepared by adding 15 mL Ficoll-Paque® (GE Health Care) and centrifuged at 1000 g for 1 minute. Buffy coat is diluted 1:3 in PBS (pH 7.4, without Ca 2+  or Mg 2+ ). The diluted buffy coat is transferred to LeucoSep tube and centrifuged at 1000 g for 15 minutes with no brake application. The layer of cells containing PBMCs, seen at the diluted plasma/Ficoll® interface, is removed carefully to minimize contamination by Ficoll. Residual Ficoll, platelets, and plasma proteins are then removed by washing the PBMCs three times with 40 mL of PBS by centrifugation at 200 g for 10 minutes at room temperature. The cells are then counted with a hemocytometer. The washed PBMC are washed once with CAR-T media (AIM V-AlbuMAX® (BSA) (Life Technologies), with 5% AB serum and 1.25 μg/mL amphotericin B (Gemini Bioproducts, Woodland, Calif.), 100 U/mL penicillin, and 100 μg/mL streptomycin). Alternatively, the washed PBMC&#39;s are transferred to insulated vials and frozen at −80° C. for 24 hours before storing in liquid nitrogen for later use. 
     Example 5: T Cell Activation 
     PBMCs prepared from either whole blood or buffy coat are stimulated with anti-human CD28 and CD3 antibody-conjugated magnetic beads for 24 hours prior to viral transduction. Freshly isolated PBMCs are washed once in CAR-T medium (AIM V-AlbuMAX (BSA) (Life Technologies), with 5% AB serum and 1.25 μg/mL amphotericin B (Gemini Bioproducts), 100 U/mL penicillin, and 100 μg/mL streptomycin) without huIL-2, before being re-suspended at a final concentration of 1×10 6  cells/mL in CAR-T medium with 300 IU/mL human IL-2 (from a 1000× stock; Invitrogen). If the PBMCs had previously been frozen they are thawed and re-suspended at 1×10 7  cells/mL in 9 mL of pre-warmed (37° C.) DMEM medium (Life Technologies), in the presence of 10% FBS, 100 U/mL penicillin, and 100 μg/mL streptomycin, at a concentration of 1×10 6 cells/mL prior to washing once in CAR-T medium, re-suspension at 1×10 6  cells/mL in CAR-T medium, and addition of IL-2 as described above. 
     Prior to activation, anti-human CD28 and CD3 antibody-conjugated magnetic beads (available from, e.g., Invitrogen, Life Technologies) are washed three times with 1 mL of sterile 1×PBS (pH 7.4), using a magnetic rack to isolate beads from the solution, before re-suspension in CAR-T medium, with 300 IU/mL human IL-2, to a final concentration of 4×10 7  beads/mL. PBMC and beads are then mixed at a 1:1 bead-to-cell ratio, by transferring 25 μL (1×10 6  beads) of beads to 1 mL of PBMC. The desired number of aliquots are then dispensed to single wells of a 12-well low-attachment or non-treated cell culture plate, and incubated at 37° C., with 5% CO2, for 24 hours before viral transduction. 
     Example 6: T Cell Transduction/Transfection and Expansion 
     Following activation of PBMCs, cells are incubated for 48 hours at 37° C., 5% CO2. Lentivirus is thawed on ice and 5×10 6  lentivirus, along with 2 μL of TransPlus™ (Alstem) per mL of media (a final dilution of 1:500) is added to each well of 1×10 6  cells. Cells are incubated for an additional 24 hours before repeating addition of virus. Alternatively, lentivirus is thawed on ice and the respective virus is added at 5 or 50 MOI in presence of 5 μg/mL polybrene (Sigma). Cells are spinoculated at 100 g for 100 minutes at room temperature. Cells are then grown in the continued presence of 300 IU/mL of human IL-2 for a period of 6-14 days (total incubation time is dependent on the final number of TFP-T cells required). Cell concentrations are analyzed every 2-3 days, with media being added at that time to maintain the cell suspension at 1×10 6  cells/mL. 
     In some instances, activated PBMCs are electroporated with in vitro transcribed (IVT) mRNA. In one embodiment, human PBMCs are stimulated with DynaBeads® (ThermoFisher) at 1-to-1 ratio for 3 days in the presence of 300 IU/ml recombinant human IL-2 (R&amp;D Systems) (other stimulatory reagents such as TransAct® T Cell Reagent from Milyeni Pharmaceuticals may be used). The beads are removed before electroporation. The cells are washed and re-suspended in OPTI-MEM medium (ThermoFisher) at the concentration of 2.5×10 7  cells/mL. 200 μL of the cell suspension (5×10 6  cells) are transferred to the 2 mm gap Electroporation Cuvettes Plus™ (Harvard Apparatus BTX) and prechilled on ice. 10 μg of IVT TFP mRNA is added to the cell suspension. The mRNA/cell mixture is then electroporated at 200 V for 20 milliseconds using ECM830 Electro Square Wave Porator (Harvard Apparatus BTX) Immediately after the electroporation, the cells are transferred to fresh cell culture medium (AIM V AlbuMAX (BSA) serum free medium+5% human AB serum+300 IU/ml IL-2) and incubated at 37° C. 
     Example 7: Detection of TFP Expression by Cell Staining 
     Following lentiviral transduction or mRNA electroporation, expression of the TFP and the PD1CD28 switch-receptor is confirmed by flow cytometry. TFP incorporation into the T cell receptor may be detected by using the appropriate anti-target antibody (e.g., expression of a CD19-specific TFP may be detected with an anti-CD19 scFv antibody or anti-mouse Fab serum); detection of the PD1CD28 switch-receptor may be detected using an anti-PD-1 antibody or PD-L1-Fc to detect human PD-1. T cells are washed three times in 3 mL staining buffer (PBS, 4% BSA) and re-suspended in PBS at 1×10 6  cells per well. For dead cell exclusion, cells are incubated with LIVE/DEAD® Fixable Aqua Dead Cell Stain (Invitrogen) for 30 minutes on ice. Cells are washed twice with PBS and re-suspended in 50 μL staining buffer. To block Fc receptors, 1 μL of 1:100 diluted normal goat IgG (BD Bioscience) is added to each tube and incubated in ice for 10 minutes. 1.0 mL FACS buffer is added to each tube, mixed well, and cells are pelleted by centrifugation at 300 g for 5 min Surface expression of scFv TFPs is detected by Zenon® R-Phycoerythrin-labeled human anti-tumor antigen IgG1 Fc or tumor antigen-Fc. 1 μg antibodies or soluble tumor antigen is added to the respective samples and incubated for 30 minutes on ice. Cells are then washed twice, and T cells stained for surface markers using anti-CD3 APC (clone, UCHT1), anti-CD4-Pacific blue (Clone RPA-T4), anti-CD8 APCCy7 (Clone SK1), from BD bioscience. Flow cytometry is performed using LSRFortessa® X20 (BD Biosciences) and data are acquired using FACSDiva™ software and is analyzed with FlowJo® (Treestar, Inc. Ashland, Oreg.). 
     In one embodiment, T cells are transduced with an anti-BCMA TFP and a PD1CD28 switch-receptor. In another embodiment, T cells are transduced with an anti-MSLN TFP and a PD1CD28 switch-receptor. TFPs having antibodies to other target antigens may be successfully combined with the PD switch-receptor. Non-limiting examples of target antigens include, but are not limited to, Exemplary results will show the surface expression analysis of activated PBMC cells stained for CD8 (anti-CD8 APCCy7), the target antigen, e.g., BCMA (Zenon® R-Phycoerythrin-labeled hBCMA IgG), and PD-1 (labeled recombinant human PD-L1 or anti-PD-1). 
     Example 8: Cytotoxicity Assay by Flow Cytometry 
     Target cells that are either positive or negative for PD-1 ligand (i.e., PD-L1 and/or PD-L2) and the target tumor antigen (e.g., BCMA, CD19, MSLN etc.) are labelled with the fluorescent dye, carboxyfluorescein diacetate succinimidyl ester (CFSE). These target cells are mixed with effector T cells that are either un-transduced, transduced with the PD switch-receptor alone, a TFP specific to a tumor-associated antigen (e.g., a TFP specific to CD19), transduced with the mutated PD1CD28 switch-receptor, or transduced with TFPs and in combination with either the PD switch-receptor or the mutant PD1CD28m switch-receptor. After the indicated incubation period, the percentage of dead to live CFSE-labeled target cells and negative control target cells is determined for each effector/target cell culture by flow cytometry. The percent survival of target cells in each T cell-positive target cell culture is calculated relative to wells containing target cells alone. 
     The cytotoxic activity of effector T cells is measured by comparing the number of surviving target cells in target cells without or with effector T cells, following co-incubation of effector and target cells, using flow cytometry. In experiments with PD-1 switch-receptors in combination with anti-tumor antigen TFP cells, the target cells are tumor antigen-positive cells, while cells used as a negative control are tumor antigen-negative cells or PD-L1/PD-L2 negative cells. 
     In one embodiment, the target cells express CD19 on the cell surface and the combination therapy comprises an anti-CD19-TFP and a PD1CD28 switch-receptor. An exemplary method is as follows. Target cells are washed once, and re-suspended in PBS at 1×10 6  cells/mL. The fluorescent dye carboxyfluorescein diacetate succinimidyl ester (CFSE) (ThermoFisher®) is added to the cell suspension at a concentration of 0.03 μM and the cells are incubated for 20 minutes at room temperature. The labeling reaction is stopped by adding to the cell suspension complete cell culture medium (RPMI-1640+10% HI-FBS) at the volume 5 times of the reaction volume, and the cells are incubated for an additional two minutes at room temperature. The cells are pelleted by centrifugation and re-suspended in cytotoxicity medium (Phenol red-free RPMI1640 (Invitrogen) plus 5% AB serum (Gemini Bioproducts) at 2×10 5  cells/mL. Fifty microliters of CFSE labelled-target cell suspension (equivalent to 10,000 cells) are added to each well of the 96-well U-bottom plate (Corning). 
     Effector T cells transduced with TFP constructs (e.g., anti-CD19 TFP constructs) and the PD1CD28 fusion construct (i.e., co-expressing both constructs), together with non-transduced T cells as negative controls, are washed and suspended at 2×10 6  cells/mL, or 1×10 6  cells/mL in cytotoxicity medium. 50 μL of effector T cell suspensions (equivalent to 100,000 or 50,000 cells) are added to the plated target cells, e.g., Nalm6 and Nalm6-PDL1 cells, to reach the effector-to-target ratio of 10-to-1 or 5-to-1, respectively, in a total volume of 100 μL. The cultures are then mixed, spun down, and incubated for eight hours at 37° C. and 5% CO 2  Immediately following this incubation, 7AAD (7-aminoactinomycin D) (BioLegend) is added to the cultured cells as recommended by the manufacturer, and flow cytometry is performed with a BD LSRFortessa™ X-20 (BD Biosciences). Analysis of flow cytometric data is performed using FlowJo® software (TreeStar, Inc.). 
     The percentage of survival for the target cells expressing the tumor antigen (e.g., CD19) is calculated by dividing the number of live target cells (CFSE+7-AAD-) in a sample with effector T cells and target cells, by the number of live (CFSE+7-AAD-) cells in the sample with target cells alone. The cytotoxicity for effector cells is calculated as the percentage of killing for target cells=100%−percentage of survival for the cells. 
     T cells transduced with the PD1CD28 switch-receptor and a tumor antigen-specific TFP construct (e.g., an anti-CD19-TFP construct) will demonstrate cytotoxicity against tumor antigen-expressing cells (e.g., CD19-expressing Nalm6 cells and/or Nalm6-PDL1 cells) when compared to T cells that are either non-transduced or are transduced with a non-tumor antigen-specific TFP control. 
     T cells electroporated with mRNA encoding TFPs specific for CD19 and the PD1CD28 switch-receptor will demonstrate the highest cytotoxicity against, e.g., CD19-expressing Nalm6-PDL1 cells. A lower amount of killing will be seen for CD19-positive Nalm6 cells, and no significant killing of the CD19-negative Nalm6 cells (PD-L1-negative) cells may be seen with either control or the combination therapy disclosed herein, CD19-specific killing of CD19/PD-L1 (or PD-L2)-expressing cells may be observed, e.g., by T cells transduced with either PD-1-CD3ε, or PD-1-CD3γ TFPs. 
     Example 9: Method of Determining Cytotoxicity by Real Time Cytotoxicity Assay 
     As demonstrated in Example 1, T cells transduced with anti-tumor antigen TFPs+a PD1CD28 switch-receptor may also demonstrate superior cytotoxicity in a real-time cytotoxicity assay (RTCA) format. The RTCA assay measures the electrical impedance of an adherent target cell monolayer, in each well of a specialized 96-well plate, in real time and presents the final readout as a value called the cell index. Changes in cell index indicate disruption of the target cell monolayer as a result of killing of target cells by co-incubated T cell effectors. Thus, the cytotoxicity of the effector T cells can be evaluated as the change in cell index of wells with both target cells and effector T cells compared to that of wells with target cells alone. 
     Adherent target cells are cultured in DMEM, 10% FBS, 1% Antibiotic-Antimycotic (Life Technologies). To prepare the RTCA, 50 μL of, e.g., DMEM medium is added into the appropriate wells of an E-plate (ACEA Biosciences, Inc, Catalog #: JL-10-156010-1A). The plate is then placed into a RTCA MP instrument (ACEA Biosciences, Inc.) and the appropriate plate layout and assay schedule entered into the RTCA 2.0 software as described in the manufacturers manual. Baseline measurement is performed every 15 minutes for 100 measurements. 1×10 4  target cells in a 100 μL volume are then added to each assay well and the cells are allowed to settle for 15 minutes. The plate is returned to the reader and readings are resumed. 
     The next day, effector T cells are washed and re-suspended in cytotoxicity media (Phenol red-free RPMI1640 (Invitrogen) plus 5% AB serum (Gemini Bioproducts; 100-318)). The plate is then removed from the instrument and the effector T cells, suspended in cytotoxicity medium (Phenol red-free RPMI1640+5% AB serum), are added to each well at 100,000 cells or 50,000 cells to reach the effector-to-target ratio of 10-to-1 or 5-to-1, respectively. The plate is then placed back to the instrument. The measurement is carried out for every 2 minutes for 100 measurements, and then every 15 minutes for 1,000 measurements. 
     In some embodiments, the tumor antigen expressed on the surface of target cells is, e.g., MSLN. In the RTCA assay, killing of PD-L1− and MSLN-expressing cells may be observed by T cells transduced with PD1CD28 switch-receptor+anti-MSLN TFP as demonstrated by a time-dependent decrease in the cell index following addition of the effector cells relative to cells alone or cells co-incubated with T cells transduced with a control CAR construct. For example, within 4 hours of addition of T cells transduced with anti-MSLN-CD3ε TFP, killing of the MSLN-positive, PD-L1-expressing target cells may be essentially complete. Little or no killing may be observed with T cells transduced with a number of TFP constructs comprising other CD3 and TCR constructs. Cytotoxicity against MSLN/PD-L1 expressing target cells will be greater with anti-MSLN TFP-+ the PD1CD28 switch-receptor-transduced T cells than with T cells transduced with either the TFP or the switch receptor alone. Cytotoxicity against MSLN-positive, PD-L1 negative cells will be lower as it is dependent in that case on the TFP alone. 
     An anti-MSLN TFP construct is engineered by cloning a MSLN scFv DNA fragment linked to a CDR DNA fragment by a DNA sequence coding the linker: GGGGSGGGGSGGGGSLE (SEQ ID NO:1) into a p526 vector (from SBI) at XbaI and EcoRI sites. 
     Target cells for the RTCA are, e.g., MSLN-positive/PD-L1-positive cells, and the following control cell populations: MSLN−/PD-L1+ cells, MSLN+/PD-L1− cells, and MSLN−/PD-L1− cells are all used as negative controls. Adherent target cells are cultured in DMEM with 10% FBS and 1% Antibiotic-Antimycotic (Life Technologies). 
     The normalized cell index, indicative of cytotoxicity, is then determined. Activated PBMCs are untreated, non-transduced, or transduced with empty vector, transduced with anti-MSLN-TFP alone, transduced with PD1CD28 switch-receptor alone, or the combination of the anti-MSLN TFP+PD1CD28 switch-receptor, the anti-MSLN TFP alone, the PD1CD28 switch-receptor alone. Target cells are PD-L1-positive, with PD-L1-negative cells used as negative controls. 
     The target MSLN-positive cells are efficiently killed by the combination-transduced T cells, compared to the singly transduced cells or the negative controls. In contrast, the MSLN-negative cells are not efficiently killed by any of the constructs. 
     Example 10: Human TFP T Cell Treatment in an In Vivo Solid Tumor Xenograft Mouse Model 
     The efficacy of treatment with the combination therapies disclosed herein can be tested in immune compromised mouse models bearing subcutaneous solid tumors or disseminated or subcutaneous hematological tumors using tumor antigen-expressing human cancer cell lines. Tumor shrinkage in response to treatment with human TFP T cells and the PD-1 fusion receptor can be either assessed by caliper measurement of tumor size or by following the intensity of a luciferase protein (ffluc) signal emitted by ffluc-expressing tumor cells. 
     Primary human solid tumor cells can be grown in immune compromised mice without having to culture them in vitro. Exemplary solid cancer cells include solid tumor cell lines, such as provided in The Cancer Genome Atlas (TCGA) and/or the Broad Cancer Cell Line Encyclopedia (CCLE, see Barretina et al., Nature 483:603 (2012)). Exemplary solid cancer cells include primary tumor cells isolated from lung cancer, ovarian cancer, melanoma, colon cancer, gastric cancer, renal cell carcinoma, esophageal carcinoma, glioma, urothelial cancer, retinoblastoma, breast cancer, Non-Hodgkin lymphoma, pancreatic carcinoma, Hodgkin&#39;s lymphoma, myeloma, hepatocellular carcinoma, leukemia, cervical carcinoma, cholangiocarcinoma, oral cancer, head and neck cancer, or mesothelioma. These mice can be used to test the efficacy of T cells expressing the engineered T cell receptor and the PD1CD28 switch-receptor in the human tumor xenograft models. Following an implant or injection of 1×10 5 -1×10 7  primary cells (collagenase-treated bulk tumor suspensions in EC matrix material) or tumor fragments (primary tumor fragments in EC matrix material) subcutaneously, tumors are allowed to grow to 200-500 mm 3  prior to initiation of treatment. 
     Example 11: IL-2 and IFN-γ Secretion by ELISA 
     Another measure of effector T cell activation and proliferation associated with the recognition of cells bearing the cognate antigen is the production of effector cytokines such as interleukin-2 (IL-2) and interferon-gamma (IFN-γ). 
     ELISA assays for human IL-2 (catalog #EH2IL2, Thermo Scientific®) and IFN-γ catalog #KHC4012, Invitrogen) are performed as described in the product inserts. In one example, 50 μL of reconstituted standards or samples in duplicate are added to each well of a 96-well plate followed by 50 μL of Biotinylated Antibody Reagent. Samples are mixed by gently tapping the plate several times. 50 μL of Standard Diluent is then added to all wells that did not contain standards or samples and the plate is carefully sealed with an adhesive plate cover prior to incubation for 3 hours at room temperature (20-25° C.). The plate cover is then removed, plate contents are emptied, and each well is filled with Wash Buffer. This wash procedure is repeated a total of 3 times and the plate is blotted onto paper towels or other absorbent material. 100 μL of prepared Streptavidin-HRP Solution is added to each well and a new plate cover is attached prior to incubation for 30 minutes at room temperature. The plate cover is again removed, the plate contents are discarded, and 100 μL of TMB Substrate Solution is added into each well. The reaction is allowed to develop at room temperature in the dark for 30 minutes, after which 100 μL of Stop Solution is added to each well. Evaluate the plate. Absorbance is measured on an ELISA plate reader set at 450 nm and 550 nm within 30 minutes of stopping the reaction. 550 nm values are subtracted from 450 nm values and IL-2 amounts in unknown samples are calculated relative to values obtained from an IL-2 standard curve. 
     Alternatively, 2-Plex assays are performed using the Human Cytokine Magnetic Buffer Reagent Kit (Invitrogen, LHB0001M) with the Human IL-2 Magnetic Bead Kit (Invitrogen, LHC0021M) and the Human IFN-γ Magnetic Bead Kit (Invitrogen, LHC4031M). Briefly, 25 μL of Human IL-2 and IFN-γ antibody beads are added to each well of a 96-well plate and washed using the following guidelines: two washes of 200 μL 1× wash solution, placing the plate in contact with a Magnetic 96-well plate Separator (Invitrogen, A14179), letting the beads settle for 1 minute and decanting the liquid. Then, 50 μL of Incubation Buffer is added to each well of the plate with 100 μL of reconstituted standards in duplicates or 50 μL of samples (supernatants from cytotoxicity assays) and 50 μL of Assay Diluent, in triplicate, for a total volume of 150 μL. Samples are mixed in the dark at 600 rpm with an orbital shaker with a 3 mm orbital radius for 2 hours at room temperature. The plate is washed following the same washing guidelines and 100 μL of human IL-2 and IFN-γ biotinylated detector antibody is added to each well. Samples are mixed in the dark at 600 rpm with an orbital shaker with a 3 mm orbital radius for 1 hour at room temperature. The plate is washed following the same washing guidelines and 100 μL of Streptavidin-R-Phycoerythrin is added to each well. Samples are mixed in the dark at 600 rpm with an orbital shaker with a 3 mm orbital radius for 30 minutes at room temperature. The plate is washed 3 times using the same washing guidelines and after decanting the liquid the samples are re-suspended in 150 μL of 1× wash solution. The samples are mixed at 600 rpm with an orbital shaker with a 3 mm orbital radius for 3 minutes and stored over night at 4° C. Afterwards, the plate is washed following the same washing guidelines and the samples are re-suspended in 150 μL of 1× wash solution. 
     The plate is read using the MAGPIX System (Luminex) and xPONENT software. Analysis of the data is performed using MILLIPLEX Analyst software, which provides the standard curve and cytokine concentrations. 
     Relative to non-transduced or control singly-transduced T cells (i.e., T cells transduced with either the TFP or the switch-receptor alone), T cells transduced with tumor-antigen-specific TFPs and the PD switch-receptor alone may produce higher levels of both IL-2 and IFN-γ when co-cultured with either cells that endogenously express the tumor antigen or tumor antigen-transduced cells. In contrast, co-culture with tumor antigen-negative cells or non-transduced cells may result in little or no cytokine release from TFP-transduced T cells. 
     Anti-tumor antigen-CDR and anti-tumor antigen-CD3γ may produce the highest IL-2 and IFN-γ levels of the TFP constructs. However, cytokine production by T cells transduced with anti-tumor antigen-CD3ε or anti-tumor antigen-CD3γ TFPs (e.g., anti-CD19-CD3ε or anti-CD19-CD3γ TFPs) and the PD1CD28 switch-receptor may be comparable in the ability to kill PD-L1 negative target cells T cells expressing the TFP only. 
     Activated PBMCs are transduced with 50 MOI lentiviruses for two consecutive days and expanded. Day 8 post transduction, co-cultures of PBMCs were set up with target cells (K562 cells expressing PD-L1 and the anti-tumor antigen, such as CD19, “K562-19-PD-L1”, or PD-L1 negative K562-19, or CD19 negative K562-PD-L1) at E:T, 1:1 ratio (0.2×10 6  each cell type) in cytotoxicity medium (Phenol red-free RPMI1640 (Invitrogen) plus 5% AB serum (Gemini Bioproducts; 100-318). PD-L1-expressing K562 cells overexpressing a different tumor-associated antigen, e.g., BCMA, may be used as negative controls. After 24 hours, cells are analyzed for IFN-γ and IL-2 expression by ELISA as described above. In one example, T cells expressing PD fusion proteins and CD19 TFP constructs are activated, as evidenced by both IFN-γ and IL-2 production, by co-culturing with K562-19-D-L1 further demonstrating the ability of PD-1-expressing cells to specifically activate T cells. 
     Example 12: In Vivo Mouse Efficacy Studies 
     To assess the ability of effector T cells transduced with anti-tumor-antigen TFPs, e.g., anti-MSLN TFPs, to achieve anti-tumor responses in vivo, effector T cells transduced with either 1) anti-MSLN TFP+PD1CD28 switch-receptor, 2) anti-MSLN TFP alone, 3) PD1CD28 switch-receptor alone, or 4) non-transduced, are adoptively transferred into NOD/SCID/IL-2Rγ−/− (NSG-JAX) mice that had previously been inoculated with a PD-L1+ or a PD-L1− human cancer cell line. 
     Female NOD/SCID/IL-2Rγ−/− (NSG-JAX) mice, at least 6 weeks of age prior to the start of the study, are obtained from The Jackson Laboratory and acclimated for 3 days before experimental use. Human cancer cell lines for inoculation are maintained in log-phase culture prior to harvesting and counting with trypan blue to determine a viable cell count. On the day of tumor challenge, the cells are centrifuged at 300 g for 5 minutes and re-suspended in pre-warmed sterile PBS at either 0.5-1×10 6  cells/100 μL. T cells for adoptive transfer, either non-transduced, transduced with the TFP alone, transduced with the PD1CD28 switch alone, or co-transduced with both the TFP and the PD switch-receptor, are prepared. On day 0 of the study, 10 animals per experimental group are challenged intravenously with 0.5-1×10 6  cancer cells. 3 days later, 5×10 6  of effector T cell populations are intravenously transferred to each animal in 100 μL of sterile PBS. Detailed clinical observations on the animals are recorded daily until euthanasia. Body weight measurements are made on all animals weekly until death or euthanasia. All animals are euthanized 35 days after adoptive transfer of test and control articles. Any animals appearing moribund during the study are euthanized at the discretion of the study director in consultation with a veterinarian. 
     A summary of expected results is shown in Table 1. Relative to non-transduced T cells or singly transduced T cells, adoptive transfer of T cells transduced with the combination or anti-tumor antigen TFP constructs+the PD switch receptor may prolong survival of PD-L1+ or PD-L2+ tumor-bearing mice, and may indicate that combination therapies comprising both TFP-transduced T cells and the PD switch receptor are capable of mediating target cell killing with corresponding increased survival in these mouse models. Collectively, these data will indicate that combination therapies comprising PD1CD28 switch-receptors and anti-tumor-antigen TFPs represent an alternative platform for engineering chimeric receptors that demonstrate superior antigen-specific killing both in vitro and in vivo. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Tumor growth inhibition in vivo by adoptive 
               
               
                 transfer of co-transduced MSLN+ T cells 
               
            
           
           
               
               
               
            
               
                   
                 PD1+ cell 
                 PD1− cell 
               
               
                 T-cells: 
                 inoculation 
                 inoculation 
               
               
                   
               
               
                 non-transduced 
                 no tumor growth 
                 no tumor growth 
               
               
                   
                 inhibition 
                 inhibition 
               
               
                 anti-MSLN TFP 
                 Some tumor growth 
                 some tumor growth 
               
               
                 transduced 
                 inhibition, can be lower 
                 inhibition 
               
               
                   
                 relative to PD1− 
               
               
                   
                 cell inoculation 
               
               
                 PD1CD28 switch- 
                 no tumor growth 
                 no tumor growth 
               
               
                 receptor transduced 
                 inhibition 
                 inhibition 
               
               
                 Co-transduced with 
                 higher tumor growth 
                 some tumor growth 
               
               
                 anti-MSLN TFP + 
                 inhibition relative to 
                 inhibition 
               
               
                 PD1CD28 switch- 
                 PD1− cell inoculation 
               
               
                 receptor 
               
               
                   
               
            
           
         
       
     
     Example 13: Combination Therapies Comprising PD-1 Switch-Receptors and TFPs 
     In some embodiments, the combination therapy comprises an additional antibody. In one embodiment, the PD-1 switch-receptor is administered in combination with a TFP comprising a CD16 polypeptide and an IgG1 antibody to a tumor antigen on the surface of the target cell. For example, T cells are transduced with the CD16-CD3ε TFP+ the PD1CD28 switch-receptor. These T cells are then administered to a subject and the subject receives an IgG anti-tumor antibody, e.g., rituximab. In some embodiments, the TFPs in the combination therapy are dual specificity TFPs. Such TFPs comprise two scFv polypeptides, expressed in tandem attached to a single TCR subunit, or each expressed on different subunits. For example, a TFP may comprise an anti-CD19 scFv-CD3ε construct and an anti-BCMA scFv-CD3γ construct. Other antigen-binding pairs may be used, such as those comprising antibodies to CD20, CD22, ROR1, MSLN, BCMA, CD19, and the like. The dual specificity TFPs are administered in combination with the PD-1 switch-receptors as described above. 
     While preferred embodiments of the present invention 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 invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby. 
     
       
         
           
               
            
               
                   
               
               
                 APPENDIX A: SEQUENCE SUMMARY 
               
            
           
           
               
               
               
            
               
                 SEQ 
                   
                   
               
               
                 ID 
                   
                   
               
               
                 NO. 
                 NAME 
                 SEQUENCE 
               
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 Short Linker 1 
                 GGGGSGGGGSGGGGSLE 
               
               
                   
               
               
                 2 
                 Short Linker 2 
                 AAAGGGGSGGGGSGGGGSLE 
               
               
                   
               
               
                 3 
                 Long Linker  
                 AAAIEVMYPPPYLGGGGSGGGGSGGGGSLE 
               
               
                   
               
               
                 4 
                 human CD3-ϵ 
                 MQSGTHWRVLGLCLLSVGVWGQDGNEEMGGITQTPYKVSISGTTVILT 
               
               
                   
                   
                 CPQYPGSEILWQHNDKNIGGDEDDKNIGSDEDHLSLKEFSELEQSGYY 
               
               
                   
                   
                 VCYPRGSKPEDANFYLYLRARVCENCMEMDVMSVATIVIVDICITGGL 
               
               
                   
                   
                 LLLVYYWSKNRKAKAKPVTRGAGAGGRQRGQNKERPPPVPNPDYEPI 
               
               
                   
                   
                 RKGQRDLYSGLNQRRI 
               
               
                   
               
               
                 5 
                 human CD3-γ 
                 MEQGKGLAVLILAIILLQGTLAQSIKGNHLVKVYDYQEDGSVLLTCDA 
               
               
                   
                   
                 EAKNITWFKDGKMIGFLTEDKKKWNLGSNAKDPRGMYQCKGSQNKS 
               
               
                   
                   
                 KPLQVYYRMCQNCIELNAATISGFLFAEIVSIFVLAVGVYFIAGQDGVR 
               
               
                   
                   
                 QSRASDKQTLLPNDQLYQPLKDREDDQYSHLQGNQLRRN 
               
               
                   
               
               
                 6 
                 human CD3-δ 
                 MEHSTFLSGLVLATLLSQVSPFKIPIEELEDRVFVNCNTSITWVEGTVGT 
               
               
                   
                   
                 LLSDITRLDLGKRILDPRGIYRCNGTDIYKDKESTVQVHYRMCQSCVEL 
               
               
                   
                   
                 DPATVAGIIVTDVIATLLLALGVFCFAGHETGRLSGAADTQALLRNDQ 
               
               
                   
                   
                 VYQPLRDRDDAQYSHLGGNWARNKS 
               
               
                   
               
               
                 7 
                 human CD3-ζ 
                 MKWKALFTAAILQAQLPITEAQSFGLLDPKLCYLLDGILFIYGVILTALF 
               
               
                   
                   
                 LRVKFSRSADAPAYQQGQNQLYNELNLGRREEYDVLDKRRGRDPEMG 
               
               
                   
                   
                 GKPQRRKNPQEGLYNELQKDKMAEAYSEIGMKGERRRGKGHDGLYQ 
               
               
                   
                   
                 GLSTATKDTYDALHMQALPPR 
               
               
                   
               
               
                 8 
                 human TCR  
                 MAGTWLLLLLALGCPALPTGVGGTPFPSLAPPIMLLVDGKQQMVVVC 
               
               
                   
                 α-chain 
                 LVLDVAPPGLDSPIWFSAGNGSALDAFTYGPSPATDGTWTNLAHLSLP 
               
               
                   
                   
                 SEELASWEPLVCHTGPGAEGHSRSTQPMHLSGEASTARTCPQEPLRGTP 
               
               
                   
                   
                 GGALWLGVLRLLLFKLLLFDLLLTCSCLCDPAGPLPSPATTTRLRALGS 
               
               
                   
                   
                 HRLHPATETGGREATSSPRPQPRDRRWGDTPPGRKPGSPVWGEGSYLS 
               
               
                   
                   
                 SYPTCPAQAWCSRSALRAPSSSLGAFFAGDLPPPLQAGA 
               
               
                   
               
               
                 9 
                 human TCR  
                 PNIQNPDPAVYQLRDSKSSDKSVCLFTDFDSQTNVSQSKDSDVYITDKT 
               
               
                   
                 α-chain  
                 VLDMRSMDFKSNSAVAWSNKSDFACANAFNNSIIPEDTFFPSPESSCDV 
               
               
                   
                 C region 
                 KLVEKSFETDTNLNFQNLSVIGFRILLLKVAGFNLLMTLRLWSS 
               
               
                   
               
               
                 10 
                 human TCR  
                 MAMLLGASVLILWLQPDWVNSQQKNDDQQVKQNSPSLSVQEGRISIL 
               
               
                   
                 α-chain  
                 NCDYTNSMFDYFLWYKKYPAEGPTFLISISSIKDKNEDGRFTVFLNKSA 
               
               
                   
                 V region 
                 KHLSLHIVPSQPGDSAVYFCAAKGAGTASKLTFGTGTRLQVTL 
               
               
                   
                 CTL-L17 
                   
               
               
                   
               
               
                 11 
                 human TCR  
                 EDLNKVFPPEVAVFEPSEAEISHTQKATLVCLATGFFPDHVELSWWVN 
               
               
                   
                 β-chain C  
                 GKEVHSGVSTDPQPLKEQPALNDSRYCLSSRLRVSATFWQNPRNHFRC 
               
               
                   
                 region 
                 QVQFYGLSENDEWTQDRAKPVTQIVSAEAWGRADCGFTSVSYQQGVL 
               
               
                   
                   
                 SATILYEILLGKATLYAVLVSALVLMAMVKRKDF 
               
               
                   
               
               
                 12 
                 human TCR  
                 MGTSLLCWMALCLLGADHADTGVSQNPRHNITKRGQNVTFRCDPISE 
               
               
                   
                 β-chain V  
                 HNRLYWYRQTLGQGPEFLTYFQNEAQLEKSRLLSDRFSAERPKGSFST 
               
               
                   
                 region 
                 LEIQRTEQGDSAMYLCASSLAGLNQPQHFGDGTRLSIL 
               
               
                   
                 CTL-L17 
                   
               
               
                   
               
               
                 13 
                 human TCR  
                 MDSWTFCCVSLCILVAKHTDAGVIQSPRHEVTEMGQEVTLRCKPISGH 
               
               
                   
                 β-chain V  
                 NSLFWYRQTMMRGLELLIYFNNNVPIDDSGMPEDRFSAKMPNASFSTL 
               
               
                   
                 region YT35 
                 KIQPSEPRDSAVYFCASSFSTCSANYGYTFGSGTRLTVV 
               
               
                   
               
               
                 14 
                 PD-1 amino 
                 MQIPQAPWPVVWAVLQLGWRPGWFLDSPDRPWNPPTFSPALLVVTEG 
               
               
                   
                 acid sequence 
                 DNATFTCSFSNTSESFVLNWYRMSPSNQTDKLAAFPEDRSQPGQDCRF 
               
               
                   
                 UniProt 
                 RVTQLPNGRDFHMSVVRARRNDSGTYLCGAISLAPKAQIKESLRAELR 
               
               
                   
                 Accession No. 
                 VTERRAEVPTAHPSPSPRPAGQFQTLVVGVVGGLLGSLVLLVWVLAVI 
               
               
                   
                 Q02242 
                 CSRAARGTIGARRTGQPLKEDPSAVPVFSVDYGELDFQWREKTPEPPV 
               
               
                   
                   
                 PCVPEQTEYATIVFPSGMGTSSPARRGSADGPRSAQPLRPEDGHCSWPL 
               
               
                   
               
               
                 15 
                 PD-L1 amino 
                 MRIFAVFIFMTYWHLLNAFTVTVPKDLYVVEYGSNMTIECKFPVEKQL 
               
               
                   
                 acid sequence 
                 DLAALIVYWEMEDKNIIQFVHGEEDLKVQHSSYRQRARLLKDQLSLGN 
               
               
                   
                 UniProt 
                 AALQITDVKLQDAGVYRCMISYGGADYKRITVKVNAPYNKINQRILVV 
               
               
                   
                 Accession No. 
                 DPVTSEHELTCQAEGYPKAEVIWTSSDHQVLSGKTTTTNSKREEKLFN 
               
               
                   
                 Q9NZQ7 
                 VTSTLRINTTTNEIFYCTFRRLDPEENHTAELVIPELPLAHPPNERTHLVI 
               
               
                   
                   
                 LGAILLCLGVALTFIFRLRKGRMMDVKKCGIQDTNSKKQSDTHLEET 
               
               
                   
               
               
                 16 
                 PD-L2 amino 
                 MIFLLLMLSLELQLHQIAALFTVTVPKELYIIEHGSNVTLECNFDTGSHV 
               
               
                   
                 acid sequence 
                 NLGAITASLQKVENDTSPHRERATLLEEQLPLGKASFHIPQVQVRDEGQ 
               
               
                   
                 UniProt 
                 YQCIIIYGVAWDYKYLTLKVKASYRKINTHILKVPETDEVELTCQATGY 
               
               
                   
                 Accession No. 
                 PLAEVSWPNVSVPANTSHSRTPEGLYQVTSVLRLKPPPGRNFSCVFWN 
               
               
                   
                 Q9BQ51 
                 THVRELTLASIDLQSQMEPRTHPTWLLHIFIPFCIIAFIFIATVIALRKQLC 
               
               
                   
                   
                 QKLYSSKDTTKRPVTTTKREVNSAI 
               
               
                   
               
               
                 17 
                 PD1CD28 
                 ATGCAGATCCCACAGGCGCCCTGGCCAGTCGTCTGGGCGGTGCTAC 
               
               
                   
                 fusion 
                 AACTGGGCTGGCGGCCAGGATGGTTCTTAGACTCCCCAGACAGGCC 
               
               
                   
                 protein/ 
                 CTGGAACCCCCCCACCTTCTCCCCAGCCCTGCTCGTGGTGACCGAAG 
               
               
                   
                 switch- 
                 GGGACAACGCCACCTTCACCTGCAGCTTCTCCAACACATCGGAGAG 
               
               
                   
                 receptor,  
                 CTTCGTGCTAAACTGGTACCGCATGAGCCCCAGCAACCAGACGGAC 
               
               
                   
                 DNA sequence 
                 AAGCTGGCCGCCTTCCCCGAGGACCGCAGCCAGCCCGGCCAGGACT 
               
               
                   
                   
                 GCCGCTTCCGTGTCACACAACTGCCCAACGGGCGTGACTTCCACAT 
               
               
                   
                   
                 GAGCGTGGTCAGGGCCCGGCGCAATGACAGCGGCACCTACCTCTGT 
               
               
                   
                   
                 GGGGCCATCTCCCTGGCCCCCAAGGCGCAGATCAAAGAGAGCCTGC 
               
               
                   
                   
                 GGGCAGAGCTCAGGGTGACAGAGAGAAGGGCAGAAGTGCCCACAG 
               
               
                   
                   
                 CCCACCCCAGCCCCTCACCCAGGCCAGCCGGCCAGTTCCAAACCCT 
               
               
                   
                   
                 GGTGGTTGGTGTCGTGGGCGGCCTGCTGGGCAGCCTGGTGCTGCTA 
               
               
                   
                   
                 GTCTGGGTCCTGGCCGTCATCAGGAGTAAGAGGAGCAGGCTCCTGC 
               
               
                   
                   
                 ACAGTGACTACATGAACATGACTCCCCGCCGCCCCGGGCCCACCCG 
               
               
                   
                   
                 CAAGCATTACCAGCCCTATGCCCCACCACGCGACTTCGCAGCCTAT 
               
               
                   
                   
                 CGCTCCTGA 
               
               
                   
               
               
                 18 
                 PD1CD28 
                 MQIPQAPWPVVWAVLQLGWRPGWFLDSPDRPWNPPTFSPALLVVTEG 
               
               
                   
                 fusion 
                 DNATFTCSFSNTSESFVLNWYRMSPSNQTDKLAAFPEDRSQPGQDCRF 
               
               
                   
                 protein/ 
                 RVTQLPNGRDFHMSVVRARRNDSGTYLCGAISLAPKAQIKESLRAELR 
               
               
                   
                 switch- 
                 VTERRAEVPTAHPSPSPRPAGQFQTLVVGVVGGLLGSLVLLVWVLAVI 
               
               
                   
                 receptor,  
                 RSKRSRLLHSDYMNMTPRRPGPTRKHYQPYAPPRDFAAYRS 
               
               
                   
                 amino acid  
                   
               
               
                   
                 sequence