Patent Publication Number: US-2022218745-A1

Title: Multivalent chimeric antigen receptor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national phase application of International Patent Application No. PCT/US2018/067243, filed Dec. 21, 2018, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/609,847, filed Dec. 22, 2017, where these applications are herein incorporated by reference in their entireties. 
    
    
     STATEMENT REGARDING SEQUENCE LISTING 
     The Sequence Listing associated with this application is provided in text format in lieu of a paper copy and is hereby incorporated by reference into the specification. The name of the text file containing the Sequence Listing is BLBD_096_01WO_ST25.txt. The text file is 99 KB, was created on Dec. 21, 2018, and is being submitted electronically via EFS-Web, concurrent with the filing of the specification. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to cellular immunotherapy compositions and related methods. More particularly, the invention relates to multivalent chimeric antigen receptors, compositions, genetically modified cells, and methods of making and using the same to treat immune system disorders. 
     Description of the Related Art 
     Cancer is a significant health problem throughout the world. Based on rates from the International Agency for Research on Cancer (IARC), in 2012 there were 14.1 million new cancer cases and 8.2 million cancer deaths worldwide. In 2015, cancer was the second leading cause of death globally, and was responsible for 8.8 million deaths; nearly 1 in 6 deaths were due to cancer. By 2030, the global burden is expected to grow to 21.7 million new cancer cases and 13 million cancer deaths simply due to the growth and aging of the population. The future burden will probably be even larger because of the adoption of western lifestyles, such as smoking, poor diet, physical inactivity, and fewer childbirths, in economically developing countries. The total annual economic cost of cancer in 2010 was estimated at approximately US$ 1.16 trillion. The economic impact of cancer is significant and is increasing. 
     Although advances have been made in detection, prevention, and treatment of cancer, a universally successful therapeutic strategy has yet to be realized. The response of various forms of cancer treatment is mixed. Traditional methods of treating cancers, including chemotherapy and radiotherapy, have limited utility due to toxic side effects. Immunotherapy with therapeutic antibodies have also provided limited success, due in part to poor pharmacokinetic profiles, rapid elimination of antibodies by serum proteases and filtration at the glomerulus, and limited penetration into the tumor site and expression levels of the target antigen on tumor cells. Attempts to use genetically modified cells expressing chimeric antigen receptors (CARs) have also met with limited success due to poor in vivo expansion of CAR T cells, rapid disappearance of the cells after infusion, disappointing clinical activity, and antigen escape. 
     BRIEF SUMMARY 
     The invention generally provides improved vectors for generating T cell therapies and methods of using the same. More particularly, the invention provides multivalent CARs, CAR T cells, compositions and methods of making and using the same to treat, prevent, or ameliorate immune system disorders. 
     In various embodiments, a chimeric antigen receptor (CAR) is contemplated comprising: a single chain Fv antibody (scFv) that binds a first antigen; a single domain antibody (sdAb) or antigen binding fragment thereof that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, the CAR comprises from 5′ to 3′: a single chain Fv antibody (scFv) that binds a first antigen; a single domain antibody (sdAb) or antigen binding fragment thereof that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In some embodiments, the CAR comprises from 5′ to 3′: a single domain antibody (sdAb) or antigen binding fragment thereof that binds a second antigen; a single chain Fv antibody (scFv) that binds a first antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In some embodiments, the CAR comprises from 5′ to 3′: a single domain antibody (sdAb) or antigen binding fragment thereof that binds a first antigen; a single domain antibody (sdAb) or antigen binding fragment thereof that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, the scFv is murine, humanized, or human. 
     In some embodiments, the sdAb is a camelid VHH. 
     In certain embodiments, the first antigen is selected from the group consisting of: alpha folate receptor (FRα), α v β 6  integrin, B cell maturation antigen (BCMA), B7-H3 (CD276), B7-H6, carbonic anhydrase IX (CAIX), CD16, CD19, CD20, CD22, CD30, CD33, CD37, CD38, CD44, CD44v6, CD44v7/8, CD70, CD79a, CD79b, CD123, CD133, CD138, CD171, carcinoembryonic antigen (CEA), C-type lectin-like molecule-1 (CLL-1), CD2 subset 1 (CS-1), chondroitin sulfate proteoglycan 4 (CSPG4), cutaneous T cell lymphoma-associated antigen 1 (CTAGE1), epidermal growth factor receptor (EGFR), epidermal growth factor receptor variant III (EGFRvIII), epithelial glycoprotein 2 (EGP2), epithelial glycoprotein 40 (EGP40), epithelial cell adhesion molecule (EPCAM), ephrin type-A receptor 2 (EPHA2), fibroblast activation protein (FAP), Fc Receptor Like 5 (FCRL5), fetal acetylcholinesterase receptor (AchR), ganglioside G2 (GD2), ganglioside G3 (GD3), Glypican-3 (GPC3), EGFR family including ErbB2 (HER2), IL-10Rα, IL-13Rα2, Kappa, cancer/testis antigen 2 (LAGE-1A), Lambda, Lewis-Y (LeY), L1 cell adhesion molecule (L1-CAM), melanoma antigen gene (MAGE)-A1, MAGE-A3, MAGE-A4, MAGE-A6, MAGEA10, melanoma antigen recognized by T cells 1 (MelanA or MART1), Mesothelin (MSLN), MUC1, MUC16, neural cell adhesion molecule (NCAM), cancer/testis antigen 1 (NY-ESO-1), polysialic acid; placenta-specific 1 (PLAC1), preferentially expressed antigen in melanoma (PRAME), prostate stem cell antigen (PSCA), prostate-specific membrane antigen (PSMA), receptor tyrosine kinase-like orphan receptor 1 (ROR1), synovial sarcoma, X breakpoint 2 (SSX2), Survivin, tumor associated glycoprotein 72 (TAG72), tumor endothelial marker 1 (TEM1/CD248), tumor endothelial marker 7-related (TEM7R), trophoblast glycoprotein (TPBG), vascular endothelial growth factor receptor 2 (VEGFR2), and Wilms tumor 1 (WT-1). 
     In various embodiments, the second antigen is selected from the group consisting of: FRα, α v β 6  integrin, BCMA, B7-H3 (CD276), B7-H6, CAIX, CD16, CD19, CD20, CD22, CD30, CD33, CD37, CD38, CD44, CD44v6, CD44v7/8, CD70, CD79a, CD79b, CD123, CD133, CD138, CD171, CEA, CLL-1, CS-1, CSPG4, CTAGE1, EGFR, EGFRvIII, EGP2, EGP40, EPCAM, EPHA2, FAP, FCRL5, AchR, GD2, GD3, GPC3, HER2, IL-10Rα, IL-13Rα2, Kappa, LAGE-1A, Lambda, LeY, L1-CAM, MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A6, MAGEA10, MelanA or MART 1, MSLN, MUC1, MUC16, NCAM, NY-ESO-1, PLAC1, PRAME, PSCA, PSMA, ROR1, SSX2, Survivin, TAG72, TEM1/CD248, TM7R, TPBG, VEGFR2, and WT-1. 
     In particular embodiments, the first antigen is selected from the group consisting of: BCMA, CD19, CD20, CD22, CD23, CD33, CD37, CD38, CD52, CD80, CD123, and HLA-DR. 
     In further embodiments, the second antigen is selected from the group consisting of: BCMA, CD19, CD20, CD22, CD23, CD33, CD37, CD38, CD52, CD80, C123, and HLA-DR. 
     In various embodiments, the first antigen or second antigen is BCMA. 
     In some embodiments, the first antigen or second antigen is CD19. 
     In certain embodiments, the first antigen or second antigen is CD20. 
     In some embodiments, the first antigen or second antigen is CD22. 
     In various embodiments, the first antigen or second antigen is CD23. 
     In additional embodiments, the first antigen or second antigen is CD33. 
     In particular embodiments, the first antigen or second antigen is CD37. 
     In certain embodiments, the first antigen or second antigen is CD38. 
     In various embodiments, the first antigen or second antigen is CD52. 
     In further embodiments, the first antigen or second antigen is CD80. 
     In particular embodiments, the first antigen or second antigen is CD123. 
     In some embodiments, the first antigen or second antigen is HLA-DR. 
     In various embodiments, the first and second antigens are expressed on a cancer cell. 
     In certain embodiments, the first or second antigens are expressed on the same cancer cell. 
     In additional embodiments, the cancer is a solid cancer. 
     In various embodiments, the cancer is a liquid cancer. 
     In further embodiments, the first and second antigens are expressed on a malignant B cell. 
     In particular embodiments, the first and second antigens are expressed on a malignant plasma cell. 
     In some embodiments, the transmembrane domain is isolated from a polypeptide selected from the group consisting of: alpha or beta chain of the T-cell receptor, CDδ, CD3ε, CDγ, CDζ, CD4, CD5, CD8α, CD9, CD 16, CD22, CD27, CD28, CD33, CD37, CD45, CD64, CD71, CD80, CD86, CD 134, CD137, CD152, CD154, AMN, and PD1. 
     In various embodiments, the transmembrane domain is isolated from a polypeptide selected from the group consisting of: CD8α; CD4, CD45, PD1, and CD152. 
     In certain embodiments, the transmembrane domain is isolated from CD8α. 
     In various embodiments, the one or more costimulatory signaling domains and/or primary signaling domains comprise an immunoreceptor tyrosine activation motif (ITAM). 
     In some embodiments, the one or more costimulatory signaling domains are isolated from a costimulatory molecule selected from the group consisting of: TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, CARD11, CD2, CD7, CD27, CD28, CD30, CD40, CD54 (ICAM), CD83, CD134 (OX40), CD137 (4-1BB), CD278 (ICOS), DAP10, LAT, NKD2C, SLP76, TRIM, and ZAP70. 
     In particular embodiments, the one or more costimulatory signaling domains are isolated from a costimulatory molecule selected from the group consisting of: CD28, CD134, CD137, and CD278. 
     In further embodiments, the one or more costimulatory signaling domains is isolated from CD137. 
     In various embodiments, the primary signaling domain isolated from a polypeptide selected from the group consisting of: FcRγ, FcRβ, CD3γ, CD3δ, CD3ε, CD3ζ, CD22, CD79a, CD79b, and CD66d. 
     In particular embodiments, the primary signaling domain isolated from a CD3ζ. 
     In certain embodiments, the CAR further comprises a hinge region polypeptide. 
     In various embodiments, the hinge region polypeptide comprises a hinge region of CD8α. 
     In additional embodiments, the CAR further comprises a spacer region. 
     In some embodiments, the CAR further comprises a signal peptide. 
     In certain embodiments, the signal peptide comprises an IgG1 heavy chain signal polypeptide, a CD8α signal polypeptide, or a human GM-CSF receptor alpha signal polypeptide. 
     In various embodiments, a polynucleotide encoding a CAR contemplated herein is provided. 
     In particular embodiments, a cDNA encoding a CAR contemplated herein is provided. 
     In particular embodiments, an mRNA encoding a CAR contemplated herein is provided. 
     In various embodiments, a vector encoding a polynucleotide contemplated herein is provided. 
     In certain embodiments, the vector is an expression vector. 
     In further embodiments, the vector is an episomal vector. 
     In additional the vector is a viral vector. 
     In some embodiments, the vector is a retroviral vector. 
     In various embodiments, the vector is a lentiviral vector. 
     In further embodiments, the lentiviral vector is selected from the group consisting essentially of: human immunodeficiency virus 1 (HIV-1); human immunodeficiency virus 2 (HIV-2), visna-maedi virus (VMV) virus; caprine arthritis-encephalitis virus (CAEV); equine infectious anemia virus (EIAV); feline immunodeficiency virus (FIV); bovine immune deficiency virus (BIV); and simian immunodeficiency virus (SIV). 
     In certain embodiments, the vector comprises a left (5′) retroviral LTR, a Psi (Ψ) packaging signal, a central polypurine tract/DNA flap (cPPT/FLAP), a retroviral export element; a promoter operably linked to the polynucleotide contemplated; and a right (3′) retroviral LTR. 
     In various embodiments, the promoter of the 5′ LTR is replaced with a heterologous promoter. 
     In particular embodiments, the heterologous promoter is a cytomegalovirus (CMV) promoter, a Rous Sarcoma Virus (RSV)promoter, or a Simian Virus 40 (SV40) promoter. 
     In some embodiments, the 3′ LTR is a self-inactivating (SIN) LTR. 
     In particular embodiments, a cell comprising a CAR, a polynucleotide, and/or a vector contemplated herein is provided. 
     In particular embodiments, the cell is a hematopoietic cell. 
     In certain embodiments, the cell is an immune effector cell. 
     In further embodiments, the cell is a T cell. 
     In certain embodiments, the cell expresses CD3 + , CD4 + , CD8 + , or a combination thereof. 
     In various embodiments, the cell is a cytotoxic T lymphocyte (CTL), a tumor infiltrating lymphocyte (TIL), or a helper T cell. 
     In certain embodiments, the cell is a natural killer (NK) cell or natural killer T (NKT) cell. 
     In some embodiments, the source of the cell is peripheral blood mononuclear cells, bone marrow, lymph nodes tissue, cord blood, thymus issue, tissue from a site of infection, ascites, pleural effusion, spleen tissue, or tumors. 
     In various embodiments, a composition comprising a CAR, a polynucleotide, a vector, and/or a cell contemplated herein is provided. 
     In particular embodiments, a composition comprising a physiologically acceptable carrier and a CAR, a polynucleotide, a vector, and/or a cell contemplated herein is provided. 
     In particular embodiments, a method for making a CAR T cell comprising: introducing into a cell a CAR, a polynucleotide, a vector, and/or a cell contemplated herein is provided. 
     In some embodiments, a method of treating a cancer in a subject in need thereof, comprising administering an effective amount of a composition contemplated herein is provided. 
     In some embodiments, the cancer is a solid cancer. 
     In various embodiments, the cancer is selected from the group consisting of: adrenal cancer, adrenocortical carcinoma, anal cancer, appendix cancer, astrocytoma, atypical teratoid/rhabdoid tumor, basal cell carcinoma, bile duct cancer, bladder cancer, bone cancer, brain/CNS cancer, breast cancer, bronchial tumors, cardiac tumors, cervical cancer, cholangiocarcinoma, chondrosarcoma, chordoma, colon cancer, colorectal cancer, craniopharyngioma, ductal carcinoma in situ (DCIS) endometrial cancer, ependymoma, esophageal cancer, esthesioneuroblastoma, Ewing&#39;s sarcoma, extracranial germ cell tumor, extragonadal germ cell tumor, eye cancer, fallopian tube cancer, fibrous histiosarcoma, fibrosarcoma, gallbladder cancer, gastric cancer, gastrointestinal carcinoid tumors, gastrointestinal stromal tumor (GIST), germ cell tumors, glioma, glioblastoma, head and neck cancer, hemangioblastoma, hepatocellular cancer, hypopharyngeal cancer, intraocular melanoma, kaposi sarcoma, kidney cancer, laryngeal cancer, leiomyosarcoma, lip cancer, liposarcoma, liver cancer, lung cancer, non-small cell lung cancer, lung carcinoid tumor, malignant mesothelioma, medullary carcinoma, medulloblastoma, menangioma, melanoma, Merkel cell carcinoma, midline tract carcinoma, mouth cancer, myxosarcoma, myelodysplastic syndrome, myeloproliferative neoplasms, nasal cavity and paranasal sinus cancer, nasopharyngeal cancer, neuroblastoma, oligodendroglioma, oral cancer, oral cavity cancer, oropharyngeal cancer, osteosarcoma, ovarian cancer, pancreatic cancer, pancreatic islet cell tumors, papillary carcinoma, paraganglioma, parathyroid cancer, penile cancer, pharyngeal cancer, pheochromocytoma, pinealoma, pituitary tumor, pleuropulmonary blastoma, primary peritoneal cancer, prostate cancer, rectal cancer, retinoblastoma, renal cell carcinoma, renal pelvis and ureter cancer, rhabdomyosarcoma, salivary gland cancer, sebaceous gland carcinoma, skin cancer, soft tissue sarcoma, squamous cell carcinoma, small cell lung cancer, small intestine cancer, stomach cancer, sweat gland carcinoma, synovioma, testicular cancer, throat cancer, thymus cancer, thyroid cancer, urethral cancer, uterine cancer, uterine sarcoma, vaginal cancer, vascular cancer, vulvar cancer, and Wilms Tumor. 
     In various embodiments, the cancer is selected from the group consisting of: liver cancer, pancreatic cancer, lung cancer, breast cancer, bladder cancer, brain cancer, bone cancer, thyroid cancer, kidney cancer, and skin cancer. 
     In certain embodiments, the cancer is a liquid cancer or hematological cancer. 
     In further embodiments, the hematological malignancy is a B cell malignancy. 
     In particular embodiments, the B cell malignancy is selected from the group consisting of: leukemias, lymphomas, and multiple myelomas. 
     In certain embodiments, the B cell malignancy is selected from the group consisting of: acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), myeloblastic, promyelocytic, myelomonocytic, monocytic, erythroleukemia, hairy cell leukemia (HCL), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CIVIL), chronic myelomonocytic leukemia (CMML) and polycythemia vera, Hodgkin lymphoma, nodular lymphocyte-predominant Hodgkin lymphoma, Burkitt lymphoma, small lymphocytic lymphoma (SLL), diffuse large B-cell lymphoma, follicular lymphoma, immunoblastic large cell lymphoma, precursor B-lymphoblastic lymphoma, mantle cell lymphoma, marginal zone lymphoma, mycosis fungoides, anaplastic large cell lymphoma, Sézary syndrome, precursor T-lymphoblastic lymphoma, multiple myeloma, overt multiple myeloma, smoldering multiple myeloma, plasma cell leukemia, non-secretory myeloma, IgD myeloma, osteosclerotic myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma. 
     In some embodiments, the B cell malignancy is multiple myeloma. 
     In various embodiments, a method for ameliorating at one or more symptoms associated with a cancer in a subject, comprising administering an effective amount of a composition contemplated herein is provided. 
     In particular embodiments, the one or more symptoms ameliorated are selected from the group consisting of: weakness, fatigue, shortness of breath, easy bruising and bleeding, frequent infections, enlarged lymph nodes, distended or painful abdomen, bone or joint pain, fractures, unplanned weight loss, poor appetite, night sweats, persistent mild fever, and decreased urination. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows a cartoon of a typical antibody (left panel) and a V H H antibody (right panel) and the associated binding domains. 
         FIG. 2  shows a cartoon of a multivalent V H H-scFv CAR. 
         FIG. 3  shows a cartoon of CARchitectures for a V H H CAR, an scFv CAR, and a V H H-scFv CAR. 
         FIG. 4  shows the CAR expression of donor PBMCs transduced with an anti-EGFR V H H CAR, an anti-BCMA scFv CAR, and a multivalent anti-EGFR V H H-anti-BCMA scFv CAR. 
         FIG. 5  shows the cytoxicity of A549 cells (EGFR+BCMA+) co-cultured at an E:T ratio of 1:1 for 48 hours with donor PBMCs transduced with an anti-EGFR V H H CAR, an anti-BCMA scFv CAR, and a multivalent anti-EGFR V H H-anti-BCMA scFv CAR. 
         FIG. 6  shows IFNγ secretion from donor PBMCs transduced with an anti-EGFR V H H CAR, an anti-BCMA scFv CAR, and a multivalent anti-EGFR V H H-anti-BCMA scFv CAR and co-cultured at an E:T ratio of 1:1 for 24 hours with A549 cells (EGFR+BCMA+). 
         FIG. 7A  shows the percentage of CAR positive cells (left axis) binding either fluorescently labeled CD19 antigen or detected with a fluorescent anti-VHH antibody. Overall expression was quantified by MFI (right axis). 
         FIG. 7B  shows antigen specific cytotoxicity of CART cells co-cultured with antigen positive A549 cells. 
         FIG. 7C  shows IFNγ secretion of transduced human T cells expressing CAR constructs at 24 h post co-culture. 
         FIG. 7D  shows IL-2 secretion of transduced human T cells expressing CAR constructs at 24 h post co-culture. 
         FIG. 8A  shows the percentage of CAR positive cells binding either fluorescently labeled CD19 antigen, fluorescently labeled CD79a antigen or detected with a fluorescent anti-VHH antibody. 
         FIG. 8B  shows antigen specific cytotoxicity of CART cells co-cultured with antigen positive A549 cells. Cytotoxicity is inversely proportional to AUC. Low AUC indicates higher levels of tumor cell killing. 
         FIG. 8C  shows INFγ secretion of transduced human T cells expressing CAR constructs at 24 h post tumor cell co-culture. Tandem constructs display antigen specific responses in line with CAR specificity. Daudi cells are positive for CD19, CD20 and CD79a antigens. 
         FIG. 8D  shows TNFα secretion of transduced human T cells expressing CAR constructs at 24 h post tumor cell co-culture. Tandem constructs display antigen specific responses in line with CAR specificity. Daudi cells are positive for CD19, CD20 and CD79a antigens. 
     
    
    
     BRIEF DESCRIPTION OF THE SEQUENCE IDENTIFIERS 
     SEQ ID NO: 1 sets forth the polynucleotide sequence of an anti-EFGR V H H domain. 
     SEQ ID NO: 2 sets forth the polypeptide sequence of an anti-EFGR V H H domain. 
     SEQ ID NO: 3 sets forth the polynucleotide sequence of an anti-EFGR V H H CAR. 
     SEQ ID NO: 4 sets forth the polypeptide sequence of an anti-EFGR V H H CAR. 
     SEQ ID NO: 5 sets forth the polynucleotide sequence of an anti-BCMA scFv CAR. 
     SEQ ID NO: 6 sets forth the polypeptide sequence of an anti-BCMA scFv CAR. 
     SEQ ID NO: 7 sets forth the polynucleotide sequence of a multivalent anti-EGFR V H H-anti-BCMA scFv CAR. 
     SEQ ID NO: 8 sets forth the polypeptide sequence of a multivalent anti-EGFR V H H-anti-BCMA scFv CAR. 
     SEQ ID NO: 9 sets forth the polynucleotide sequence of an anti-CD20 scFv. 
     SEQ ID NO: 10 sets forth the polypeptide sequence of an anti-CD20 scFv. 
     SEQ ID NO: 11 sets forth the polynucleotide sequence of an anti-CD20 scFv CAR. 
     SEQ ID NO: 12 sets forth the polypeptide sequence of an anti-CD20 scFv CAR. 
     SEQ ID NO: 13 sets forth the polynucleotide sequence of an anti-CD19 scFv. 
     SEQ ID NO: 14 sets forth the polypeptide sequence of an anti-CD19 scFv. 
     SEQ ID NO: 15 sets forth the polynucleotide sequence of an anti-CD19 scFv CAR. 
     SEQ ID NO: 16 sets forth the polypeptide sequence of an anti-CD19 scFv CAR. 
     SEQ ID NO: 17 sets forth the polynucleotide sequence of an anti-CD19 V H H domain. 
     SEQ ID NO: 18 sets forth the polypeptide sequence of an anti-CD19 V H H domain. 
     SEQ ID NO: 19 sets forth the polynucleotide sequence of an anti-CD20 V H H domain. 
     SEQ ID NO: 20 sets forth the polypeptide sequence of an anti-CD20 V H H domain. 
     SEQ ID NO: 21 sets forth the polynucleotide sequence of a tandem anti-CD19 V H H-anti-CD20 scFv CAR. 
     SEQ ID NO: 22 sets forth the polypeptide sequence of a tandem anti-CD19 V H H-anti-CD20 scFv CAR. 
     SEQ ID NO: 23 sets forth the polynucleotide sequence of a tandem anti-CD20 V H H-anti-CD19 scFv CAR. 
     SEQ ID NO: 24 sets forth the polypeptide sequence of a tandem anti-CD20 V H H-anti-CD19 scFv CAR. 
     SEQ ID NO: 25 sets forth the polynucleotide sequence of a tandem anti-CD19 V H H-anti-CD20 V H H CAR. 
     SEQ ID NO: 26 sets forth the polypeptide sequence of a tandem anti-CD19 V H H-anti-CD20 V H H CAR. 
     SEQ ID NO: 27 sets forth the polynucleotide sequence of an anti-CD79a scFv. 
     SEQ ID NO: 28 sets forth the polypeptide sequence of an anti-CD79a scFv. 
     SEQ ID NO: 29 sets forth the polynucleotide sequence of a tandem anti-CD20 V H H-anti-CD79a scFv CAR. 
     SEQ ID NO: 30 sets forth the polypeptide sequence of a tandem anti-CD20 V H H-anti-CD79a scFv CAR. 
     SEQ ID NO: 31 sets forth the polynucleotide sequence of an anti-CD79a scFv CAR. 
     SEQ ID NO: 32 sets forth the polypeptide sequence of an anti-CD79a scFv CAR. 
     SEQ ID NO: 33 sets forth the polynucleotide sequence of a tandem anti-CD20 V H H CAR. 
     SEQ ID NO: 34 sets forth the polypeptide sequence of a tandem anti-CD20 V H H CAR. 
     SEQ ID NOs: 35-46 set forth the amino acid sequences of various linkers. 
     SEQ ID NOs: 47-71 set forth the amino acid sequences of protease cleavage sites and self-cleaving polypeptide cleavage sites. 
     In the foregoing sequences, X, if present, refers to any amino acid or the absence of an amino acid. 
     DETAILED DESCRIPTION 
     A. Overview 
     Cancers are often heterogeneous pools of cells expressing different levels of various antigens. Generally, immunotherapies are initially selected to target an antigen that is expressed on a majority of cancer cells and that substantially lacks expression on normal cells. An effective targeted immunotherapy will kill the majority of cancer cells that express the target antigen, resulting in partial or complete remission. However, because most cancers are heterogeneous in nature, the remaining cancer cells that do not express, or that express low levels, of the targeted antigen are spared and can potentially give rise to cancer cells that are not effectively targeted by the initial immunotherapy. 
     One major obstacle that still limits the efficacy of CART cell therapy is relapse of “antigen negative” cancers. For example, although anti-CD19 CAR T cell therapy initially results in impressive remission rates in relapsed and refractory acute ALL, relapse of CD19 negative leukemic blasts occurs in approximately 10-20% of cases. The alarmingly high rate of antigen negative relapse represents an, as of yet, unaddressed weakness of CAR T immunotherapy. Without wishing to be bound by any particular theory, the inventors have solved the problem by re-engineering CARs so that they may retarget a virtually unlimited number of additional antigens expressed on the relapsed or refractory antigen negative cancer cells. Thus, the compositions and methods contemplated herein represent an important advance in CAR T cell immunotherapy. 
     In various embodiments, a multivalent chimeric antigen receptor (CAR) that targets a plurality of target antigens is provided. The CAR may comprise two or more antigen binding domains, a transmembrane domain, and one or more intracellular signaling domains. CARs contemplated in particular embodiments comprise one or more single domain antibody (sdAb) binding domains directed to one, two, three or more target antigens. CARs contemplated in certain embodiments comprise one or more single domain antibody binding domains and a single chain variable fragment (scFv) binding domain directed to two, three, four or more target antigens. 
     In various embodiments, a CAR comprises two or more sdAb antigen binding domains. 
     In various embodiments, a CAR comprises an sdAb antigen binding domain and an scFv. 
     In particular embodiments, a CAR comprises an sdAb antigen binding domain is N-terminal to an scFv, and in other particular embodiments, a CAR comprises an scFv is N-terminal to an sdAb. 
     In particular embodiments, an immune effector cell is modified to express one or more multivalent CARs contemplated herein. 
     In various embodiments, modified immune effector cells comprising one or more multivalent CARs are administered to a patient with an immune system disorder including, but not limited to, a cancer, graft-versus-host disease, an infectious disease, an autoimmune disease, or an immunodeficiency. 
     Techniques for recombinant (i.e., engineered) DNA, peptide and oligonucleotide synthesis, immunoassays, tissue culture, transformation (e.g., electroporation, lipofection), enzymatic reactions, purification and related techniques and procedures may be generally performed as described in various general and more specific references in microbiology, molecular biology, biochemistry, molecular genetics, cell biology, virology and immunology as cited and discussed throughout the present specification. See, e.g., Sambrook et al.,  Molecular Cloning: A Laboratory Manual,  3d ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.;  Current Protocols in Molecular Biology  (John Wiley and Sons, updated July 2008);  Short Protocols in Molecular Biology: A Compendium of Methods from Current Protocols in Molecular Biology , Greene Pub. Associates and Wiley-Interscience; Glover,  DNA Cloning: A Practical Approach,  vol. I &amp; II (IRL Press, Oxford Univ. Press USA, 1985);  Current Protocols in Immunology  (Edited by: John E. Coligan, Ada M. Kruisbeek, David H. Margulies, Ethan M. Shevach, Warren Strober 2001 John Wiley &amp; Sons, NY, NY);  Real - Time PCR: Current Technology and Applications , Edited by Julie Logan, Kirstin Edwards and Nick Saunders, 2009, Caister Academic Press, Norfolk, UK; Anand,  Techniques for the Analysis of Complex Genomes , (Academic Press, New York, 1992); Guthrie and Fink,  Guide to Yeast Genetics and Molecular Biology  (Academic Press, New York, 1991);  Oligonucleotide Synthesis  (N. Gait, Ed., 1984);  Nucleic Acid The Hybridization  (B. Hames &amp; S. Higgins, Eds., 1985);  Transcription and Translation  (B. Hames &amp; S. Higgins, Eds., 1984);  Animal Cell Culture  (R. Freshney, Ed., 1986); Perbal,  A Practical Guide to Molecular Cloning  (1984);  Next - Generation Genome Sequencing  (Janitz, 2008 Wiley-VCH);  PCR Protocols  ( Methods in Molecular Biology ) (Park, Ed., 3rd Edition, 2010 Humana Press);  Immobilized Cells And Enzymes  (IRL Press, 1986); the treatise,  Methods In Enzymology  (Academic Press, Inc., N.Y.);  Gene Transfer Vectors For Mammalian Cells  (J. H. Miller and M. P. Calos eds., 1987, Cold Spring Harbor Laboratory); Harlow and Lane,  Antibodies , (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1998);  Immunochemical Methods In Cell And Molecular Biology  (Mayer and Walker, eds., Academic Press, London, 1987);  Handbook Of Experimental Immunology , Volumes I-IV (D. M. Weir and C C Blackwell, eds., 1986); Roitt,  Essential Immunology,  6th Edition, (Blackwell Scientific Publications, Oxford, 1988);  Current Protocols in Immunology  (Q. E. Coligan, A. M. Kruisbeek, D. H. Margulies, E. M. Shevach and W. Strober, eds., 1991);  Annual Review of Immunology ; as well as monographs in journals such as  Advances in Immunology.    
     B. Definitions 
     Prior to setting forth this disclosure in more detail, it may be helpful to an understanding thereof to provide definitions of certain terms to be used herein. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of particular embodiments, preferred embodiments of compositions, methods and materials are described herein. For the purposes of the present disclosure, the following terms are defined below. 
     The articles “a,” “an,” and “the” are used herein to refer to one or to more than one (i.e., to at least one, or to one or more) of the grammatical object of the article. By way of example, “an element” means one element or one or more elements. 
     The use of the alternative (e.g., “or”) should be understood to mean either one, both, or any combination thereof of the alternatives. 
     The term “and/or” should be understood to mean either one, or both of the alternatives. 
     In one embodiment, a range, e.g., 1 to 5, about 1 to 5, or about 1 to about 5, refers to each numerical value encompassed by the range. For example, in one non-limiting and merely illustrative embodiment, the range “1 to 5” is equivalent to the expression 1, 2, 3, 4, 5; or 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0; or 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0. 
     As used herein, the term “substantially” refers to a quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length that is 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or higher compared to a reference quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length. In one embodiment, “substantially the same” refers to a quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length that produces an effect, e.g., a physiological effect, that is approximately the same as a reference quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length. 
     As used herein, the term “about” or “approximately” refers to a quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length that varies by as much as 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1% to a reference quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length. In one embodiment, the term “about” or “approximately” refers a range of quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length ±15%, ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%, ±2%, or ±1% about a reference quantity, level, value, number, frequency, percentage, dimension, size, amount, weight or length. 
     Throughout this specification, unless the context requires otherwise, the words “comprise,” “comprises,” and “comprising” will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements. By “consisting of” is meant including, and limited to, whatever follows the phrase “consisting of” Thus, the phrase “consisting of” indicates that the listed elements are required or mandatory, and that no other elements may be present. By “consisting essentially of” is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase “consisting essentially of” indicates that the listed elements are required or mandatory, but that no other elements are present that materially affect the activity or action of the listed elements. 
     Reference throughout this specification to “one embodiment,” “an embodiment,” “a particular embodiment,” “a related embodiment,” “a certain embodiment,” “an additional embodiment,” or “a further embodiment” or combinations thereof means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the foregoing phrases in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It is also understood that the positive recitation of a feature in one embodiment, serves as a basis for excluding the feature in a particular embodiment. 
     C. Multivalent Chimeric Antigen Receptors 
     In various embodiments, engineered receptors that redirect cytotoxicity of immune effector cells toward cancer cells expressing target antigens are provided. These engineered receptors referred to herein as multivalent chimeric antigen receptors (CARs). Multivalent CARs are molecules that combine antibody-based specificity for target antigens with a T cell receptor-activating intracellular domain to generate a chimeric protein that exhibits antigen specific cellular immune activity. Multivalent CARs comprise two or more antigen binding domains directed to two or more target antigens, which allows the CAR to redirect immune effector cell activity to target cells expressing one or more target antigens or to a heterogenous population of target cells expressing the target antigen(s). As used herein, the term, “chimeric,” describes being composed of parts of different proteins or DNAs from different origins. 
     In various embodiments, multivalent CARs contemplated herein have been engineered to redirect cytotoxicity of immune effector cells toward target cells expressing two or more target antigens. Relapsed or refractory cancers are a prevelant problem plaguing the cellular immunotherapy field. In some embodiments, the target cells are tumor cells characterized by a high incidence of relapse or refractoriness to monovalent CART cell therapies. Without wishing to be bound by any particular theory, it is contemplated that immune effector cells that express multivalent CARs will increase immunotherapy efficacy and decrease the likelihood of occurrence of relapsed or refractory cancer cells. For example, a patient treated for a cancer expressing antigen X with anti-X CAR T cells may initially show improvement and cancer regression, but eventually, the cancer may return, lacking X expression. This scenario presents a serious problem because the CAR T cells residing in the patient are specific to X and thus, the relapsed or refractory X negative cancer cells are invisible to the immune system and will grow unchecked without additional therapeutic intervention. The multivalent CARs contemplated herein provides a therapeutic solution to the antigen escape problem by simultaneously targeting multiple target antigens expressed on the cancer cells, thereby increasing CAR T cell efficacy against the cancer cells and decreasing the incidence of antigen escape. 
     In particular embodiments, a CAR comprises an extracellular domain that comprises multivalent antigen binding domains that bind to multiple target antigens, a transmembrane domain, and one or more intracellular signaling domains. Traditional monovalent CARs comprise scFv antigen binding domains to target antigens. The multivalent CARs contemplated herein take advantage of the monomeric and modular nature of single domain antibodies including, but not limited to, heavy chain only antibodies or antigen binding fragments thereof isolated from camelids (V H H antibodies) or cartilaginous fish (IgNAR antibodies). In preferred embodiments, the multivalent CARs contemplated herein comprise one or more sdAbs or antigen binding fragments or domains thereof e.g, a V H H domain, and one or more scFvs or antigen binding fragments or domains thereof. In preferred embodiments, multivalent CARs contemplated herein comprise an sdAb or antigen binding fragment thereof that binds a first antigen and an scFv or antigen binding fragments thereof that that binds a second antigen. In preferred embodiments, multivalent CARs contemplated herein comprise an scFv or antigen binding fragment thereof that binds a first antigen and an sdAb or antigen binding fragments thereof that that binds a second antigen. 
     Engagement of one or more antigen binding domains of the CAR with the one or more target antigens expressed on the surface of a target cell results in clustering of the CAR and delivers an activation stimulus to the CAR-containing cell. The main characteristic of CARs is their ability to redirect immune effector cell specificity, thereby triggering proliferation, cytokine production, phagocytosis or production of molecules that can mediate cell death of the target antigen expressing cell in a major histocompatibility (MHC) independent manner, exploiting the cell specific targeting abilities of monoclonal antibodies, soluble ligands or cell specific co-receptors. 
     In various embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a V H H domain, and an scFv; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a V H H domain, that binds a first antigen and an scFv that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. In particular embodiments, the first and second antigens are selected from the group consisting of: CD19, CD20, CD22, CD23, CD33, CD37, CD38, CD52, CD80, C123, and HLA-DR. 
     In particular embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a VHH domain, that binds a first antigen selected from the group consisting of: CD19, CD20, CD22, CD23, CD33, CD37, CD38, CD52, CD80, C123, and HLA-DR.and an scFv that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a VHH domain, that binds a first antigen and an scFv that binds a second antigen selected from the group consisting of: CD19, CD20, CD22, CD23, CD33, CD37, CD38, CD52, CD80, C123, and HLA-DR.; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a VHH domain, that binds a first antigen and an anti-BCMA or anti-CD19 scFv; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     In particular embodiments, a CAR comprises an extracellular binding domain that comprises an sdAb or antigen binding fragment thereof, e.g, a VHH domain, that binds BCMA or CD19 and an scFv that binds a second antigen; a transmembrane domain; one or more intracellular costimulatory signaling domains; and/or a primary signaling domain. 
     1. Binding Domain 
     In particular embodiments, CARs comprise an extracellular binding domain that comprises one or more sdAb or antigen binding fragments or domains thereof that specifically bind to a first antigen expressed on a target cell, and one or more scFv antibodies or antigen binding fragments or domains thereof that specifically bind to a second antigen expressed on a target cell. The first and second antigens, e.g., target antigens, can be expressed on the same cell or on different cells within a heterogenous population of cells. As used herein, the terms, “binding domain,” “extracellular domain,” “extracellular binding domain,” “antigen-specific binding domain,” and “extracellular antigen specific binding domain,” are used interchangeably and provide a CAR with the ability to specifically bind to a target antigen. Binding domains may be derived either from a natural, synthetic, semi-synthetic, or recombinant source. In preferred embodiments, multivalent CARS contemplated herein comprise two or more antigen binding domains in series (in tandem or in line), wherein each binding domain binds a different antigen. 
     The terms “specific binding affinity” or “specifically binds” or “specifically bound” or “specific binding” or “specifically targets” as used herein, describe binding of an antibody or antigen binding fragment thereof (or a CAR comprising the same) to a target antigen at greater binding affinity than background binding. A binding domain (or a CAR comprising a binding domain or a fusion protein containing a binding domain) “specifically binds” to an target antigen if it binds to or associates with the antigen with an affinity or K a  (i.e., an equilibrium association constant of a particular binding interaction with units of 1/M) of, for example, greater than or equal to about 10 5  M −1 . In certain embodiments, a binding domain (or a fusion protein thereof) binds to a target with a K a  greater than or equal to about 10 6  M −1 , 10 7  M −1 , 10 8  M −1 , 10 9  M −1 , 10 10  M −1 , 10 11  M −1 , 10 12  M −1 , or 10 13  M −1 . “High affinity” binding domains (or single chain fusion proteins thereof) refers to those binding domains with a K a  of at least 10 7  M −1 , at least 10 8  M −1 , at least 10 9  M −1 , at least 10 10  M −1 , at least 10 11  M −1 , at least 10 12  M −1 , at least 10 13  M −1 , or greater. 
     Alternatively, affinity may be defined as an equilibrium dissociation constant (K d ) of a particular binding interaction with units of M (e.g., 10 −5  M to 10 −13  M, or less). Affinities of binding domain polypeptides and CAR proteins according to the present disclosure can be readily determined using conventional techniques, e.g., by competitive ELISA (enzyme-linked immunosorbent assay), or by binding association, or displacement assays using labeled ligands, or using a surface-plasmon resonance device such as the Biacore T100, which is available from Biacore, Inc., Piscataway, N.J., or optical biosensor technology such as the EPIC system or EnSpire that are available from Corning and Perkin Elmer respectively (see also, e.g., Scatchard et al. (1949)  Ann. N.Y. Acad. Sci.  51:660; and U.S. Pat. Nos. 5,283,173; 5,468,614, or the equivalent) . 
     In particular embodiments, the extracellular binding domain of a CAR comprises two or more antibody fragments or antigen binding domains thereof that bind two or more antigens. An “antibody” refers to a binding agent that is a polypeptide comprising at least a light chain or heavy chain immunoglobulin variable region which specifically recognizes and binds an epitope of an antigen, such as a lipid, carbohydrate, polysaccharide, glycoprotein, peptide, or nucleic acid containing an antigenic determinant, such as those recognized by an immune cell. 
     An “antigen (Ag)” refers to a compound, composition, or substance that can stimulate the production of antibodies or a T cell response in an animal, including compositions (such as one that includes a cancer-specific protein) that are injected or absorbed into an animal. Exemplary antigens include but are not limited to lipids, carbohydrates, polysaccharides, glycoproteins, peptides, or nucleic acids. 
     A “target antigen” or “target antigen of interest” is an antigen that a binding domain contemplated herein, is designed to bind. In particular embodiments, the target antigen is selected from the group consisting of: FRα, α v β 6  integrin, BCMA, B7-H3 (CD276), B7-H6, CAIX, CD16, CD19, CD20, CD22, CD30, CD33, CD37, CD38, CD44, CD44v6, CD44v7/8, CD70, CD79a, CD79b, CD123, CD133, CD138, CD171, CEA, CLL-1, CS-1, CSPG4, CTAGE1, EGFR, EGFRvIII, EGP2, EGP40, EPCAM, EPHA2, FAP, FCRL5, AchR, GD2, GD3, GPC3, HER2, IL-10Rα, IL-13Rα2, Kappa, LAGE-1A, Lambda, LeY, L1-CAM, MAGE-A1, MAGE-A3, MAGE-A4, MAGE-A6, MAGEA10, MelanA or MART1, MSLN, MUC1, MUC16, NCAM, NY-ESO-1, PLAC1, PRAME, PSCA, PSMA, ROR1, SSX2, Survivin, TAG72, TEM1/CD248, TEM7R, TPBG, VEGFR2, and WT-1. 
     In one embodiment, the antigen is an MHC-peptide complex, such as a class I MHC-peptide complex or a class II WIC-peptide complex. 
     An “epitope” or “antigenic determinant” refers to the region of an antigen to which a binding agent binds. 
     Antibodies include antigen binding fragments or domains thereof, such as Camel Ig, a Llama Ig, an Alpaca Ig, Ig NAR, a Fab&#39; fragment, a F(ab′) 2  fragment, a bispecific Fab dimer (Fab2), a trispecific Fab trimer (Fab3), an Fv, an single chain Fv protein (“scFv”), a bis-scFv, (scFv) 2 , a minibody, a diabody, a triabody, a tetrabody, a disulfide stabilized Fv protein (“dsFv”), and a single-domain antibody (sdAb, a camelid VHH, Nanobody) or other antibody fragments thereof. The term also includes genetically engineered forms such as chimeric antibodies (for example, humanized murine antibodies), heteroconjugate antibodies (such as, bispecific antibodies) and antigen binding fragments thereof. See also, Pierce Catalog and Handbook, 1994-1995 (Pierce Chemical Co., Rockford, Ill.); Kuby, J., Immunology, 3rd Ed., W. H. Freeman &amp; Co., New York, 1997. 
     Light and heavy chain variable regions contain a “framework” region interrupted by three hypervariable regions, also called “complementarity-determining regions” or “CDRs.” The CDRs can be defined or identified by conventional methods, such as by sequence according to Kabat et al. (Wu, TT and Kabat, E. A.,  J Exp Med.  132(2):211-50, (1970); Borden, P. and Kabat E. A., PNAS, 84: 2440-2443 (1987); (see, Kabat et al.,  Sequences of Proteins of Immunological Interest , U.S. Department of Health and Human Services, 1991, which is hereby incorporated by reference), or by structure according to Chothia et al (Chothia, C. and Lesk, A. M.,  J Mol. Biol.,  196(4): 901-917 (1987), Chothia, C. et al,  Nature,  342: 877-883 (1989)). The CDRs of each chain are typically referred to as CDR1, CDR2, and CDR3, numbered sequentially starting from the N-terminus, and are also typically identified by the chain in which the particular CDR is located. Thus, the CDRs located in the variable domain of the heavy chain of the antibody are referred to as CDRH1, CDRH2, and CDRH3, whereas the CDRs located in the variable domain of the light chain of the antibody are referred to as CDRL1, CDRL2, and CDRL3. 
     Illustrative examples of rules for predicting light chain CDRs include: CDR-L1 starts at about residue 24, is preceded by a Cys, is about 10-17 residues, and is followed by a Trp (typically Trp-Tyr-Gln, but also, Trp-Leu-Gln, Trp-Phe-Gln, Trp-Tyr-Leu); CDR-L2 starts about 16 residues after the end of CDR-L1, is generally preceded by Ile-Tyr, but also, Val-Tyr, Ile-Lys, Ile-Phe, and is 7 residues; and CDR-L3 starts about 33 residues after the end of CDR-L2, is preceded by a Cys, is 7-11 residues, and is followed by Phe-Gly-XXX-Gly (SEQ ID NO:73) (XXX is any amino acid). 
     Illustrative examples of rules for predicting heavy chain CDRs include: CDR-H1 starts at about residue 26, is preceded by Cys-XXX-XXX-XXX (SEQ ID NO:74), is 10-12 residues and is followed by a Trp (typically Trp-Val, but also, Trp-Ile, Trp-Ala); CDR-H2 starts about 15 residues after the end of CDR-H1, is generally preceded by Leu-Glu-Trp-Ile-Gly (SEQ ID NO:75), or a number of variations, is 16-19 residues, and is followed by Lys/Arg-Leu/Ile/Val/Phe/Thr/Ala-Thr/Ser/Ile/Ala; and CDR-H3 starts about 33 residues after the end of CDR-H2, is preceded by Cys-XXX-XXX (typically Cys-Ala-Arg), is 3 to 25 residues, and is followed by Trp-Gly-XXX-Gly (SEQ ID NO:76). 
     In one embodiment, light chain CDRs and the heavy chain CDRs are determined according to the Kabat method 
     In one embodiment, light chain CDRs and the heavy chain CDR2 and CDR3 are determined according to the Kabat method, and heavy chain CDR1 is determined according to the AbM method, which is a comprise between the Kabat and Clothia methods, see e.g., Whitelegg N &amp; Rees A R,  Protein Eng.  2000 December; 13(12):819-24 and  Methods Mol Biol.  2004; 248:51-91. Programs for predicting CDRs are publicly available, e.g., AbYsis (www.bioinf. org.uk/abysis/). 
     References to “VL” or “VL” refer to the variable region of an immunoglobulin light chain, including that of an antibody, Fv, scFv, dsFv, Fab, or other antibody fragment as disclosed herein. 
     References to “VH” or “VH” refer to the variable region of an immunoglobulin heavy chain, including that of an antibody, Fv, scFv, dsFv, Fab, V H H, IgNAR, or other antibody fragment as disclosed herein. 
     In preferred embodiments, an extracellular binding domain of a multivalent CAR comprises a sdAb such as V H H or IgNAR or antigen binding fragment or domain thereof and an scFv. 
     In particular embodiments, a binding domain of a multivalent CAR is derived from a human antibody (such as a human monoclonal antibody) or fragment thereof that specifically binds to a target antigen. Human antibodies can be constructed by combining Fv clone variable domain sequence(s) selected from human-derived phage display libraries with known human constant domain sequences(s) as described above. Alternatively, human monoclonal antibodies may be made by the hybridoma method. Human myeloma and mouse-human heteromyeloma cell lines for the production of human monoclonal antibodies have been described, for example, by Kozbor  J. Immunol.,  133: 3001 (1984); Brodeur et al.,  Monoclonal Antibody Production Techniques and Applications , pp. 51-63 (Marcel Dekker, Inc., New York, 1987); and Boerner et al.,  J. Immunol.,  147: 86 (1991). In addition, transgenic animals (e.g., mice) can be used to produce a full repertoire of human antibodies in the absence of endogenous immunoglobulin production. See, e.g., Jakobovits et al.,  PNAS USA,  90: 2551 (1993); Jakobovits et al.,  Nature,  362: 255 (1993); Bruggermann et al.,  Year in Immunol.,  7: 33 (1993). Gene shuffling can also be used to derive human antibodies from non-human, e.g., rodent antibodies, where the human antibody has similar affinities and specificities to the starting non-human antibody. (see PCT WO 93/06213 published Apr. 1, 1993). Unlike traditional humanization of non-human antibodies by CDR grafting, this technique provides completely human antibodies, which have no FR or CDR residues of non-human origin. 
     In particular embodiments, a binding domain of a multivalent CAR is “humanized.” A humanized antibody is an immunoglobulin including a human framework region and one or more CDRs from a non-human (for example a camelid, shark, mouse, or rat) immunoglobulin. The non-human immunoglobulin providing the CDRs is termed a “donor,” and the human immunoglobulin providing the framework is termed an “acceptor.” In one embodiment, all the CDRs are from the donor immunoglobulin in a humanized immunoglobulin. Constant regions need not be present, but if they are, they must be substantially identical to human immunoglobulin constant regions, i.e., at least about 85-90%, such as about 95% or more identical. Humanized or other monoclonal antibodies can have additional conservative amino acid substitutions, which have substantially no effect on antigen binding or other immunoglobulin functions. Humanized antibodies can be constructed by means of genetic engineering (see for example, U.S. Pat. No. 5,585,089). 
     In particular embodiments, an extracellular binding domain of a multivalent CAR comprises a camelid V H H, preferably a humanized camelid V H H, or IgNAR or antigen binding fragment or domain thereof and an scFv. In a particular embodiment, the single domain antibody is derived from an scFv, i.e., one or two VH domains isolated from an scFv. 
     “Single domain antibody” or “sdAb” or “nanobody” refers to an antibody fragment that consists of the variable region of an antibody heavy chain (V H  domain) or the variable region of an antibody light chain (V L  domain) (Holt, L., et al, Trends in Biotechnology, 21(11): 484-490). 
     “Camel Ig” or “camelid V H H” as used herein refers to the smallest known antigen-binding unit of a heavy chain antibody (Koch-Nolte, et al,  FASEB J.,  21: 3490-3498 (2007)). A “heavy chain antibody” or a “camelid antibody” refers to an antibody that contains two V H  domains and no light chains (Riechmann L. et al,  J. Immunol. Methods  231:25-38 (1999); WO94/04678; WO94/25591; U.S. Pat. No. 6,005,079). In particular embodiments, camelid antibodies include Camel Ig, Alpaca Ig, and Llama Ig. 
     “IgNAR” of “immunoglobulin new antigen receptor” refers to class of antibodies from the shark immune repertoire that consist of homodimers of one variable new antigen receptor (VNAR) domain and five constant new antigen receptor (CNAR) domains. IgNARs represent some of the smallest known immunoglobulin-based protein scaffolds and are highly stable and possess efficient binding characteristics. The inherent stability can be attributed to both (i) the underlying Ig scaffold, which presents a considerable number of charged and hydrophilic surface exposed residues compared to the conventional antibody V H  and V L  domains found in murine antibodies; and (ii) stabilizing structural features in the complementary determining region (CDR) loops including inter-loop disulfide bridges, and patterns of intra-loop hydrogen bonds. 
     “Single-chain Fv” or “scFv” antibody fragments comprise the V H  and V L  domains of an antibody, wherein these domains are present in a single polypeptide chain and in either orientation (e.g., V L -V H  or V H -V L ). Generally, the scFv polypeptide further comprises a polypeptide linker between the V H  and V L  domains which enables the scFv to form the desired structure for antigen binding. For a review of scFv, see, e.g., Pluckthün, in  The Pharmacology of Monoclonal Antibodies , vol. 113, Rosenburg and Moore eds., (Springer-Verlag, New York, 1994), pp. 269-315. A technique which can be used for cloning the variable region heavy chain (V H ) and variable region light chain (V L ) has been described, for example, in Orlandi et al., PNAS, 1989; 86: 3833-3837. 
     Papain digestion of antibodies produces two identical antigen-binding fragments, called “Fab” fragments, each with a single antigen-binding site, and a residual “Fc” fragment, whose name reflects its ability to crystallize readily. Pepsin treatment yields an F(ab′)2 fragment that has two antigen-combining sites and is still capable of cross-linking antigen. 
     “Fv” is the minimum antibody fragment which contains a complete antigen-binding site. In one embodiment, a two-chain Fv species consists of a dimer of one heavy- and one light-chain variable domain in tight, non-covalent association. In a single-chain Fv (scFv) species, one heavy- and one light-chain variable domain can be covalently linked by a flexible peptide linker such that the light and heavy chains can associate in a “dimeric” structure analogous to that in a two-chain Fv species. It is in this configuration that the three hypervariable regions (HVRs) of each variable domain interact to define an antigen-binding site on the surface of the VH-VL dimer. Collectively, the six HVRs confer antigen-binding specificity to the antibody. However, even a single variable domain (or half of an Fv comprising only three HVRs specific for an antigen) has the ability to recognize and bind antigen, although at a lower affinity than the entire binding site. 
     The Fab fragment contains the heavy- and light-chain variable domains and also contains the constant domain of the light chain and the first constant domain (CH1) of the heavy chain. Fab′ fragments differ from Fab fragments by the addition of a few residues at the carboxy terminus of the heavy chain CH1 domain including one or more cysteines from the antibody hinge region. Fab′-SH is the designation herein for Fab′ in which the cysteine residue(s) of the constant domains bear a free thiol group. F(ab′)2 antibody fragments originally were produced as pairs of Fab′ fragments which have hinge cysteines between them. Other chemical couplings of antibody fragments are also known. 
     The term “diabodies” refers to antibody fragments with two antigen-binding sites, which fragments comprise a heavy-chain variable domain (VH) connected to a light-chain variable domain (VL) in the same polypeptide chain (VH-VL). By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites. Diabodies may be bivalent or bispecific. Diabodies are described more fully in, for example, EP 404,097; WO 1993/01161; Hudson et al.,  Nat. Med.  9:129-134 (2003); and Hollinger et al.,  PNAS USA  90: 6444-6448 (1993). Triabodies and tetrabodies are also described in Hudson et al.,  Nat. Med.  9:129-134 (2003). 
     In particular embodiments, a CAR comprises a humanized camelid V H H that binds a first antigen and a murine, humanized, or human scFv that binds a second antigen. 
     In a preferred embodiment, a CAR comprises a humanized camelid V H H that binds a first antigen and a murine scFv that binds a second antigen. 
     2. Linkers 
     In certain embodiments, multivalent CARs comprise one or more linkers. A “linker” refers to a plurality of amino acid residues between various polypeptide domains in a CAR, e.g., between antigen binding domains and between V H  and V L  regions of an antigen binding domain, added for appropriate spacing and conformation of the molecule. In particular embodiments the linker is a variable region linking sequence. A “variable region linking sequence,” is an amino acid sequence that connects the V H  and V L  domains and provides a spacer function compatible with interaction of the two sub-binding domains so that the resulting polypeptide retains a specific binding affinity to the same target molecule as an antibody that comprises the same light and heavy chain variable regions. In particular embodiments, a linker separates an sdAb or fragment thereof and an scFv, one or more heavy or light chain variable domains in an scFv, hinge domains, transmembrane domains, costimulatory domains, and/or primary signaling domains. CARs comprise one, two, three, four, or five or more linkers. In particular embodiments, the length of a linker is about 1 to about 25 amino acids, about 5 to about 20 amino acids, or about 10 to about 20 amino acids, or any intervening length of amino acids. In some embodiments, the linker is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or more amino acids long. 
     Illustrative examples of linkers include glycine polymers (G)n; glycine-serine polymers (G 1-5 S 1-5 ) n , where n is an integer of at least one, two, three, four, or five; glycine-alanine polymers; alanine-serine polymers; and other flexible linkers known in the art. Glycine and glycine-serine polymers are relatively unstructured, and therefore may be able to serve as a neutral tether between domains of fusion proteins such as the CARs described herein. Glycine accesses significantly more phi-psi space than even alanine, and is much less restricted than residues with longer side chains (see Scheraga, Rev.  Computational Chem.  11173-142 (1992)). The ordinarily skilled artisan will recognize that design of a CAR in particular embodiments can include linkers that are all or partially flexible, such that the linker can include a flexible linker as well as one or more portions that confer less flexible structure to provide for a desired CAR structure. 
     Other exemplary linkers include, but are not limited to the following amino acid sequences: GGG (SEQ ID NO: 35); DGGGS (SEQ ID NO: 36); TGEKP (SEQ ID NO: 37) (see, e.g., Liu et al., PNAS 5525-5530 (1997)); GGRR (SEQ ID NO: 38) (Pomerantz et al. 1995, supra); (GGGGS) n  wherein=1, 2, 3, 4 or 5 (SEQ ID NO: 39) (Kim et al., PNAS 93, 1156-1160 (1996.); EGKSSGSGSESKVD (SEQ ID NO: 40) (Chaudhary et al., 1990, Proc. Natl. Acad. Sci. U.S.A. 87:1066-1070); KESGSVSSEQLAQFRSLD (SEQ ID NO: 41) (Bird et al., 1988, Science 242:423-426), GGRRGGGS (SEQ ID NO: 42); LRQRDGERP (SEQ ID NO: 43); LRQKDGGGSERP (SEQ ID NO: 44); LRQKD(GGGS) 2  ERP (SEQ ID NO: 45). Alternatively, flexible linkers can be rationally designed using a computer program capable of modeling both DNA-binding sites and the peptides themselves (Desjarlais &amp; Berg,  PNAS  90:2256-2260 (1993),  PNAS  91:11099-11103 (1994) or by phage display methods. In one embodiment, the linker comprises the following amino acid sequence: GSTSGSGKPGSGEGSTKG (SEQ ID NO: 46) (Cooper et al.,  Blood,  101(4): 1637-1644 (2003)). 
     3. Spacer Domain 
     In particular embodiments, the binding domain of the CAR is followed by one or more “spacer domains.” A “spacer domain,” refers to a polypeptide that separates two domains. In one embodiment, a spacer domain moves an antigen binding domain away from the effector cell surface to enable proper cell/cell contact, antigen binding and activation (Patel et al.,  Gene Therapy,  1999; 6: 412-419). The spacer domain may be derived either from a natural, synthetic, semi-synthetic, or recombinant source. In certain embodiments, a spacer domain is a portion of an immunoglobulin, including, but not limited to, one or more heavy chain constant regions, e.g., CH2 and CH3. The spacer domain can include the amino acid sequence of a naturally occurring immunoglobulin hinge region or an altered immunoglobulin hinge region. 
     In one embodiment, the spacer domain comprises the CH2 and CH3 domains of IgG1, IgG4, or IgD. 
     4. Hinge Domain 
     The binding domain of the CAR is generally followed by one or more “hinge domains.” A “hinge domain,” refers to a polypeptide that plays a role in positioning the antigen binding domain away from the effector cell surface to enable proper cell/cell contact, antigen binding and activation. In particular embodiments, a CAR comprises one or more hinge domains between the binding domain and the transmembrane domain (TM). The hinge domain may be derived either from a natural, synthetic, semi-synthetic, or recombinant source. The hinge domain can include the amino acid sequence of a naturally occurring immunoglobulin hinge region or an altered immunoglobulin hinge region. 
     An “altered hinge region” refers to (a) a naturally occurring hinge region with up to 30% amino acid changes (e.g., up to 25%, 20%, 15%, 10%, or 5% amino acid substitutions or deletions), (b) a portion of a naturally occurring hinge region that is at least 10 amino acids (e.g., at least 12, 13, 14 or 15 amino acids) in length with up to 30% amino acid changes (e.g., up to 25%, 20%, 15%, 10%, or 5% amino acid substitutions or deletions), or (c) a portion of a naturally occurring hinge region that comprises the core hinge region (which may be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, or at least 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 amino acids in length). In certain embodiments, one or more cysteine residues in a naturally occurring immunoglobulin hinge region may be substituted by one or more other amino acid residues (e.g., one or more serine residues). An altered immunoglobulin hinge region may alternatively or additionally have a proline residue of a wild type immunoglobulin hinge region substituted by another amino acid residue (e.g., a serine residue). 
     Illustrative hinge domains suitable for use in the CARs described herein include the hinge region derived from the extracellular regions of type 1 membrane proteins such as CD8α, and CD4, which may be wild-type hinge regions from these molecules or may be altered. In another embodiment, the hinge domain comprises a CD8α hinge region. 
     In one embodiment, the hinge is a PD-1 hinge or CD152 hinge. 
     5. Transmembrane (TM) Domain 
     A “transmembrane domain” is a domain that fuses the extracellular binding portion and intracellular signaling domain of a CAR and anchors the CAR to the plasma membrane of the immune effector cell. The TM domain may be derived either from a natural, synthetic, semi-synthetic, or recombinant source. The TM domain may be derived from (i.e., comprise at least the transmembrane region(s) of the alpha or beta chain of the T-cell receptor, CDδ, CD3ε, CDγ, CD3ζ, CD4, CDS, CD8α, CD9, CD 16, CD22, CD27, CD28, CD33, CD37, CD45, CD64, CD80, CD86, CD 134, CD137, CD152, CD154, and PD1. In a particular embodiment, the TM domain is synthetic and predominantly comprises hydrophobic residues such as leucine and valine. 
     In one embodiment, a CAR comprises a TM domain derived from, PD1, CD152, or CD8α. In another embodiment, a CAR comprises a TM domain derived from, PD1, CD152, or CD8α and a short oligo- or polypeptide linker, preferably between 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids in length that links the TM domain and the intracellular signaling domain of the CAR. A glycine-serine based linker provides a particularly suitable linker. In one embodiment, a CAR comprises a TM domain derived from CD8α and a short oligo- or polypeptide linker, preferably between 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 amino acids in length that links the TM domain and the intracellular signaling domain of the CAR. 
     6. Intracellular Signaling Domain 
     In particular embodiments, a CAR comprises an intracellular signaling domain. An “intracellular signaling domain,” refers to the part of a CAR that participates in transducing the message of effective CAR binding to target antigen(s) into the interior of the immune effector cell to elicit effector cell function, e.g., activation, cytokine production, proliferation and cytotoxic activity, including the release of cytotoxic factors to the CAR-bound target cell, or other cellular responses elicited with antigen binding to the extracellular CAR domain. 
     The term “effector function” refers to a specialized function of an immune effector cell. Effector function of the T cell, for example, may be cytolytic activity or help or activity including the secretion of a cytokine. Thus, the term “intracellular signaling domain” refers to the portion of a protein which transduces the effector function signal and that 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 domain. To the extent that a truncated portion of an intracellular signaling domain is used, such truncated portion may be used in place of the entire domain as long as it transduces the effector function signal. The term intracellular signaling domain is meant to include any truncated portion of the intracellular signaling domain sufficient to transducing effector function signal. 
     It is known that signals generated through the TCR alone are insufficient for full activation of the T cell and that a secondary or costimulatory signal is also required. Thus, T cell activation can be said to be mediated by two distinct classes of intracellular signaling domains: primary signaling domains that initiate antigen-dependent primary activation through the TCR (e.g., a TCR/CD3 complex) and costimulatory signaling domains that act in an antigen-independent manner to provide a secondary or costimulatory signal. In preferred embodiments, a CAR comprises an intracellular signaling domain that comprises one or more “costimulatory signaling domains” and a “primary signaling domain.” 
     In particular embodiments, a CAR comprises one or more costimulatory signaling domains to enhance the efficacy and expansion of T cells expressing CAR receptors. As used herein, the term, “costimulatory signaling domain,” or “costimulatory domain”, refers to an intracellular signaling domain of a costimulatory molecule. Costimulatory molecules are cell surface molecules other than antigen receptors or Fc receptors that provide a second signal required for efficient activation and function of T lymphocytes upon binding to antigen. Illustrative examples of such costimulatory molecules include TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR8, TLR9, TLR10, CARD11, CD2, CD7, CD27, CD28, CD30, CD40, CD54 (ICAM), CD83, CD134 (0X40), CD137 (4-1BB), CD278 (ICOS), DAP10, LAT, NKD2C, SLP76, TRIM, and ZAP70. 
     Primary signaling domains regulate primary activation of the TCR complex either in a stimulatory way, or in an inhibitory way. Primary signaling domains that act in a stimulatory manner may contain signaling motifs which are known as immunoreceptor tyrosine-based activation motifs or ITAMs. 
     Illustrative examples of ITAM containing primary signaling domains that are suitable for use in particular embodiments include those derived from FcRγ, FcRβ, CD3γ, CD3δ, CD3c, CD3, CD22, CD79a, CD79b, and CD66d. In particular preferred embodiments, a CAR comprises a CD3t primary signaling domain and one or more costimulatory signaling domains. The intracellular primary signaling and costimulatory signaling domains may be linked in any order in multivalent to the carboxyl terminus of the transmembrane domain. 
     In one embodiment, a CAR comprises one or more costimulatory signaling domains selected from the group consisting of CD28, CD137, and CD134, and a CD3ζ primary signaling domain. 
     In one embodiment, a CAR comprises a CD137 costimulatory signaling domain and a CD3ζ primary signaling domain. 
     In one embodiment, a CAR comprises a CD134 costimulatory signaling domain and a CD3ζ primary signaling domain. 
     In one embodiment, a CAR comprises a CD28 costimulatory signaling domain and a CD3ζ primary signaling domain. 
     D. Polypeptides 
     Various polypeptides are contemplated herein, including, but not limited to, multivalent CAR polypeptides, fragments, and domains thereof. In preferred embodiments, a polypeptide comprising one or more CARs is provided. In particular embodiments, a polypeptide comprises an amino acid sequence as set forth in any one of SEQ ID NOs: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, and 34. 
     “Polypeptide,” “peptide” and “protein” are used interchangeably, unless specified to the contrary, and according to conventional meaning, i.e., as a sequence of amino acids. In one embodiment, a “polypeptide” includes fusion polypeptides and other variants. Polypeptides can be prepared using any of a variety of well-known recombinant and/or synthetic techniques. Polypeptides are not limited to a specific length, e.g., they may comprise a full-length protein sequence, a fragment of a full-length protein, or a fusion protein, and may include post-translational modifications of the polypeptide, for example, glycosylations, acetylations, phosphorylations and the like, as well as other modifications known in the art, both naturally occurring and non-naturally occurring. 
     In various embodiments, the polypeptides comprise a signal (or leader) sequence at the N-terminal end of the protein, which co-translationally or post-translationally directs transfer of the protein. Illustrative examples of suitable signal sequences useful in polypeptides contemplated herein include, but are not limited to the IgG1 heavy chain signal polypeptide, a CD8a signal polypeptide, or a human GM-CSF receptor alpha signal polypeptide. Polypeptides can be prepared using any of a variety of well-known recombinant and/or synthetic techniques. Polypeptides contemplated herein specifically encompass sequences that have deletions from, additions to, and/or substitutions of one or more amino acids of a CAR contemplated herein. 
     An “isolated peptide” or an “isolated polypeptide” and the like, as used herein, refer to in vitro isolation and/or purification of a peptide or polypeptide molecule from a cellular environment, and from association with other components of the cell, i.e., it is not significantly associated with in vivo substances. In particular embodiments, an isolated polypeptide is a synthetic polypeptide, a semi-synthetic polypeptide, or a polypeptide obtained or derived from a recombinant source. 
     Polypeptides include “polypeptide variants.” Polypeptide variants may differ from a naturally occurring polypeptide in one or more substitutions, deletions, additions and/or insertions. Such variants may be naturally occurring or may be synthetically generated, for example, by modifying one or more of the above polypeptide sequences. For example, in particular embodiments, it may be desirable to improve the binding affinity and/or other biological properties of a polypeptide by introducing one or more substitutions, deletions, additions and/or insertions the polypeptide. In particular embodiments, polypeptides include polypeptides having at least about 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 86%, 97%, 98%, or 99% amino acid identity to any of the reference sequences contemplated herein, typically where the variant maintains at least one biological activity of the reference sequence. 
     Polypeptides variants include biologically active “polypeptide fragments.” Illustrative examples of biologically active polypeptide fragments include antigen binding domains, intracellular signaling domains, and the like. As used herein, the term “biologically active fragment” or “minimal biologically active fragment” refers to a polypeptide fragment that retains at least 100%, at least 90%, at least 80%, at least 70%, at least 60%, at least 50%, at least 40%, at least 30%, at least 20%, at least 10%, or at least 5% of the naturally occurring polypeptide activity. 
     In certain embodiments, a polypeptide fragment can comprise an amino acid chain at least 5 to about 1700 amino acids long. It will be appreciated that in certain embodiments, fragments are at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700 or more amino acids long. In particular embodiments, a polypeptide comprises a biologically active fragment of a CAR. 
     In particular embodiments, the polypeptides set forth herein may comprise one or more amino acids denoted as “X.” “X” if present in an amino acid SEQ ID NO, refers to any amino acid. One or more “X” residues may be present at the N- and C-terminus of an amino acid sequence set forth in particular SEQ ID NOs contemplated herein. If the “X” amino acids are not present the remaining amino acid sequence set forth in a SEQ ID NO may be considered a biologically active fragment. Particularly useful polypeptide fragments include functional domains, including antigen-binding domains or fragments of antibodies. 
     The polypeptide may also be fused in-frame or conjugated to a linker or other sequence for ease of synthesis, purification or identification of the polypeptide (e.g., poly-His), or to enhance binding of the polypeptide to a solid support. 
     As noted above, polypeptides may be altered in various ways including amino acid substitutions, deletions, truncations, and insertions. Methods for such manipulations are generally known in the art. For example, amino acid sequence variants of a reference polypeptide can be prepared by mutations in the DNA. Methods for mutagenesis and nucleotide sequence alterations are well known in the art. See, for example, Kunkel (1985,  Proc. Natl. Acad. Sci. USA.  82: 488-492), Kunkel et al., (1987,  Methods in Enzymol,  154: 367-382), U.S. Pat. No. 4,873,192, Watson, J. D. et al., ( Molecular Biology of the Gene , Fourth Edition, Benjamin/Cummings, Menlo Park, Calif, 1987) and the references cited therein. Guidance as to appropriate amino acid substitutions that do not affect biological activity of the protein of interest may be found in the model of Dayhoff et al., (1978)  Atlas of Protein Sequence and Structure  (Natl. Biomed. Res. Found., Washington, D.C.). 
     In certain embodiments, a polypeptide variant comprises one or more conservative substitutions. A “conservative substitution” is one in which an amino acid is substituted for another amino acid that has similar properties, such that one skilled in the art of peptide chemistry would expect the secondary structure and hydropathic nature of the polypeptide to be substantially unchanged. Modifications may be made in the structure of the polynucleotides and polypeptides contemplated in particular embodiments and still obtain a functional molecule that encodes a variant or derivative polypeptide with desirable characteristics. When it is desired to alter the amino acid sequence of a polypeptide to create an equivalent, or even an improved, variant polypeptide, one skilled in the art, for example, can change one or more of the codons of the encoding DNA sequence, e.g., according to Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Amino Acid Codons 
               
            
           
           
               
               
               
               
            
               
                   
                 One 
                 Three 
                   
               
               
                   
                 letter 
                 letter 
               
               
                 Amino Acids 
                 code 
                 code 
                 Codons 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Alanine 
                 A 
                 Ala 
                 GCA 
                 GCC 
                 GCG 
                 GCU 
               
            
           
           
               
               
               
               
               
            
               
                 Cysteine 
                 C 
                 Cys 
                 UGC 
                 UGU 
               
               
                 Aspartic acid 
                 D 
                 Asp 
                 GAC 
                 GAU 
               
               
                 Glutamic acid 
                 E 
                 Glu 
                 GAA 
                 GAG 
               
               
                 Phenylalanine 
                 F 
                 Phe 
                 UUC 
                 UUU 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Glycine 
                 G 
                 Gly 
                 GGA 
                 GGC 
                 GGG 
                 GGU 
               
            
           
           
               
               
               
               
               
            
               
                 Histidine 
                 H 
                 His 
                 CAC 
                 CAU 
               
            
           
           
               
               
               
               
               
               
            
               
                 Isoleucine 
                 I 
                 Iso 
                 AUA 
                 AUC 
                 AUU 
               
            
           
           
               
               
               
               
               
            
               
                 Lysine 
                 K 
                 Lys 
                 AAA 
                 AAG 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Leucine 
                 L 
                 Leu 
                 UUA 
                 UUG 
                 CUA 
                 CUC 
                 CUG 
                 CUU 
               
            
           
           
               
               
               
               
            
               
                 Methionine 
                 M 
                 Met 
                 AUG 
               
            
           
           
               
               
               
               
               
            
               
                 Asparagine 
                 N 
                 Asn 
                 AAC 
                 AAU 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Proline 
                 P 
                 Pro 
                 CCA 
                 CCC 
                 CCG 
                 CCU 
               
            
           
           
               
               
               
               
               
            
               
                 Glutamine 
                 Q 
                 Gln 
                 CAA 
                 CAG 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Arginine 
                 R 
                 Arg 
                 AGA 
                 AGG 
                 CGA 
                 CGC 
                 CGG 
                 CGU 
               
               
                 Serine 
                 S 
                 Ser 
                 AGC 
                 AGU 
                 UCA 
                 UCC 
                 UCG 
                 UCU 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Threonine 
                 T 
                 Thr 
                 ACA 
                 ACC 
                 ACG 
                 ACU 
               
               
                 Valine 
                 V 
                 Val 
                 GUA 
                 GUC 
                 GUG 
                 GUU 
               
            
           
           
               
               
               
               
            
               
                 Tryptophan 
                 W 
                 Trp 
                 UGG 
               
            
           
           
               
               
               
               
               
            
               
                 Tyrosine 
                 Y 
                 Tyr 
                 UAC 
                 UAU 
               
               
                   
               
            
           
         
       
     
     Guidance in determining which amino acid residues can be substituted, inserted, or deleted without abolishing biological activity can be found using computer programs well known in the art, such as DNASTAR, DNA Strider, Geneious, Mac Vector, or Vector NTI software. Preferably, amino acid changes in the protein variants disclosed herein are conservative amino acid changes, i.e., substitutions of similarly charged or uncharged amino acids. A conservative amino acid change involves substitution of one of a family of amino acids which are related in their side chains. Naturally occurring amino acids are generally divided into four families: acidic (aspartate, glutamate), basic (lysine, arginine, histidine), non-polar (alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), and uncharged polar (glycine, asparagine, glutamine, cysteine, serine, threonine, tyrosine) amino acids. Phenylalanine, tryptophan, and tyrosine are sometimes classified jointly as aromatic amino acids. In a peptide or protein, suitable conservative substitutions of amino acids are known to those of skill in this art and generally can be made without altering a biological activity of a resulting molecule. Those of skill in this art recognize that, in general, single amino acid substitutions in non-essential regions of a polypeptide do not substantially alter biological activity (see, e.g., Watson et al.  Molecular Biology of the Gene,  4th Edition, 1987, The Benjamin/Cummings Pub. Co., p. 224). 
     In one embodiment, where expression of two or more polypeptides is desired, the polynucleotide sequences encoding them can be separated by an IRES sequence as discussed elsewhere herein. In another embodiment, two or more polypeptides can be expressed as a fusion protein that comprises one or more self-cleaving polypeptide sequences. 
     Polypeptides contemplated in particular embodiments include fusion polypeptides. In preferred embodiments, fusion polypeptides and polynucleotides encoding fusion polypeptides are provided, e.g., multivalent CARs. Fusion polypeptides and fusion proteins refer to a polypeptide having at least two, three, four, five, six, seven, eight, nine, or ten or more polypeptide segments. Fusion polypeptides are typically linked C-terminus to N-terminus, although they can also be linked C-terminus to C-terminus, N-terminus to N-terminus, or N-terminus to C-terminus. The polypeptides of the fusion protein can be in any order or a specified order. Fusion polypeptides or fusion proteins can also include conservatively modified variants, polymorphic variants, alleles, mutants, subsequences, and interspecies homologs, so long as the desired transcriptional activity of the fusion polypeptide is preserved. Fusion polypeptides may be produced by chemical synthetic methods or by chemical linkage between the two moieties or may generally be prepared using other standard techniques. Ligated DNA sequences comprising the fusion polypeptide are operably linked to suitable transcriptional or translational control elements as discussed elsewhere herein. 
     In one embodiment, a fusion partner comprises a sequence that assists in expressing the protein (an expression enhancer) at higher yields than the native recombinant protein. Other fusion partners may be selected so as to increase the solubility of the protein or to enable the protein to be targeted to desired intracellular compartments or to facilitate transport of the fusion protein through the cell membrane. 
     Fusion polypeptides may further comprise a polypeptide cleavage signal between each of the polypeptide domains described herein. In addition, a polypeptide cleavage site can be put into any linker peptide sequence. Exemplary polypeptide cleavage signals include polypeptide cleavage recognition sites such as protease cleavage sites, nuclease cleavage sites (e.g., rare restriction enzyme recognition sites, self-cleaving ribozyme recognition sites), and self-cleaving viral oligopeptides (see deFelipe and Ryan, 2004.  Traffic,  5(8); 616-26). 
     Suitable protease cleavages sites and self-cleaving peptides are known to the skilled person (see, e.g., in Ryan et al., 1997.  J Gener. Virol.  78, 699-722; Scymczak et al. (2004)  Nature Biotech.  5, 589-594). Exemplary protease cleavage sites include, but are not limited to the cleavage sites of potyvirus NIa proteases (e.g., tobacco etch virus protease), potyvirus HC proteases, potyvirus P1 (P35) proteases, byovirus NIa proteases, byovirus RNA-2-encoded proteases, aphthovirus L proteases, enterovirus 2A proteases, rhinovirus 2A proteases, picorna 3C proteases, comovirus 24K proteases, nepovirus 24K proteases, RTSV (rice tungro spherical virus) 3C-like protease, PYVF (parsnip yellow fleck virus) 3C-like protease, heparin, thrombin, factor Xa and enterokinase. Due to its high cleavage stringency, TEV (tobacco etch virus) protease cleavage sites are preferred in one embodiment, e.g., EXXYXQ(G/S) (SEQ ID NO: 47), for example, ENLYFQG (SEQ ID NO: 48) and ENLYFQS (SEQ ID NO: 49) wherein X represents any amino acid (cleavage by TEV occurs between Q and G or Q and S). 
     In particular embodiments, the polypeptide cleavage signal is a viral self-cleaving peptide or ribosomal skipping sequence. 
     Illustrative examples of ribosomal skipping sequences include but are not limited to: a 2A or 2A-like site, sequence or domain (Donnelly et al., 2001.  J Gen. Virol.  82:1027-1041). In a particular embodiment, the viral 2A peptide is an aphthovirus 2A peptide, a potyvirus 2A peptide, or a cardiovirus 2A peptide. 
     In one embodiment, the viral 2A peptide is selected from the group consisting of: a foot-and-mouth disease virus (FMDV) 2A peptide, an equine rhinitis A virus (ERAV) 2A peptide, a Thosea asigna virus (TaV) 2A peptide, a porcine teschovirus-1 (PTV-1) 2A peptide, a Theilovirus 2A peptide, and an encephalomyocarditis virus 2A peptide. 
     Illustrative examples of 2A sites are provided in Table 2. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
             
            
               
                 SEQ ID NO: 50 
                 GSGATNFSLLKQAGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 51 
                 ATNFSLLKQAGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 52 
                 LLKQAGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 53 
                 GSGEGRGSLLTCGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 54 
                 EGRGSLLTCGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 55 
                 LLTCGDVEENPGP 
               
               
                   
               
               
                 SEQ ID NO: 56 
                 GSGQCTNYALLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 57 
                 QCTNYALLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 58 
                 LLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 59 
                 GSGVKQTLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 60 
                 VKQTLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 61 
                 LLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 62 
                 LLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 63 
                 TLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 64 
                 LLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 65 
                 NFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 66 
                 QLLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 67 
                 APVKQTLNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 68 
                 VTELLYRIVIKRAETYCPRPLLAIHPTEARHKQ 
               
               
                   
                 KIVAPVKQT 
               
               
                   
               
               
                 SEQ ID NO: 69 
                 LNFDLLKLAGDVESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 70 
                 LLAIHPTEARHKQKIVAPVKQTLNFDLLKLAGD 
               
               
                   
                 VESNPGP 
               
               
                   
               
               
                 SEQ ID NO: 71 
                 EARHKQKIVAPVKQTLNFDLLKLAGDVESNPGP 
               
               
                   
               
            
           
         
       
     
     In preferred embodiments, a polypeptide comprises a multivalent CAR polypeptide. 
     E. Polynucleotides 
     In particular embodiments, a polynucleotide encoding one or more polypeptides is provided. As used herein, the terms “polynucleotide” or “nucleic acid” refer to deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and DNA/RNA hybrids. Polynucleotides may be single-stranded or double-stranded and either recombinant, synthetic, or isolated. Polynucleotides include, but are not limited to: pre-messenger RNA (pre-mRNA), messenger RNA (mRNA), RNA, short interfering RNA (siRNA), short hairpin RNA (shRNA), microRNA (miRNA), ribozymes, genomic RNA (gRNA), plus strand RNA (RNA(+)), minus strand RNA (RNA(−)), tracrRNA, crRNA, single guide RNA (sgRNA), synthetic RNA, synthetic mRNA, genomic DNA (gDNA), PCR amplified DNA, complementary DNA (cDNA), synthetic DNA, or recombinant DNA. Polynucleotides refer to a polymeric form of nucleotides of at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 40, at least 50, at least 100, at least 200, at least 300, at least 400, at least 500, at least 1000, at least 5000, at least 10000, or at least 15000 or more nucleotides in length, either ribonucleotides or deoxyribonucleotides or a modified form of either type of nucleotide, as well as all intermediate lengths. It will be readily understood that “intermediate lengths, ” in this context, means any length between the quoted values, such as 6, 7, 8, 9, etc., 101, 102, 103, etc.; 151, 152, 153, etc.; 201, 202, 203, etc. In particular embodiments, polynucleotides or variants have at least or about 50%, 55%, 60%, 65%, 70%, 71%, 72%, 73%, 74%, 75%,76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%,85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% sequence identity to a reference sequence. 
     In particular embodiments, polynucleotides may be codon-optimized. As used herein, the term “codon-optimized” refers to substituting codons in a polynucleotide encoding a polypeptide in order to increase the expression, stability and/or activity of the polypeptide. Factors that influence codon optimization include, but are not limited to one or more of: (i) variation of codon biases between two or more organisms or genes or synthetically constructed bias tables, (ii) variation in the degree of codon bias within an organism, gene, or set of genes, (iii) systematic variation of codons including context, (iv) variation of codons according to their decoding tRNAs, (v) variation of codons according to GC %, either overall or in one position of the triplet, (vi) variation in degree of similarity to a reference sequence for example a naturally occurring sequence, (vii) variation in the codon frequency cutoff, (viii) structural properties of mRNAs transcribed from the DNA sequence, (ix) prior knowledge about the function of the DNA sequences upon which design of the codon substitution set is to be based, (x) systematic variation of codon sets for each amino acid, and/or (xi) isolated removal of spurious translation initiation sites. 
     In various illustrative embodiments, polynucleotides contemplated herein include those set forth in SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, and 33 and polynucleotides encoding the polypeptides set forth in SEQ ID NOs: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, and 34, polynucleotides encoding CAR polypeptides, expression vectors, viral vectors, and transfer plasmids. 
     As used herein, the terms “polynucleotide variant” and “variant” and the like refer to polynucleotides displaying substantial sequence identity with a reference polynucleotide sequence or polynucleotides that hybridize with a reference sequence under stringent conditions that are defined hereinafter. These terms also encompass polynucleotides that are distinguished from a reference polynucleotide by the addition, deletion, substitution, or modification of at least one nucleotide. Accordingly, the terms “polynucleotide variant” and “variant” include polynucleotides in which one or more nucleotides have been added or deleted, or modified, or replaced with different nucleotides. In this regard, it is well understood in the art that certain alterations inclusive of mutations, additions, deletions and substitutions can be made to a reference polynucleotide whereby the altered polynucleotide retains the biological function or activity of the reference polynucleotide. 
     The recitations “sequence identity” or, for example, comprising a “sequence 50% identical to,” as used herein, refer to the extent that sequences are identical on a nucleotide-by-nucleotide basis or an amino acid-by-amino acid basis over a window of comparison. Thus, a “percentage of sequence identity” may be calculated by comparing two optimally aligned sequences over the window of comparison, determining the number of positions at which the identical nucleic acid base (e.g., A, T, C, G, I) or the identical amino acid residue (e.g., Ala, Pro, Ser, Thr, Gly, Val, Leu, Ile, Phe, Tyr, Trp, Lys, Arg, His, Asp, Glu, Asn, Gln, Cys and Met) occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison (i.e., the window size), and multiplying the result by 100 to yield the percentage of sequence identity. Included are nucleotides and polypeptides having at least about 50%, 55%, 60%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 86%, 97%, 98%, or 99% sequence identity to any of the reference sequences described herein, typically where the polypeptide variant maintains at least one biological activity of the reference polypeptide. 
     Terms used to describe sequence relationships between two or more polynucleotides or polypeptides include “reference sequence,” “comparison window,” “sequence identity,” “percentage of sequence identity,” and “substantial identity”. A “reference sequence” is at least 12 but frequently 15 to 18 and often at least 25 monomer units, inclusive of nucleotides and amino acid residues, in length. Because two polynucleotides may each comprise (1) a sequence (i.e., only a portion of the complete polynucleotide sequence) that is similar between the two polynucleotides, and (2) a sequence that is divergent between the two polynucleotides, sequence comparisons between two (or more) polynucleotides are typically performed by comparing sequences of the two polynucleotides over a “comparison window” to identify and compare local regions of sequence similarity. A “comparison window” refers to a conceptual segment of at least 6 contiguous positions, usually about 50 to about 100, more usually about 100 to about 150 in which a sequence is compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned. The comparison window may comprise additions or deletions (i.e., gaps) of about 20% or less as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. Optimal alignment of sequences for aligning a comparison window may be conducted by computerized implementations of algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package Release 7.0, Genetics Computer Group, 575 Science Drive Madison, Wisc., USA) or by inspection and the best alignment (i.e., resulting in the highest percentage homology over the comparison window) generated by any of the various methods selected. Reference also may be made to the BLAST family of programs as for example disclosed by Altschul et al., 1997, Nucl. Acids Res. 25:3389. A detailed discussion of sequence analysis can be found in Unit 19.3 of Ausubel et al.,  Current Protocols in Molecular Biology , John Wiley &amp; Sons Inc, 1994-1998, Chapter 15. 
     An “isolated polynucleotide,” as used herein, refers to a polynucleotide that has been purified from the sequences which flank it in a naturally-occurring state, e.g., a DNA fragment that has been removed from the sequences that are normally adjacent to the fragment. In particular embodiments, an “isolated polynucleotide” refers to a complementary DNA (cDNA), a recombinant polynucleotide, a synthetic polynucleotide, or other polynucleotide that does not exist in nature and that has been made by the hand of man. In particular embodiments, an isolated polynucleotide is a synthetic polynucleotide, a semi-synthetic polynucleotide, or a polynucleotide obtained or derived from a recombinant source. 
     In various embodiments, a polynucleotide comprises an mRNA encoding a CAR polypeptide contemplated herein. 
     Terms that describe the orientation of polynucleotides include: 5′ (normally the end of the polynucleotide having a free phosphate group) and 3′ (normally the end of the polynucleotide having a free hydroxyl (OH) group). Polynucleotide sequences can be annotated in the 5′ to 3′ orientation or the 3′ to 5′ orientation. For DNA and mRNA, the 5′ to 3′ strand is designated the “sense,” “plus,” or “coding” strand because its sequence is identical to the sequence of the premessenger (premRNA) [except for uracil (U) in RNA, instead of thymine (T) in DNA]. For DNA and mRNA, the complementary 3′ to 5′ strand which is the strand transcribed by the RNA polymerase is designated as “template,” “antisense,” “minus,” or “non-coding” strand. As used herein, the term “reverse orientation” refers to a 5′ to 3′ sequence written in the 3′ to 5′ orientation or a 3′ to 5′ sequence written in the 5′ to 3′ orientation. 
     The terms “complementary” and “complementarity” refer to polynucleotides (i.e., a sequence of nucleotides) related by the base-pairing rules. For example, the complementary strand of the DNA sequence 5′ A G T C AT G 3′ is 3′ TC A G T AC 5′. The latter sequence is often written as the reverse complement with the 5′ end on the left and the 3′ end on the right, 5′ C A T G A C T 3′. A sequence that is equal to its reverse complement is said to be a palindromic sequence. Complementarity can be “partial,” in which only some of the nucleic acids&#39; bases are matched according to the base pairing rules. Or, there can be “complete” or “total” complementarity between the nucleic acids. 
     The term “nucleic acid cassette” or “expression cassette” as used herein refers to genetic sequences within the vector which can express an RNA, and subsequently a polypeptide. In one embodiment, the nucleic acid cassette contains a gene(s)-of-interest, e.g., a polynucleotide(s)-of-interest. In another embodiment, the nucleic acid cassette contains one or more expression control sequences, e.g., a promoter, enhancer, poly(A) sequence, and a gene(s)-of-interest, e.g., a polynucleotide(s)-of-interest. Vectors may comprise 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 or more nucleic acid cassettes. The nucleic acid cassette is positionally and sequentially oriented within the vector such that the nucleic acid in the cassette can be transcribed into RNA, and when necessary, translated into a protein or a polypeptide, undergo appropriate post-translational modifications required for activity in the transformed cell, and be translocated to the appropriate compartment for biological activity by targeting to appropriate intracellular compartments or secretion into extracellular compartments. Preferably, in some embodiments, the cassette has its 3′ and 5′ ends adapted for ready insertion into a vector and/or genome, e.g., it has restriction endonuclease sites at each end. In a preferred embodiment, the nucleic acid cassette encodes a multivalent CAR contemplated herein. The cassette can be removed and inserted into a plasmid or viral vector as a single unit. 
     Polynucleotides include polynucleotide(s)-of-interest. As used herein, the term “polynucleotide-of-interest” refers to a polynucleotide encoding a polypeptide or fusion polypeptide or a polynucleotide that serves as a template for the transcription of an inhibitory polynucleotide, as contemplated herein. 
     Moreover, it will be appreciated by those of ordinary skill in the art that, as a result of the degeneracy of the genetic code, there are many nucleotide sequences that may encode a polypeptide, or fragment of variant thereof, as contemplated herein. Some of these polynucleotides bear minimal homology to the nucleotide sequence of any native gene. Nonetheless, polynucleotides that vary due to differences in codon usage are specifically contemplated in particular embodiments, for example polynucleotides that are optimized for human and/or primate codon selection. In one embodiment, polynucleotides comprising particular allelic sequences are provided. Alleles are endogenous polynucleotide sequences that are altered as a result of one or more mutations, such as deletions, additions and/or substitutions of nucleotides. 
     The polynucleotides contemplated in particular embodiments, regardless of the length of the coding sequence itself, may be combined with other DNA sequences, such as promoters and/or enhancers, untranslated regions (UTRs), Kozak sequences, polyadenylation signals, additional restriction enzyme sites, multiple cloning sites, internal ribosomal entry sites (IRES), recombinase recognition sites (e.g., LoxP, FRT, and Att sites), termination codons, transcriptional termination signals, post-transcription response elements, and polynucleotides encoding self-cleaving polypeptides, epitope tags, as disclosed elsewhere herein or as known in the art, such that their overall length may vary considerably. It is therefore contemplated in particular embodiments that a polynucleotide fragment of almost any length may be employed, with the total length preferably being limited by the ease of preparation and use in the intended recombinant DNA protocol. 
     Polynucleotides can be prepared, manipulated, expressed and/or delivered using any of a variety of well-established techniques known and available in the art. In order to express a desired polypeptide, a nucleotide sequence encoding the polypeptide, can be inserted into appropriate vector. A desired polypeptide can also be expressed by delivering an mRNA encoding the polypeptide into the cell. 
     Illustrative examples of vectors include, but are not limited to plasmid, autonomously replicating sequences, and transposable elements, e.g., Sleeping Beauty, PiggyBac. 
     Additional illustrative examples of vectors include, without limitation, plasmids, phagemids, cosmids, artificial chromosomes such as yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC), or P1-derived artificial chromosome (PAC), bacteriophages such as lambda phage or M13 phage, and animal viruses. 
     Illustrative examples of viruses useful as vectors include, without limitation, retrovirus (including lentivirus), adenovirus, adeno-associated virus, herpesvirus (e.g., herpes simplex virus), poxvirus, baculovirus, papillomavirus, and papovavirus (e.g., SV40). 
     Illustrative examples of expression vectors include, but are not limited to pClneo vectors (Promega) for expression in mammalian cells; pLenti4/V5-DEST™, pLenti6/V5-DEST™, and pLenti6.2/V5-GW/lacZ (Invitrogen) for lentivirus-mediated gene transfer and expression in mammalian cells. In particular embodiments, coding sequences of polypeptides disclosed herein can be ligated into such expression vectors for the expression of the polypeptides in mammalian cells. 
     In particular embodiments, the vector is an episomal vector or a vector that is maintained extrachromosomally. As used herein, the term “episomal” refers to a vector that is able to replicate without integration into host&#39;s chromosomal DNA and without gradual loss from a dividing host cell also meaning that said vector replicates extrachromosomally or episomally. 
     “Expression control sequences,” “control elements,” or “regulatory sequences” present in an expression vector are those non-translated regions of the vector—origin of replication, selection cassettes, promoters, enhancers, translation initiation signals (Shine Dalgarno sequence or Kozak sequence) introns, post-transcriptional regulatory elements, a polyadenylation sequence, 5′ and 3′ untranslated regions—which interact with host cellular proteins to carry out transcription and translation. Such elements may vary in their strength and specificity. Depending on the vector system and host utilized, any number of suitable transcription and translation elements, including ubiquitous promoters and inducible promoters may be used. 
     In particular embodiments, a polynucleotide comprises a vector, including but not limited to expression vectors and viral vectors. A vector may comprise one or more exogenous, endogenous, or heterologous control sequences such as promoters and/or enhancers. An “endogenous control sequence” is one which is naturally linked with a given gene in the genome. An “exogenous control sequence” is one which is placed in juxtaposition to a gene by means of genetic manipulation (i.e., molecular biological techniques) such that transcription of that gene is directed by the linked enhancer/promoter. A “heterologous control sequence” is an exogenous sequence that is from a different species than the cell being genetically manipulated. A “synthetic” control sequence may comprise elements of one more endogenous and/or exogenous sequences, and/or sequences determined in vitro or in silico that provide optimal promoter and/or enhancer activity for the particular therapy. 
     The term “promoter” as used herein refers to a recognition site of a polynucleotide (DNA or RNA) to which an RNA polymerase binds. An RNA polymerase initiates and transcribes polynucleotides operably linked to the promoter. In particular embodiments, promoters operative in mammalian cells comprise an AT-rich region located approximately 25 to 30 bases upstream from the site where transcription is initiated and/or another sequence found 70 to 80 bases upstream from the start of transcription, a CNCAAT region where N may be any nucleotide. 
     The term “enhancer” refers to a segment of DNA which contains sequences capable of providing enhanced transcription and in some instances can function independent of their orientation relative to another control sequence. An enhancer can function cooperatively or additively with promoters and/or other enhancer elements. The term “promoter/enhancer” refers to a segment of DNA which contains sequences capable of providing both promoter and enhancer functions. 
     The term “operably linked”, refers to a juxtaposition wherein the components described are in a relationship permitting them to function in their intended manner. In one embodiment, the term refers to a functional linkage between a nucleic acid expression control sequence (such as a promoter, and/or enhancer) and a second polynucleotide sequence, e.g., a polynucleotide-of-interest, wherein the expression control sequence directs transcription of the nucleic acid corresponding to the second sequence. 
     As used herein, the term “constitutive expression control sequence” refers to a promoter, enhancer, or promoter/enhancer that continually or continuously allows for transcription of an operably linked sequence. A constitutive expression control sequence may be a “ubiquitous” promoter, enhancer, or promoter/enhancer that allows expression in a wide variety of cell and tissue types or a “cell specific,” “cell type specific,” “cell lineage specific,” or “tissue specific” promoter, enhancer, or promoter/enhancer that allows expression in a restricted variety of cell and tissue types, respectively. 
     Illustrative ubiquitous expression control sequences suitable for use in particular embodiments include, but are not limited to, a cytomegalovirus (CMV) immediate early promoter, a viral simian virus 40 (SV40) (e.g., early or late), a Moloney murine leukemia virus (MoMLV) LTR promoter, a Rous sarcoma virus (RSV) LTR, a herpes simplex virus (HSV) (thymidine kinase) promoter, H5, P7.5, and P11 promoters from vaccinia virus, a short elongation factor 1-alpha (EF1a-short) promoter, a long elongation factor 1-alpha (EF1a-long) promoter, early growth response 1 (EGR1), ferritin H (FerH), ferritin L (FerL), Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), eukaryotic translation initiation factor 4A1 (EIF4A1), heat shock 70 kDa protein 5 (HSPA5), heat shock protein 90 kDa beta, member 1 (HSP90B1), heat shock protein 70 kDa (HSP70), β-kinesin (β-KIN), the human ROSA 26 locus (Irions et al., Nature Biotechnology 25, 1477-1482 (2007)), a Ubiquitin C promoter (UBC), a phosphoglycerate kinase-1 (PGK) promoter, a cytomegalovirus enhancer/chicken β-actin (CAG) promoter, a β-actin promoter and a myeloproliferative sarcoma virus enhancer, negative control region deleted, d1587rev primer-binding site substituted (MND) U3 promoter (Haas et al.  Journal of Virology.  2003; 77(17): 9439-9450). 
     In a particular embodiment, it may be desirable to use a cell, cell type, cell lineage or tissue specific expression control sequence to achieve cell type specific, lineage specific, or tissue specific expression of a desired polynucleotide sequence (e.g., to express a particular nucleic acid encoding a polypeptide in only a subset of cell types, cell lineages, or tissues or during specific stages of development). 
     As used herein, “conditional expression” may refer to any type of conditional expression including, but not limited to, inducible expression; repressible expression; expression in cells or tissues having a particular physiological, biological, or disease state, etc. This definition is not intended to exclude cell type or tissue specific expression. Certain embodiments provide conditional expression of a polynucleotide-of-interest, e.g., expression is controlled by subjecting a cell, tissue, organism, etc., to a treatment or condition that causes the polynucleotide to be expressed or that causes an increase or decrease in expression of the polynucleotide encoded by the polynucleotide-of-interest. 
     Illustrative examples of inducible promoters/systems include, but are not limited to, steroid-inducible promoters such as promoters for genes encoding glucocorticoid or estrogen receptors (inducible by treatment with the corresponding hormone), metallothionine promoter (inducible by treatment with various heavy metals), MX-1 promoter (inducible by interferon), the “GeneSwitch” mifepristone-regulatable system (Sirin et al., 2003, Gene, 323:67), the cumate inducible gene switch (WO 2002/088346), tetracycline-dependent regulatory systems, etc. 
     Conditional expression can also be achieved by using a site-specific DNA recombinase. According to certain embodiments, polynucleotides comprises at least one (typically two) site(s) for recombination mediated by a site-specific recombinase. As used herein, the terms “recombinase” or “site-specific recombinase” include excisive or integrative proteins, enzymes, co-factors or associated proteins that are involved in recombination reactions involving one or more recombination sites (e.g., two, three, four, five, six, seven, eight, nine, ten or more.), which may be wild-type proteins (see Landy, Current Opinion in Biotechnology 3:699-707 (1993)), or mutants, derivatives (e.g., fusion proteins containing the recombination protein sequences or fragments thereof), fragments, and variants thereof. Illustrative examples of recombinases suitable for use in particular embodiments include, but are not limited to: Cre, Int, IHF, Xis, Flp, Fis, Hin, Gin, ΦC31, Cin, Tn3 resolvase, TndX, XerC, XerD, TnpX, Hjc, Gin, SpCCE1, and ParA. 
     The polynucleotides may comprise one or more recombination sites for any of a wide variety of site specific recombinases. It is to be understood that the target site for a site-specific recombinase is in addition to any site(s) required for integration of a vector, e.g., a retroviral vector or lentiviral vector. As used herein, the terms “recombination sequence,” “recombination site,” or “site specific recombination site” refer to a particular nucleic acid sequence to which a recombinase recognizes and binds. 
     For example, one recombination site for Cre recombinase is loxP which is a 34 base pair sequence comprising two 13 base pair inverted repeats (serving as the recombinase binding sites) flanking an 8 base pair core sequence (Sauer, B., Current Opinion in Biotechnology 5:521-527 (1994)). Other exemplary loxP sites include, but are not limited to: lox511 (Hoess et al., 1996; Bethke and Sauer, 1997), 1ox5171 (Lee and Saito, 1998), 1ox2272 (Lee and Saito, 1998), m2 (Langer et al., 2002), lox71 (Albert et al., 1995), and 1ox66 (Albert et al., 1995). 
     Suitable recognition sites for the FLP recombinase include, but are not limited to: FRT (McLeod, et al., 1996), F1, F2, F3 (Schlake and Bode, 1994), F4, F5 (Schlake and Bode, 1994), FRT(LE) (Senecoff et al., 1988), FRT(RE) (Senecoff et al., 1988). 
     Other examples of recognition sequences are the attB, attP, attL, and attR sequences, which are recognized by the recombinase enzyme λ Integrase, e.g., phi-c31. The φC31 SSR mediates recombination only between the heterotypic sites attB (34 bp in length) and attP (39 bp in length) (Groth et al., 2000). attB and attP, named for the attachment sites for the phage integrase on the bacterial and phage genomes, respectively, both contain imperfect inverted repeats that are likely bound by φC31 homodimers (Groth et al., 2000). The product sites, attL and attR, are effectively inert to further φC31-mediated recombination (Belteki et al., 2003), making the reaction irreversible. For catalyzing insertions, it has been found that attB-bearing DNA inserts into a genomic attP site more readily than an attP site into a genomic attB site (Thyagarajan et al., 2001; Belteki et al., 2003). Thus, typical strategies position by homologous recombination an attP-bearing “docking site” into a defined locus, which is then partnered with an attB-bearing incoming sequence for insertion. 
     In particular embodiments, polynucleotides contemplated herein, include one or more polynucleotides-of-interest that encode one or more polypeptides. In particular embodiments, to achieve efficient translation of each of the plurality of polypeptides, the polynucleotide sequences can be separated by one or more IRES sequences or polynucleotide sequences encoding self-cleaving polypeptides. 
     As used herein, an “internal ribosome entry site” or “IRES” refers to an element that promotes direct internal ribosome entry to the initiation codon, such as ATG, of a cistron (a protein encoding region), thereby leading to the cap-independent translation of the gene. See, e.g., Jackson et al., 1990. Trends Biochem Sci 15(12):477-83) and Jackson and Kaminski. 1995. RNA 1(10):985-1000. Examples of IRES generally employed by those of skill in the art include those described in U.S. Pat. No. 6,692,736. Further examples of “IRES” known in the art include, but are not limited to IRES obtainable from picornavirus (Jackson et al., 1990) and IRES obtainable from viral or cellular mRNA sources, such as for example, immunoglobulin heavy-chain binding protein (BiP), the vascular endothelial growth factor (VEGF) (Huez et al. 1998. Mol. Cell. Biol. 18(11):6178-6190), the fibroblast growth factor 2 (FGF-2), and insulin-like growth factor (IGFII), the translational initiation factor eIF4G and yeast transcription factors TFIID and HAP4, the encephelomycarditis virus (EMCV) which is commercially available from Novagen (Duke et al., 1992. J. Virol 66(3):1602-9) and the VEGF IRES (Huez et al., 1998. Mol Cell Biol 18(11):6178-90). IRES have also been reported in viral genomes of Picornaviridae, Dicistroviridae and Flaviviridae species and in HCV, Friend murine leukemia virus (FrMLV) and Moloney murine leukemia virus (MoMLV). 
     In one embodiment, the IRES used in polynucleotides contemplated herein is an EMCV IRES. 
     In particular embodiments, the polynucleotides comprise polynucleotides that have a consensus Kozak sequence and that encode a desired polypeptide. As used herein, the term “Kozak sequence” refers to a short nucleotide sequence that greatly facilitates the initial binding of mRNA to the small subunit of the ribosome and increases translation. The consensus Kozak sequence is (GCC)RCCATGG (SEQ ID NO:72), where R is a purine (A or G) (Kozak, 1986.  Cell.  44(2):283-92, and Kozak, 1987.  Nucleic Acids Res.  15(20):8125-48). 
     Elements directing the efficient termination and polyadenylation of the heterologous nucleic acid transcripts increases heterologous gene expression. Transcription termination signals are generally found downstream of the polyadenylation signal. In particular embodiments, vectors comprise a polyadenylation sequence 3′ of a polynucleotide encoding a polypeptide to be expressed. The term “polyA site” or “polyA sequence” as used herein denotes a DNA sequence which directs both the termination and polyadenylation of the nascent RNA transcript by RNA polymerase II. Polyadenylation sequences can promote mRNA stability by addition of a polyA tail to the 3′ end of the coding sequence and thus, contribute to increased translational efficiency. Cleavage and polyadenylation is directed by a poly(A) sequence in the RNA. The core poly(A) sequence for mammalian pre-mRNAs has two recognition elements flanking a cleavage-polyadenylation site. Typically, an almost invariant AAUAAA hexamer lies 20-50 nucleotides upstream of a more variable element rich in U or GU residues. Cleavage of the nascent transcript occurs between these two elements and is coupled to the addition of up to 250 adenosines to the 5′ cleavage product. In particular embodiments, the core poly(A) sequence is an ideal polyA sequence (e.g., AATAAA, ATTAAA, AGTAAA). In particular embodiments, the poly(A) sequence is an SV40 polyA sequence, a bovine growth hormone polyA sequence (BGHpA), a rabbit β-globin polyA sequence (rβgpA), or another suitable heterologous or endogenous polyA sequence known in the art. In particular embodiments, the poly(A) sequence is synthetic. 
     In some embodiments, a polynucleotide or cell harboring the polynucleotide utilizes a suicide gene, including an inducible suicide gene to reduce the risk of direct toxicity and/or uncontrolled proliferation. In specific embodiments, the suicide gene is not immunogenic to the host harboring the polynucleotide or cell. A certain example of a suicide gene that may be used is caspase-9 or caspase-8 or cytosine deaminase. Caspase-9 can be activated using a specific chemical inducer of dimerization (CID). 
     In certain embodiments, polynucleotides comprise gene segments that cause the genetically modified cells contemplated herein to be susceptible to negative selection in vivo. “Negative selection” refers to an infused cell that can be eliminated as a result of a change in the in vivo condition of the individual. The negative selectable phenotype may result from the insertion of a gene that confers sensitivity to an administered agent, for example, a compound. Negative selection genes are known in the art, and include, but are not limited to: the Herpes simplex virus type I thymidine kinase (HSV-I TK) gene which confers ganciclovir sensitivity; the cellular hypoxanthine phosphribosyltransferase (HPRT) gene, the cellular adenine phosphoribosyltransferase (APRT) gene, and bacterial cytosine deaminase. 
     In some embodiments, genetically modified cells comprise a polynucleotide further comprising a positive marker that enables the selection of cells of the negative selectable phenotype in vitro. The positive selectable marker may be a gene, which upon being introduced into the host cell, expresses a dominant phenotype permitting positive selection of cells carrying the gene. Genes of this type are known in the art, and include, but are not limited to hygromycin-B phosphotransferase gene (hph) which confers resistance to hygromycin B, the amino glycoside phosphotransferase gene (neo or aph) from Tn5 which codes for resistance to the antibiotic G418, the dihydrofolate reductase (DHFR) gene, the adenosine deaminase gene (ADA), and the multi-drug resistance (MDR) gene. 
     In one embodiment, the positive selectable marker and the negative selectable element are linked such that loss of the negative selectable element necessarily also is accompanied by loss of the positive selectable marker. In a particular embodiment, the positive and negative selectable markers are fused so that loss of one obligatorily leads to loss of the other. An example of a fused polynucleotide that yields as an expression product a polypeptide that confers both the desired positive and negative selection features described above is a hygromycin phosphotransferase thymidine kinase fusion gene (HyTK). Expression of this gene yields a polypeptide that confers hygromycin B resistance for positive selection in vitro, and ganciclovir sensitivity for negative selection in vivo. See also the publications of PCT US91/08442 and PCT/US94/05601, by S. D. Lupton, describing the use of bifunctional selectable fusion genes derived from fusing a dominant positive selectable marker with negative selectable markers. 
     Preferred positive selectable markers are derived from genes selected from the group consisting of hph, nco, and gpt, and preferred negative selectable markers are derived from genes selected from the group consisting of cytosine deaminase, HSV-I TK, VZV TK, HPRT, APRT and gpt. Exemplary bifunctional selectable fusion genes contemplated in particular embodiments include but are not limited to genes wherein the positive selectable marker is derived from hph or neo, and the negative selectable marker is derived from cytosine deaminase or a TK gene or selectable marker. 
     In particular embodiments, polynucleotides encoding one or more multivalent CARs may be introduced into hematopoietic cells, e.g., T cells, by both non-viral and viral methods. 
     The term “vector” is used herein to refer to a nucleic acid molecule capable transferring or transporting another nucleic acid molecule. The transferred nucleic acid is generally linked to, e.g., inserted into, the vector nucleic acid molecule. A vector may include sequences that direct autonomous replication in a cell, or may include sequences sufficient to allow integration into host cell DNA. In particular embodiments, non-viral vectors are used to deliver one or more polynucleotides contemplated herein to a T cell. 
     Illustrative examples of non-viral vectors include, but are not limited to plasmids (e.g., DNA plasmids or RNA plasmids), transposons, cosmids, and bacterial artificial chromosomes. 
     Illustrative methods of non-viral delivery of polynucleotides contemplated in particular embodiments include, but are not limited to: electroporation, sonoporation, lipofection, microinjection, biolistics, virosomes, liposomes, immunoliposomes, nanoparticles, polycation or lipid:nucleic acid conjugates, naked DNA, artificial virions, DEAE-dextran-mediated transfer, gene gun, and heat-shock. 
     Illustrative examples of polynucleotide delivery systems suitable for use in particular embodiments contemplated in particular embodiments include, but are not limited to those provided by Amaxa Biosystems, Maxcyte, Inc., BTX Molecular Delivery Systems, and Copernicus Therapeutics Inc. Lipofection reagents are sold commercially (e.g., Transfectam™ and Lipofectin™). Cationic and neutral lipids that are suitable for efficient receptor-recognition lipofection of polynucleotides have been described in the literature. See e.g., Liu et al. (2003) Gene Therapy. 10:180-187; and Balazs et al. (2011) Journal of Drug Delivery. 2011:1-12. Antibody-targeted, bacterially derived, non-living nanocell-based delivery is also contemplated in particular embodiments. 
     Viral vectors comprising polynucleotides contemplated in particular embodiments can be delivered in vivo by administration to an individual patient, typically by systemic administration (e.g., intravenous, intraperitoneal, intramuscular, subdermal, or intracranial infusion) or topical application, as described below. Alternatively, vectors can be delivered to cells ex vivo, such as cells explanted from an individual patient (e.g., mobilized peripheral blood, lymphocytes, bone marrow aspirates, tissue biopsy, etc.) or universal donor hematopoietic stem cells, followed by reimplantation of the cells into a patient. 
     In one embodiment, viral vectors comprising multivalent CARs are administered directly to an organism for transduction of cells in vivo. Alternatively, naked DNA can be administered. Administration is by any of the routes normally used for introducing a molecule into ultimate contact with blood or tissue cells including, but not limited to, injection, infusion, topical application and electroporation. Suitable methods of administering such nucleic acids are available and well known to those of skill in the art, and, although more than one route can be used to administer a particular composition, a particular route can often provide a more immediate and more effective reaction than another route. 
     Illustrative examples of viral vector systems suitable for use in particular embodiments contemplated herein include but are not limited to adeno-associated virus (AAV), retrovirus, herpes simplex virus, adenovirus, and vaccinia virus vectors. 
     In various embodiments, one or more polynucleotides encoding a multivalent CAR are introduced into a hematopoietic cell, e.g., a T cell, by transducing the cell with a recombinant adeno-associated virus (rAAV), comprising the one or more polynucleotides. 
     AAV is a small (˜26 nm) replication-defective, primarily episomal, non-enveloped virus. AAV can infect both dividing and non-dividing cells and may incorporate its genome into that of the host cell. Recombinant AAV (rAAV) are typically composed of, at a minimum, a transgene and its regulatory sequences, and 5′ and 3′ AAV inverted terminal repeats (ITRs). The ITR sequences are about 145 bp in length. In particular embodiments, the rAAV comprises ITRs and capsid sequences isolated from AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, or AAV10. 
     In some embodiments, a chimeric rAAV is used the ITR sequences are isolated from one AAV serotype and the capsid sequences are isolated from a different AAV serotype. For example, a rAAV with ITR sequences derived from AAV2 and capsid sequences derived from AAV6 is referred to as AAV2/AAV6. In particular embodiments, the rAAV vector may comprise ITRs from AAV2, and capsid proteins from any one of AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, or AAV10. In a preferred embodiment, the rAAV comprises ITR sequences derived from AAV2 and capsid sequences derived from AAV6. In a preferred embodiment, the rAAV comprises ITR sequences derived from AAV2 and capsid sequences derived from AAV2. 
     In some embodiments, engineering and selection methods can be applied to AAV capsids to make them more likely to transduce cells of interest. 
     Construction of rAAV vectors, production, and purification thereof have been disclosed, e.g., in U.S. Pat. Nos. 9,169,494; 9,169,492; 9,012,224; 8,889,641; 8,809,058; and 8,784,799, each of which is incorporated by reference herein, in its entirety. 
     In various embodiments, one or more polynucleotides encoding a multivalent CAR are introduced into a hematopoietic cell, by transducing the cell with a retrovirus, e.g., lentivirus, comprising the one or more polynucleotides. 
     As used herein, the term “retrovirus” refers to an RNA virus that reverse transcribes its genomic RNA into a linear double-stranded DNA copy and subsequently covalently integrates its genomic DNA into a host genome. Illustrative retroviruses suitable for use in particular embodiments, include, but are not limited to: Moloney murine leukemia virus (M-MuLV), Moloney murine sarcoma virus (MoMSV), Harvey murine sarcoma virus (HaMuSV), murine mammary tumor virus (MuMTV), gibbon ape leukemia virus (GaLV), feline leukemia virus (FLV), spumavirus, Friend murine leukemia virus, Murine Stem Cell Virus (MSCV) and Rous Sarcoma Virus (RSV)) and lentivirus. 
     As used herein, the term “lentivirus” refers to a group (or genus) of complex retroviruses. Illustrative lentiviruses include, but are not limited to: HIV (human immunodeficiency virus; including HIV type 1, and HIV 2); visna-maedi virus (VMV) virus; the caprine arthritis-encephalitis virus (CAEV); equine infectious anemia virus (EIAV); feline immunodeficiency virus (FIV); bovine immune deficiency virus (BIV); and simian immunodeficiency virus (SIV). In one embodiment, HIV based vector backbones (i.e., HIV cis-acting sequence elements) are preferred. 
     In various embodiments, a lentiviral vector contemplated herein comprises one or more LTRs, and one or more, or all, of the following accessory elements: a cPPT/FLAP, a Psi (ψ) packaging signal, an export element, a promoter active in immune effector cells operably linked to a multivalent CAR, poly (A) sequences, and may optionally comprise a WPRE or 
     HPRE, an insulator element, a selectable marker, and a cell suicide gene, as discussed elsewhere herein. 
     In particular embodiments, lentiviral vectors contemplated herein may be integrative or non-integrating or integration defective lentivirus. As used herein, the term “integration defective lentivirus” or “IDLV” refers to a lentivirus having an integrase that lacks the capacity to integrate the viral genome into the genome of the host cells. Integration-incompetent viral vectors have been described in patent application WO 2006/010834, which is herein incorporated by reference in its entirety. 
     Illustrative mutations in the HIV-1 pol gene suitable to reduce integrase activity include, but are not limited to: H12N, H12C, H16C, H16V, S81 R, D41A, K42A, H51A, Q53C, D55V, D64E, D64V, E69A, K71A, E85A, E87A, D116N, D1161, D116A, N120G, N1201, N120E, E152G, E152A, D35E, K156E, K156A, E157A, K159E, K159A, K160A, R166A, D167A, E170A, H171A, K173A, K186Q, K186T, K188T, E198A, R199c, R199T, R199A, D202A, K211A, Q214L, Q216L, Q221 L, W235F, W235E, K236S, K236A, K246A, G247W, D253A, R262A, R263A and K264H. 
     In one embodiment, the HIV-1 integrase deficient pol gene comprises a D64V, D1161, D116A, E152G, or E152A mutation; D64V, D1161, and E152G mutations; or D64V, D116A, and E152A mutations. 
     In one embodiment, the HIV-1 integrase deficient pol gene comprises a D64V mutation. 
     The term “long terminal repeat (LTR)” refers to domains of base pairs located at the ends of retroviral DNAs which, in their natural sequence context, are direct repeats and contain U3, R and U5 regions. 
     As used herein, the term “FLAP element” or “cPPT/FLAP” refers to a nucleic acid whose sequence includes the central polypurine tract and central termination sequences (cPPT and CTS) of a retrovirus, e.g., HIV-1 or HIV-2. Suitable FLAP elements are described in U.S. Pat. No. 6,682,907 and in Zennou, et al., 2000, Cell, 101:173. In another embodiment, a lentiviral vector contains a FLAP element with one or more mutations in the cPPT and/or CTS elements. In yet another embodiment, a lentiviral vector comprises either a cPPT or CTS element. In yet another embodiment, a lentiviral vector does not comprise a cPPT or CTS element. 
     As used herein, the term “packaging signal” or “packaging sequence” refers to psi NI sequences located within the retroviral genome which are required for insertion of the viral RNA into the viral capsid or particle, see e.g., Clever et al., 1995. J. of Virology, Vol. 69, No. 4; pp. 2101-2109. 
     The term “export element” refers to a cis-acting post-transcriptional regulatory element which regulates the transport of an RNA transcript from the nucleus to the cytoplasm of a cell. Examples of RNA export elements include, but are not limited to, the human immunodeficiency virus (HIV) rev response element (RRE) (see e.g., Cullen et al., 1991. J. Virol. 65: 1053; and Cullen et al., 1991. Cell 58: 423), and the hepatitis B virus post-transcriptional regulatory element (HPRE). 
     In particular embodiments, expression of heterologous sequences in viral vectors is increased by incorporating posttranscriptional regulatory elements, efficient polyadenylation sites, and optionally, transcription termination signals into the vectors. A variety of posttranscriptional regulatory elements can increase expression of a heterologous nucleic acid at the protein, e.g., woodchuck hepatitis virus posttranscriptional regulatory element (WPRE; Zufferey et al., 1999, J. Virol., 73:2886); the posttranscriptional regulatory element present in hepatitis B virus (HPRE) (Huang et al., Mol. Cell. Biol., 5:3864); and the like (Liu et al., 1995, Genes Dev., 9:1766). 
     Lentiviral vectors preferably contain several safety enhancements as a result of modifying the LTRs. “Self-inactivating” (SIN) vectors refers to replication-defective vectors, e.g., in which the right (3′) LTR enhancer-promoter region, known as the U3 region, has been modified (e.g., by deletion or substitution) to prevent viral transcription beyond the first round of viral replication. An additional safety enhancement is provided by replacing the U3 region of the 5′ LTR with a heterologous promoter to drive transcription of the viral genome during production of viral particles. Examples of heterologous promoters which can be used include, for example, viral simian virus 40 (SV40) (e.g., early or late), cytomegalovirus (CMV) (e.g., immediate early), Moloney murine leukemia virus (MoMLV), Rous sarcoma virus (RSV), and herpes simplex virus (HSV) (thymidine kinase) promoters. 
     The terms “pseudotype” or “pseudotyping” as used herein, refer to a virus whose viral envelope proteins have been substituted with those of another virus possessing preferable characteristics. For example, HIV can be pseudotyped with vesicular stomatitis virus G-protein (VSV-G) envelope proteins, which allows HIV to infect a wider range of cells because HIV envelope proteins (encoded by the env gene) normally target the virus to CD4+ presenting cells. 
     In certain embodiments, lentiviral vectors are produced according to known methods. See e.g., Kutner et al., BMC Biotechnol. 2009;9:10. doi: 10.1186/1472-6750-9-10; Kutner et al. Nat. Protoc. 2009;4(4):495-505. doi: 10.1038/nprot.2009.22. 
     According to certain specific embodiments contemplated herein, most or all of the viral vector backbone sequences are derived from a lentivirus, e.g., HIV-1. However, it is to be understood that many different sources of retroviral and/or lentiviral sequences can be used, or combined and numerous substitutions and alterations in certain of the lentiviral sequences may be accommodated without impairing the ability of a transfer vector to perform the functions described herein. Moreover, a variety of lentiviral vectors are known in the art, see Naldini et al., (1996a, 1996b, and 1998); Zufferey et al., (1997); Dull et al., 1998, U.S. Pat. Nos. 6,013,516; and 5,994,136, many of which may be adapted to produce a viral vector or transfer plasmid contemplated herein. 
     In various embodiments, one or more polynucleotides encoding a multivalent CAR are introduced into a hematopoietic cell by transducing the cell with an adenovirus comprising the one or more polynucleotides. 
     Adenoviral based vectors are capable of very high transduction efficiency in many cell types and do not require cell division. With such vectors, high titer and high levels of expression have been obtained. This vector can be produced in large quantities in a relatively simple system. Most adenovirus vectors are engineered such that a transgene replaces the Ad E1a, E1b, and/or E3 genes; subsequently the replication defective vector is propagated in human 293 cells that supply deleted gene function in trans. Ad vectors can transduce multiple types of tissues in vivo, including non-dividing, differentiated cells such as those found in liver, kidney and muscle. Conventional Ad vectors have a large carrying capacity. 
     Generation and propagation of the current adenovirus vectors, which are replication deficient, may utilize a unique helper cell line, designated 293, which was transformed from human embryonic kidney cells by Ad5 DNA fragments and constitutively expresses E1 proteins (Graham et al., 1977). Since the E3 region is dispensable from the adenovirus genome (Jones &amp; Shenk, 1978), the current adenovirus vectors, with the help of 293 cells, carry foreign DNA in either the E1, the D3 or both regions (Graham &amp; Prevec, 1991). Adenovirus vectors have been used in eukaryotic gene expression (Levrero et al., 1991; Gomez-Foix et al., 1992) and vaccine development (Grunhaus &amp; Horwitz, 1992; Graham &amp; Prevec, 1992). Studies in administering recombinant adenovirus to different tissues include trachea instillation (Rosenfeld et al., 1991; Rosenfeld et al., 1992), muscle injection (Ragot et al., 1993), peripheral intravenous injections (Herz &amp; Gerard, 1993) and stereotactic inoculation into the brain (Le Gal La Salle et al., 1993). An example of the use of an Ad vector in a clinical trial involved polynucleotide therapy for antitumor immunization with intramuscular injection (Sterman et al., Hum. Gene Ther. 7:1083-9 (1998)). 
     In various embodiments, one or more polynucleotides encoding a multivalent CAR are introduced into a hematopoietic cell by transducing the cell with a herpes simplex virus, e.g., HSV-1, HSV-2, comprising the one or more polynucleotides. 
     The mature HSV virion consists of an enveloped icosahedral capsid with a viral genome consisting of a linear double-stranded DNA molecule that is 152 kb. In one embodiment, the HSV based viral vector is deficient in one or more essential or non-essential HSV genes. In one embodiment, the HSV based viral vector is replication deficient. Most replication deficient HSV vectors contain a deletion to remove one or more intermediate-early, early, or late HSV genes to prevent replication. For example, the HSV vector may be deficient in an immediate early gene selected from the group consisting of: ICP4, ICP22, ICP27, ICP47, and a combination thereof. Advantages of the HSV vector are its ability to enter a latent stage that can result in long-term DNA expression and its large viral DNA genome that can accommodate exogenous DNA inserts of up to 25 kb. HSV-based vectors are described in, for example, U.S. Pat. Nos. 5,837,532, 5,846,782, and 5,804,413, and International Patent Applications WO 91/02788, WO 96/04394, WO 98/15637, and WO 99/06583, each of which are incorporated by reference herein in its entirety. 
     F. Genetically Modified Cells 
     In various embodiments, cells are modified to express the multivalent CARs contemplated herein, for use in the treatment of immune disorders are provided. Cells may be non-genetically modified to express the CARs contemplated herein, or in particular preferred embodiments, cells may be genetically modified to express the CARs contemplated herein. As used herein, the term “genetically engineered” or “genetically modified” refers to the addition of extra genetic material in the form of DNA or RNA into the total genetic material in a cell. The terms, “genetically modified cells,” “modified cells,” and “redirected cells,” are used interchangeably in particular embodiments. As used herein, the term “gene therapy” refers to the introduction of extra genetic material in the form of DNA or RNA into the total genetic material in a cell that restores, corrects, or modifies expression of a gene, or for the purpose of expressing a CAR polypeptide. An “isolated cell” refers to a cell that has been obtained from an in vivo tissue or organ and is substantially free of extracellular matrix. 
     In particular embodiments, the multivalent CARs contemplated herein are introduced and expressed in immune effector cells so as to redirect their specificity to cells expressing target antigen(s). In particular embodiments, multivalent CARs contemplated herein are introduced and expressed in immune effector cells so as to redirect their specificity to a first target antigen and a second target antigen. 
     An “immune effector cell,” is any cell of the immune system that has one or more effector functions (e.g., cytotoxic cell killing activity, secretion of cytokines, induction of ADCC and/or CDC). The illustrative immune effector cells contemplated herein are T lymphocytes, in particular, cytotoxic T cells (CTLs; CD8+ T cells), TILs, and helper T cells (HTLs; CD4+ T cells). In one embodiment, immune effector cells include natural killer (NK) cells. In one embodiment, immune effector cells include natural killer T (NKT) cells. Immune effector cells can be autologous/autogeneic (“self”) or non-autologous (“non-self,” e.g., allogeneic, syngeneic or xenogeneic). 
     “Autologous,” as used herein, refers to cells from the same subject. “Allogeneic,” as used herein, refers to cells of the same species that differ genetically to the cell in comparison. “Syngeneic,” as used herein, refers to cells of a different subject that are genetically identical to the cell in comparison. “Xenogeneic,” as used herein, refers to cells of a different species to the cell in comparison. In preferred embodiments, the cells are autologous. 
     Illustrative immune effector cells used with the CARs contemplated herein include T lymphocytes. The terms “T cell” or “T lymphocyte” are art-recognized and are intended to include thymocytes, immature T lymphocytes, mature T lymphocytes, resting T lymphocytes, or activated T lymphocytes. A T cell can be a T helper (Th) cell, for example a T helper 1 (Th1) or a T helper 2 (Th2) cell. The T cell can be a helper T cell (HTL; CD4 +  T cell) CD4 +  T cell, a cytotoxic T cell (CTL; CD8 +  T cell), CD4 +  CD8 +  T cell, CD4 − CD8 −  T cell, or any other subset of T cells. Other illustrative populations of T cells suitable for use in particular embodiments include naïve T cells and memory T cells. In preferred embodiments, the T lymphocyte expresses CD62L. 
     As would be understood by the skilled person, other cells may also be used as immune effector cells with the CARs contemplated herein. In particular embodiments, immune effector cells also include NK cells, NKT cells, neutrophils, or macrophages. In some embodiments, immune effector cells also include progenitors of effector cells wherein such progenitor cells can be induced to differentiate into an immune effector cells in vivo or in vitro. Thus, in particular embodiments, immune effector cell includes progenitors of immune effectors cells such as hematopoietic stem cells (HSCs) contained within the CD34 +  population of cells derived from cord blood, bone marrow or mobilized peripheral blood which upon administration in a subject differentiate into mature immune effector cells, or which can be induced in vitro to differentiate into mature immune effector cells. 
     As used herein, immune effector cells genetically engineered to contain a specific CAR may be referred to as, “antigen specific redirected immune effector cells.” 
     The term, “CD34 +  cell,” as used herein refers to a cell expressing the CD34 protein on its cell surface. “CD34,” as used herein refers to a cell surface glycoprotein (e.g., sialomucin protein) that often acts as a cell-cell adhesion factor and is involved in T cell entrance into lymph nodes. The CD34 +  cell population contains hematopoietic stem cells (HSC), which upon administration to a patient differentiate and contribute to all hematopoietic lineages, including T cells, NK cells, NKT cells, neutrophils and cells of the monocyte/macrophage lineage. 
     Methods for making the immune effector cells which express a CAR contemplated herein are provided in particular embodiments. In one embodiment, the method comprises transfecting or transducing immune effector cells isolated from an individual such that the immune effector cells express one or more CARs as contemplated herein. In one embodiment, the method comprises transfecting or transducing immune effector cells isolated from an individual such that the immune effector cells express one or more CARs contemplated herein. In certain embodiments, the immune effector cells are isolated from an individual and genetically modified without further manipulation in vitro. Such cells can then be directly re-administered into the individual. In further embodiments, the immune effector cells are first activated and stimulated to proliferate in vitro prior to being genetically modified. In this regard, the immune effector cells may be cultured before and/or after being genetically modified. 
     In particular embodiments, prior to in vitro manipulation or genetic modification of the immune effector cells described herein, the source of cells is obtained from a subject. In particular embodiments, the modified immune effector cells comprise T cells. 
     T cells can be obtained from a number of sources including, but not limited to, peripheral blood mononuclear cells, bone marrow, lymph nodes tissue, cord blood, thymus issue, tissue from a site of infection, ascites, pleural effusion, spleen tissue, and tumors. In certain embodiments, T cells can be obtained from a unit of blood collected from a subject using any number of techniques known to the skilled person, such as sedimentation, e.g., FICOLL™ separation. 
     In other embodiments, an isolated or purified population of T cells is used. In some embodiments, after isolation of PBMC, both cytotoxic and helper T lymphocytes can be sorted into naive, memory, and effector T cell subpopulations either before or after activation, expansion, and/or genetic modification. 
     A specific subpopulation of T cells, expressing one or more of the following markers: CD3, CD4, CD8, CD28, CD45RA, CD45RO, CD62, CD127, and HLA-DR can be further isolated by positive or negative selection techniques. In one embodiment, a specific subpopulation of T cells, expressing one or more of the markers selected from the group consisting of CD62L, CCR7, CD28, CD27, CD122, CD127, CD197; or CD38 or CD62L, CD127, CD197, and CD38, is further isolated by positive or negative selection techniques. In various embodiments, the manufactured T cell compositions do not express or do not substantially express one or more of the following markers: CD57, CD244, CD160, PD-1, CTLA4, TIM3, and LAG3. 
     In one embodiment, an isolated or purified population of T cells expresses one or more of the markers including, but not limited to a CD3 + , CD4 + , CD8 + , or a combination thereof 
     In certain embodiments, the T cells are isolated from an individual and first activated and stimulated to proliferate in vitro prior to being modified to express a multivalent CAR. 
     In order to achieve sufficient therapeutic doses of T cell compositions, T cells are often subjected to one or more rounds of stimulation, activation and/or expansion. T cells can 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; and 6,867,041, each of which is incorporated herein by reference in its entirety. In particular embodiments, T cells are activated and expanded for about 6 hours, about 12 hours, about 18 hours or about 24 hours prior to introduction of vectors or mRNAs encoding the multivalent CARs contemplated herein. 
     In one embodiment, T cells are activated at the same time that they are modified. 
     In various embodiments, a method of generating a CAR T cell comprises activating a population of cells comprising T cells and expanding the population of T cells. T cell activation can be accomplished by providing a primary stimulation signal through the T cell TCR/CD3 complex and by providing a secondary costimulation signal through an accessory molecule, e.g., CD28. 
     The TCR/CD3 complex may be stimulated by contacting the T cell with a suitable CD3 binding agent, e.g., a CD3 ligand or an anti-CD3 monoclonal antibody. Illustrative examples of CD3 antibodies include, but are not limited to, OKT3, G19-4, BC3, and 64.1. 
     In addition to the primary stimulation signal provided through the TCR/CD3 complex, induction of T cell responses requires a second, costimulatory signal. In particular embodiments, a CD28 binding agent can be used to provide a costimulatory signal. Illustrative examples of CD28 binding agents include but are not limited to: natural CD 28 ligands, e.g., a natural ligand for CD28 (e.g., a member of the B7 family of proteins, such as B7-1(CD80) and B7-2 (CD86); and anti-CD28 monoclonal antibody or fragment thereof capable of crosslinking the CD28 molecule, e.g., monoclonal antibodies 9.3, B-T3, XR-CD28, KOLT-2, 15E8, 248.23.2, and EX5.3D10. 
     In one embodiment, the molecule providing the primary stimulation signal, for example a molecule which provides stimulation through the TCR/CD3 complex and the costimulatory molecule are coupled to the same surface. 
     In certain embodiments, binding agents that provide stimulatory and costimulatory signals are localized on the surface of a cell. This can be accomplished by transfecting or transducing a cell with a nucleic acid encoding the binding agent in a form suitable for its expression on the cell surface or alternatively by coupling a binding agent to the cell surface. 
     In another embodiment, the molecule providing the primary stimulation signal, for example a molecule which provides stimulation through the TCR/CD3 complex and the costimulatory molecule are displayed on antigen presenting cells. 
     In one embodiment, the molecule providing the primary stimulation signal, for example a molecule which provides stimulation through the TCR/CD3 complex and the costimulatory molecule are provided on separate surfaces. 
     In a certain embodiment, one of the binding agents that provides stimulatory and costimulatory signals is soluble (provided in solution) and the other agent(s) is provided on one or more surfaces. 
     In a particular embodiment, the binding agents that provide stimulatory and costimulatory signals are both provided in a soluble form (provided in solution). 
     In various embodiments, the methods for making CAR T cells contemplated herein comprise activating T cells with anti-CD3 and anti-CD28 antibodies. 
     In one embodiment, expanding T cells activated by the methods contemplated herein further comprises culturing a population of cells comprising T cells for several hours (about 3 hours) to about 7 days to about 28 days or any hourly integer value in between. In another embodiment, the T cell composition may be cultured for 14 days. In a particular embodiment, T cells are cultured for about 21 days. In another embodiment, the T cell compositions are cultured for about 2-3 days. Several cycles of stimulation/activation/expansion may also be desired such that culture time of T cells can be 60 days or more. 
     In particular embodiments, conditions appropriate for T cell culture include an appropriate media (e.g., Minimal Essential Media or RPMI Media 1640 or, X-vivo 15, (Lonza)) and one or more factors necessary for proliferation and viability including, but not limited to serum (e.g., fetal bovine or human serum), interleukin-2 (IL-2), insulin, IFN-γ, IL-4, IL-7, IL-21, GM-CSF, IL-10, IL-12, IL-15, TGFβ, and TNF-α or any other additives suitable for the growth of cells known to the skilled artisan. 
     Further illustrative examples of cell culture media include, but are not limited to RPMI 1640, Clicks, AIM-V, DMEM, MEM, a-MEM, F-12, X-Vivo 15, and X-Vivo 20, Optimizer, with added amino acids, sodium pyruvate, and vitamins, either serum-free or supplemented with an appropriate amount of serum (or plasma) or a defined set of hormones, and/or an amount of cytokine(s) sufficient for the growth and expansion of T cells. 
     Antibiotics, e.g., penicillin and streptomycin, are included only in experimental cultures, not in cultures of cells that are to be infused into a subject. The target cells are maintained under conditions necessary to support growth, for example, an appropriate temperature (e.g., 37° C.) and atmosphere (e.g., air plus 5% C02). 
     In particular embodiments, PBMCs or isolated T cells are contacted with a stimulatory agent and costimulatory agent, such as anti-CD3 and anti-CD28 antibodies, generally attached to a bead or other surface, in a culture medium with appropriate cytokines, such as IL-2, IL-7, and/or IL-15. 
     In other embodiments, artificial APC (aAPC) made by engineering K562, U937, 721.221, T2, and C1R cells to direct the stable expression and secretion, of a variety of costimulatory molecules and cytokines. In a particular embodiment K32 or U32 aAPCs are used to direct the display of one or more antibody-based stimulatory molecules on the AAPC cell surface. Populations of T cells can be expanded by aAPCs expressing a variety of costimulatory molecules including, but not limited to, CD137L (4-1BBL), CD134L (OX40L), and/or CD80 or CD86. Finally, the aAPCs provide an efficient platform to expand genetically modified T cells and to maintain CD28 expression on CD8 T cells. aAPCs provided in WO 03/057171 and US2003/0147869 are hereby incorporated by reference in their entirety. 
     In a particular embodiment, polynucleotide encoding a CAR are introduced into the population of T cells. The polynucleotides may be introduced into the T cells by microinjection, transfection, lipofection, heat-shock, electroporation, transduction, gene gun, microinjection, DEAE-dextran-mediated transfer, and the like. 
     In various embodiments, a multivalent CAR T cell is generated. 
     In a preferred embodiment, polynucleotides are introduced into a T cell by viral transduction. 
     Illustrative examples of viral vector systems suitable for introducing a polynucleotide into an immune effector cell or CD34 +  cell include, but are not limited to adeno-associated virus (AAV), retrovirus, herpes simplex virus, adenovirus, vaccinia virus vectors for gene transfer. 
     In one embodiment, polynucleotides are introduced into a T cell by AAV transduction. 
     In one embodiment, polynucleotides are introduced into a T cell by retroviral transduction. 
     In one embodiment, polynucleotides are introduced into a T cell by lentiviral transduction. 
     In one embodiment, polynucleotides are introduced into a T cell by adenovirus transduction. 
     In one embodiment, polynucleotides are introduced into a T cell by herpes simplex virus transduction. 
     In one embodiment, polynucleotides are introduced into a T cell by vaccinia virus transduction. 
     In particular embodiments, methods of generating genetically modified T cells comprises contacting the cells with a stimulatory agent and costimulatory agent, such as soluble anti-CD3 and anti-CD28 antibodies, or antibodies attached to a bead or other surface, in a culture medium with appropriate cytokines, such as IL-2, IL-7, and/or IL-15 and/or one or more agents that modulate a PI3K cell signaling pathway. 
     As used herein, the term “PI3K inhibitor” refers to a nucleic acid, peptide, compound, or small organic molecule that binds to and inhibits at least one activity of PI3K. The PI3K proteins can be divided into three classes, class 1 PI3Ks, class 2 PI3Ks, and class 3 PI3Ks. Class 1 PI3Ks exist as heterodimers consisting of one of four p110 catalytic subunits (p110α, p110β, p110δ, and p110γ) and one of two families of regulatory subunits. In particular embodiments, a PI3K inhibitor targets the class 1 PI3K inhibitors. In one embodiment, a PI3K inhibitor will display selectivity for one or more isoforms of the class 1 PI3K inhibitors (i.e., selectivity for p110α, p110β, p110δ, and p110γ or one or more of p110α, p110β, p110δ, and p110γ). In another aspect, a PI3K inhibitor will not display isoform selectivity and be considered a “pan-PI3K inhibitor.” In one embodiment, a PI3K inhibitor will compete for binding with ATP to the PI3K catalytic domain. 
     Illustrative examples of PI3K inhibitors suitable for use particular embodiments include, but are not limited to, BKM120 (class 1 PI3K inhibitor, Novartis), XL147 (class 1 PI3K inhibitor, Exelixis), (pan-PI3K inhibitor, GlaxoSmithKline), and PX-866 (class 1 PI3K inhibitor; p110α, p110β, and p110γ isoforms, Oncothyreon). 
     Other illustrative examples of selective PI3K inhibitors include, but are not limited to BYL719, GSK2636771, TGX-221, AS25242, CAL-101, ZSTK474, and IPI-145. 
     Further illustrative examples of pan-PI3K inhibitors include, but are not limited to BEZ235, LY294002, GSK1059615, TG100713, and GDC-0941. 
     In a preferred embodiment, the PI3K inhibitor is ZSTK474. 
     G. Compositions and Formulations 
     The compositions contemplated herein may comprise one or more polypeptides, polynucleotides, vectors comprising same, genetically modified immune effector cells, etc. Compositions include, but are not limited to pharmaceutical compositions. A “pharmaceutical composition” refers to a composition formulated in pharmaceutically-acceptable or physiologically-acceptable solutions for administration to a cell or an animal, either alone, or in combination with one or more other modalities of therapy. It will also be understood that, if desired, the compositions may be administered in combination with other agents as well, such as, e.g., cytokines, growth factors, hormones, small molecules, chemotherapeutics, pro-drugs, drugs, antibodies, or other various pharmaceutically-active agents. There is virtually no limit to other components that may also be included in the compositions, provided that the additional agents do not adversely affect the ability of the composition to deliver the intended therapy. 
     The phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. 
     As used herein “pharmaceutically acceptable carrier” includes without limitation any adjuvant, carrier, excipient, glidant, sweetening agent, diluent, preservative, dye/colorant, flavor enhancer, surfactant, wetting agent, dispersing agent, suspending agent, stabilizer, isotonic agent, solvent, surfactant, or emulsifier which has been approved by the United States Food and Drug Administration as being acceptable for use in humans or domestic animals. Exemplary pharmaceutically acceptable carriers include, but are not limited to, to sugars, such as lactose, glucose and sucrose; starches, such as corn starch and potato starch; cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; tragacanth; malt; gelatin; talc; cocoa butter, waxes, animal and vegetable fats, paraffins, silicones, bentonites, silicic acid, zinc oxide; oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; glycols, such as propylene glycol; polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; esters, such as ethyl oleate and ethyl laurate; agar; buffering agents, such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer&#39;s solution; ethyl alcohol; phosphate buffer solutions; and any other compatible substances employed in pharmaceutical formulations. 
     In particular embodiments, compositions comprise an amount of multivalent CAR-expressing immune effector cells contemplated herein. 
     As used herein, the term “amount” refers to “an amount effective” or “an effective amount” of a therapeutic cell, a multivalent CAR T cell etc., to achieve a beneficial or desired prophylactic or therapeutic result, including clinical results. 
     A “prophylactically effective amount” refers to an amount of a therapeutic cell, a multivalent CAR T cell, etc., effective to achieve the desired prophylactic result. Typically but not necessarily, since a prophylactic dose is used in subjects prior to or at an earlier stage of disease, the prophylactically effective amount is less than the therapeutically effective amount. 
     A “therapeutically effective amount” of a therapeutic cell, a multivalent CAR T cell, etc., may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the composition to elicit a desired response in the individual. A therapeutically effective amount is also one in which any toxic or detrimental effects of a therapeutic cell, a multivalent CAR T cell, etc., are outweighed by the therapeutically beneficial effects. The term “therapeutically effective amount” includes an amount that is effective to “treat” a subject (e.g., a patient). When a therapeutic amount is indicated, the precise amount of the compositions 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 2  to 10 10  cells/kg body weight, preferably 10 5  to 10 6  cells/kg body weight, including all integer values within those ranges. The number of cells will depend upon the ultimate use for which the composition is intended as will the type of cells included therein. For uses provided herein, the cells are generally in a volume of a liter or less, can be 500 mLs or less, even 250 mLs or 100 mLs or less. Hence the density of the desired cells is typically greater than 10 6  cells/ml and generally is greater than 10′ cells/ml, generally 10 8  cells/ml or greater. The clinically relevant number of immune cells can be apportioned into multiple infusions that cumulatively equal or exceed 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , or 10 12  cells. In some embodiments, particularly since all the infused cells will be redirected to a particular target antigen, lower numbers of cells, in the range of 10 6 /kilogram (10 6 -10 11  per patient) may be administered. T cell compositions that comprise T cells that express multivalent CARs may be administered multiple times at dosages within these ranges. The cells may be allogeneic, syngeneic, xenogeneic, or autologous to the patient undergoing therapy. If desired, the treatment may also include administration of mitogens (e.g., PHA) or lymphokines, cytokines, and/or chemokines (e.g., IFN-γ, IL-2, IL-12, TNF-alpha, IL-18, and TNF-beta, GM-CSF, IL-4, IL-13, Flt3-L, RANTES, MIP1α, etc.) as described herein to enhance induction of the immune response. 
     Generally, compositions comprising the cells activated and expanded as described herein may be utilized in the treatment and prevention of diseases that arise in individuals who are immunocompromised. In particular, compositions contemplated herein are used in the treatment of cancer. In particular embodiments, multivalent CAR-modified T cells may be administered either alone, or as a pharmaceutical composition in combination with carriers, diluents, excipients, and/or with other components such as IL-2 or other cytokines or cell populations. 
     In particular embodiments, pharmaceutical compositions comprise an amount of genetically modified T cells, in combination with one or more pharmaceutically or physiologically acceptable carriers, diluents or excipients. 
     Pharmaceutical compositions comprising a multivalent CAR-expressing immune effector cell population, such as T cells, 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. In particular embodiments, compositions are preferably formulated for nasal, oral, enteral, or parenteral administration, e.g., intravascular (intravenous or intraarterial), intraperitoneal or intramuscular administration. 
     The liquid pharmaceutical compositions, whether they be solutions, suspensions or other like form, may include one or more of the following: sterile diluents such as water for injection, saline solution, preferably physiological saline, Ringer&#39;s solution, isotonic sodium chloride, fixed oils such as synthetic mono or diglycerides which may serve as the solvent or suspending medium, polyethylene glycols, glycerin, propylene glycol or other solvents; antibacterial agents such as benzyl alcohol or methyl paraben; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. An injectable pharmaceutical composition is preferably sterile. 
     In one embodiment, the T cell compositions contemplated herein are formulated in a pharmaceutically acceptable cell culture medium. Such compositions are suitable for administration to human subjects. In particular embodiments, the pharmaceutically acceptable cell culture medium is a serum free medium. 
     Serum-free medium has several advantages over serum containing medium, including a simplified and better defined composition, a reduced degree of contaminants, elimination of a potential source of infectious agents, and lower cost. In various embodiments, the serum-free medium is animal-free, and may optionally be protein-free. Optionally, the medium may contain biopharmaceutically acceptable recombinant proteins. “Animal-free” medium refers to medium wherein the components are derived from non-animal sources. Recombinant proteins replace native animal proteins in animal-free medium and the nutrients are obtained from synthetic, plant or microbial sources. “Protein-free” medium, in contrast, is defined as substantially free of protein. 
     Illustrative examples of serum-free media used in particular compositions includes but is not limited to QBSF-60 (Quality Biological, Inc.), StemPro-34 (Life Technologies), and X-VIVO 10. 
     In one preferred embodiment, compositions comprising T cells contemplated herein are formulated in a solution comprising PlasmaLyte A. 
     In another preferred embodiment, compositions comprising T cells contemplated herein are formulated in a solution comprising a cryopreservation medium. For example, cryopreservation media with cryopreservation agents may be used to maintain a high cell viability outcome post-thaw. Illustrative examples of cryopreservation media used in particular compositions includes, but is not limited to, CryoStor CS10, CryoStor CSS, and CryoStor CS2. 
     In a more preferred embodiment, compositions comprising T cells contemplated herein are formulated in a solution comprising 50:50 PlasmaLyte A to CryoStor CS10. 
     In a particular embodiment, compositions comprise an effective amount of multivalent CAR-expressing immune effector cells, alone or in combination with one or more therapeutic agents. Thus, the multivalent CAR-expressing immune effector cell compositions may be administered alone or in combination with other known cancer treatments, such as radiation therapy, chemotherapy, transplantation, immunotherapy, hormone therapy, photodynamic therapy, etc. The compositions may also be administered in combination with antibiotics. Such therapeutic agents may be accepted in the art as a standard treatment for a particular disease state as described herein, such as a particular cancer. Exemplary therapeutic agents contemplated include cytokines, growth factors, steroids, NSAIDs, DMARDs, anti-inflammatories, chemotherapeutics, radiotherapeutics, therapeutic antibodies, or other active and ancillary agents. 
     In certain embodiments, compositions comprising multivalent CAR-expressing immune effector cells disclosed herein may be administered in conjunction with any number of chemotherapeutic agents. Illustrative examples of chemotherapeutic agents include alkylating agents such as thiotepa and cyclophosphamide (CYTOXAN™); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, trietylenephosphoramide, triethylenethiophosphaoramide and trimethylolomelamine resume; nitrogen mustards such as chlorambucil, chlornaphazine, cholophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, ranimustine; antibiotics such as aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, calicheamicin, carabicin, carminomycin, carzinophilin, chromomycins, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, doxorubicin, epirubicin, esorubicin, idarubicin, marcellomycin, mitomycins, mycophenolic acid, nogalamycin, olivomycins, peplomycin, potfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogues such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine, 5-FU; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elformithine; elliptinium acetate; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidamine; mitoguazone; mitoxantrone; mopidamol; nitracrine; pentostatin; phenamet; pirarubicin; podophyllinic acid; 2-ethylhydrazide; procarbazine; PSK®; razoxane; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2, 2′,2″-trichlorotriethylamine; urethan; vindesine; dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (“Ara-C”); cyclophosphamide; thiotepa; taxoids, e.g. paclitaxel (TAXOL®, Bristol-Myers Squibb Oncology, Princeton, N.J.) and doxetaxel (TAXOTERE®., Rhne-Poulenc Rorer, Antony, France); chlorambucil; gemcitabine; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine; platinum; etoposide (VP-16); ifosfamide; mitomycin C; mitoxantrone; vincristine; vinorelbine; navelbine; novantrone; teniposide; daunomycin; aminopterin; xeloda; ibandronate; CPT-11; topoisomerase inhibitor RFS 2000; difluoromethylomithine (DMFO); retinoic acid derivatives such as Targretin™ (bexarotene), Panretin™ (alitretinoin) ; ONTAK™ (denileukin diftitox); esperamicins; capecitabine; and pharmaceutically acceptable salts, acids or derivatives of any of the above. Also included in this definition are anti-hormonal agents that act to regulate or inhibit hormone action on cancers such as anti-estrogens including for example tamoxifen, raloxifene, aromatase inhibiting 4(5)-imidazoles, 4-hydroxytamoxifen, trioxifene, keoxifene, LY117018, onapristone, and toremifene (Fareston); and anti-androgens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin; and pharmaceutically acceptable salts, acids or derivatives of any of the above. 
     A variety of other therapeutic agents may be used in conjunction with the compositions described herein. In one embodiment, the composition comprising multivalent CAR-expressing immune effector cells is administered with an anti-inflammatory agent. Anti-inflammatory agents or drugs include, but are not limited to, steroids and glucocorticoids (including betamethasone, budesonide, dexamethasone, hydrocortisone acetate, hydrocortisone, hydrocortisone, methylprednisolone, prednisolone, prednisone, triamcinolone), nonsteroidal anti-inflammatory drugs (NSAIDS) including aspirin, ibuprofen, naproxen, methotrexate, sulfasalazine, leflunomide, anti-TNF medications, cyclophosphamide and mycophenolate. 
     Other exemplary NSAIDs are chosen from the group consisting of ibuprofen, naproxen, naproxen sodium, Cox-2 inhibitors such as VIOXX® (rofecoxib) and CELEBREX® (celecoxib), and sialylates. Exemplary analgesics are chosen from the group consisting of acetaminophen, oxycodone, tramadol of proporxyphene hydrochloride. Exemplary glucocorticoids are chosen from the group consisting of cortisone, dexamethasone, hydrocortisone, methylprednisolone, prednisolone, or prednisone. Exemplary biological response modifiers include molecules directed against cell surface markers (e.g., CD4, CD5, etc.), cytokine inhibitors, such as the TNF antagonists (e.g., etanercept (ENBREL®), adalimumab (HUMIRA®) and infliximab (REMICADE®), chemokine inhibitors and adhesion molecule inhibitors. The biological response modifiers include monoclonal antibodies as well as recombinant forms of molecules. Exemplary DMARDs include azathioprine, cyclophosphamide, cyclosporine, methotrexate, penicillamine, leflunomide, sulfasalazine, hydroxychloroquine, Gold (oral (auranofin) and intramuscular) and minocycline. 
     Illustrative examples of therapeutic antibodies suitable for combination with the multivalent CAR modified T cells contemplated herein, include but are not limited to, bavituximab, bevacizumab (avastin), bivatuzumab, blinatumomab, conatumumab, daratumumab, duligotumab, dacetuzumab, dalotuzumab, elotuzumab (HuLuc63), gemtuzumab, ibritumomab, indatuximab, inotuzumab, lorvotuzumab, lucatumumab, milatuzumab, moxetumomab, ocaratuzumab, ofatumumab, rituximab, siltuximab, teprotumumab, and ublituximab. 
     In certain embodiments, the compositions described herein are administered in conjunction with a cytokine. By “cytokine” as used herein is meant a generic term for proteins released by one cell population that act on another cell as intercellular mediators. Examples of such cytokines are lymphokines, monokines, and traditional polypeptide hormones. Included among the cytokines are growth hormones such as human growth hormone, N-methionyl human growth hormone, and bovine growth hormone; parathyroid hormone; thyroxine; insulin; proinsulin; relaxin; prorelaxin; glycoprotein hormones such as follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), and luteinizing hormone (LH); hepatic growth factor; fibroblast growth factor; prolactin; placental lactogen; tumor necrosis factor-alpha and -beta; mullerian-inhibiting substance; mouse gonadotropin-associated peptide; inhibin; activin; vascular endothelial growth factor; integrin; thrombopoietin (TPO); nerve growth factors such as NGF-beta; platelet-growth factor; transforming growth factors (TGFs) such as TGF-alpha and TGF-beta; insulin-like growth factor-I and -II; erythropoietin (EPO); osteoinductive factors; interferons such as interferon-alpha, beta, and -gamma; colony stimulating factors (CSFs) such as macrophage-CSF (M-CSF); granulocyte-macrophage-CSF (GM-CSF); and granulocyte-CSF (G-CSF); interleukins (ILs) such as IL-1, IL-1 alpha, IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-11, IL-12; IL-15, a tumor necrosis factor such as TNF-alpha or TNF-beta; and other polypeptide factors including LIF and kit ligand (KL). As used herein, the term cytokine includes proteins from natural sources or from recombinant cell culture, and biologically active equivalents of the native sequence cytokines. 
     H. Therapeutic Methods 
     The multivalent CAR immune effector cells contemplated herein provide improved methods of adoptive immunotherapy for use in the prevention, treatment, and amelioration immune disorders, or for preventing, treating, or ameliorating at least one symptom associated with an immune disorder. In preferred embodiments, the multivalent CAR immune effector cells contemplated herein provide improved methods of adoptive immunotherapy for use in the prevent, treatment, and amelioration of at least one symptom associated with cancer. 
     An “immune disorder” refers to a disease that evokes a response from the immune system. In particular embodiments, the term “immune disorder” refers to a cancer, graft-versus-host disease, an autoimmune disease, or an immunodeficiency. In one embodiment, immune disorders encompass infectious disease. 
     As used herein, the term “cancer” relates generally to a class of diseases or conditions in which abnormal cells divide without control and can invade nearby tissues. 
     As used herein, the term “malignant” refers to a cancer in which a group of tumor cells display one or more of uncontrolled growth (i.e., division beyond normal limits), invasion (i.e., intrusion on and destruction of adjacent tissues), and metastasis (i.e., spread to other locations in the body via lymph or blood). 
     As used herein, the term “metastasize” refers to the spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. 
     As used herein, the term “benign” or “non-malignant” refers to tumors that may grow larger but do not spread to other parts of the body. Benign tumors are self-limited and typically do not invade or metastasize. 
     A “cancer cell” or “tumor cell” refers to an individual cell of a cancerous growth or tissue. A tumor refers generally to a swelling or lesion formed by an abnormal growth of cells, which may be benign, pre-malignant, or malignant. Most cancers form tumors, but some, e.g., leukemia, do not necessarily form tumors. For those cancers that form tumors, the terms cancer (cell) and tumor (cell) are used interchangeably. The amount of a tumor in an individual is the “tumor burden” which can be measured as the number, volume, or weight of the tumor. 
     “Graft-versus-host disease” or “GVHD” refers complications that can occur after cell, tissue, or solid organ transplant. GVHD can occur after a stem cell or bone marrow transplant in which the transplanted donor cells attack the transplant recipient&#39;s body. Acute GVHD in humans takes place within about 60 days post-transplantation and results in damage to the skin, liver, and gut by the action of cytolytic lymphocytes. Chronic GVHD occurs later and is a systemic autoimmune disease that affects primarily the skin, resulting in the polyclonal activation of B cells and the hyperproduction of Ig and autoantibodies. Solid-organ transplant graft-versus-host disease (SOT-GVHD) occurs in two forms. The more common type is antibody mediated, wherein antibodies from a donor with blood type 0 attack a recipient&#39;s red blood cells in recipients with blood type A, B, or AB, leading to mild transient, hemolytic anemias. The second form of SOT-GVHD is a cellular type associated with high mortality, wherein donor-derived T cells produce an immunological attack against immunologically disparate host tissue, most often in the skin, liver, gastrointestinal tract, and bone marrow, leading to complications in these organs. 
     “Graft-versus-leukemia” or “GVL” refer to an immune response to a person&#39;s leukemia cells by immune cells present in a donor&#39;s transplanted tissue, such as bone marrow or peripheral blood. 
     An “autoimmune disease” refers to a disease in which the body produces an immunogenic (i.e., immune system) response to some constituent of its own tissue. In other words, the immune system loses its ability to recognize some tissue or system within the body as “self” and targets and attacks it as if it were foreign. Illustrative examples of autoimmune diseases include, but are not limited to: arthritis, inflammatory bowel disease, Hashimoto&#39;s thyroiditis, Grave&#39;s disease, lupus, multiple sclerosis, rheumatic arthritis, hemolytic anemia, anti-immune thyroiditis, systemic lupus erythematosus, celiac disease, Crohn&#39;s disease, colitis, diabetes, scleroderma, psoriasis, and the like. 
     An “immunodeficiency” means the state of a patient whose immune system has been compromised by disease or by administration of chemicals. This condition makes the system deficient in the number and type of blood cells needed to defend against a foreign substance. Immunodeficiency conditions or diseases are known in the art and include, for example, AIDS (acquired immunodeficiency syndrome), SCID (severe combined immunodeficiency disease), selective IgA deficiency, common variable immunodeficiency, X-linked agammaglobulinemia, chronic granulomatous disease, hyper-IgM syndrome, Wiskott-Aldrich Syndrome (WAS), and diabetes. 
     An “infectious disease” refers to a disease that can be transmitted from person to person or from organism to organism, and is caused by a microbial or viral agent (e.g., common cold). Infectious diseases are known in the art and include, for example, hepatitis, sexually transmitted diseases (e.g., Chlamydia, gonorrhea), tuberculosis, HIV/AIDS, diphtheria, hepatitis B, hepatitis C, cholera, and influenza. 
     As used herein, the terms “individual” and “subject” are often used interchangeably and refer to any animal that exhibits a symptom of an immune disorder that can be treated with the multivalent CARs, immune effector cells expressing the same, and methods contemplated elsewhere herein. Suitable subjects (e.g., patients) include laboratory animals (such as mouse, rat, rabbit, or guinea pig), farm animals, and domestic animals or pets (such as a cat or dog). Non-human primates and, preferably, human subjects, are included. Typical subjects include human patients that have, have been diagnosed with, or are at risk of having an immune disorder. 
     As used herein, the term “patient” refers to a subject that has been diagnosed with an immune disorder that can be treated with the multivalent CARs, immune effector cells expressing the same, and methods contemplated elsewhere herein. 
     As used herein “treatment” or “treating,” includes any beneficial or desirable effect on the symptoms or pathology of a disease or pathological condition, and may include even minimal reductions in one or more measurable markers of the disease or condition being treated, e.g., cancer, GVHD, infectious disease, autoimmune disease, inflammatory disease, and immunodeficiency. Treatment can optionally involve delaying of the progression of the disease or condition. “Treatment” does not necessarily indicate complete eradication or cure of the disease or condition, or associated symptoms thereof. 
     As used herein, “prevent,” and similar words such as “prevention,” “prevented,” “preventing” etc., indicate an approach for preventing, inhibiting, or reducing the likelihood of the occurrence or recurrence of, a disease or condition, e.g., cancer, GVHD, infectious disease, autoimmune disease, inflammatory disease, and immunodeficiency. It also refers to delaying the onset or recurrence of a disease or condition or delaying the occurrence or recurrence of the symptoms of a disease or condition. As used herein, “prevention” and similar words also includes reducing the intensity, effect, symptoms and/or burden of a disease or condition prior to onset or recurrence of the disease or condition. 
     As used herein, the phrase “ameliorating at least one symptom of” refers to decreasing one or more symptoms of the disease or condition for which the subject is being treated, e.g., cancer, GVHD, infectious disease, autoimmune disease, inflammatory disease, and immunodeficiency. In particular embodiments, the disease or condition being treated is a cancer, wherein the one or more symptoms ameliorated include, but are not limited to, weakness, fatigue, shortness of breath, easy bruising and bleeding, frequent infections, enlarged lymph nodes, distended or painful abdomen (due to enlarged abdominal organs), bone or joint pain, fractures, unplanned weight loss, poor appetite, night sweats, persistent mild fever, and decreased urination (due to impaired kidney function). 
     In various embodiments, the multivalent CAR T cells contemplated herein provide improved methods of adoptive immunotherapy for use in increasing the cytotoxicity toward cancer cells or for use in decreasing the number of relapsed or refractory cancer cells. 
     In particular embodiments, the specificity of a primary T cell is redirected to tumor or cancer cells by genetically modifying the primary T cell with a multivalent CAR directed to first and/or second antigens expressed on the cancer cells. In one embodiment, the multivalent CAR T cells are infused to a recipient in need thereof. The infused cells are able to kill tumor cells in the recipient. Unlike antibody therapies, multivalent CAR T cells are able to replicate in vivo; thus, contributing to long-term persistence that can lead to a more sustained cancer therapy. 
     In one embodiment, multivalent CAR T cells are administered to a subject diagnosed with cancer. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of solid tumors or cancers. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of solid tumors or cancers including, but not limited to: adrenal cancer, adrenocortical carcinoma, anal cancer, appendix cancer, astrocytoma, atypical teratoid/rhabdoid tumor, basal cell carcinoma, bile duct cancer, bladder cancer, bone cancer, brain/CNS cancer, breast cancer, bronchial tumors, cardiac tumors, cervical cancer, cholangiocarcinoma, chondrosarcoma, chordoma, colon cancer, colorectal cancer, craniopharyngioma, ductal carcinoma in situ (DCIS) endometrial cancer, ependymoma, esophageal cancer, esthesioneuroblastoma, Ewing&#39;s sarcoma, extracranial germ cell tumor, extragonadal germ cell tumor, eye cancer, fallopian tube cancer, fibrous histiosarcoma, fibrosarcoma, gallbladder cancer, gastric cancer, gastrointestinal carcinoid tumors, gastrointestinal stromal tumor (GIST), germ cell tumors, glioma, glioblastoma, head and neck cancer, hemangioblastoma, hepatocellular cancer, hypopharyngeal cancer, intraocular melanoma, kaposi sarcoma, kidney cancer, laryngeal cancer, leiomyosarcoma, lip cancer, liposarcoma, liver cancer, lung cancer, non-small cell lung cancer, lung carcinoid tumor, malignant mesothelioma, medullary carcinoma, medulloblastoma, menangioma, melanoma, Merkel cell carcinoma, midline tract carcinoma, mouth cancer, myxosarcoma, myelodysplastic syndrome, myeloproliferative neoplasms, nasal cavity and paranasal sinus cancer, nasopharyngeal cancer, neuroblastoma, oligodendroglioma, oral cancer, oral cavity cancer, oropharyngeal cancer, osteosarcoma, ovarian cancer, pancreatic cancer, pancreatic islet cell tumors, papillary carcinoma, paraganglioma, parathyroid cancer, penile cancer, pharyngeal cancer, pheochromocytoma, pinealoma, pituitary tumor, pleuropulmonary blastoma, primary peritoneal cancer, prostate cancer, rectal cancer, retinoblastoma, renal cell carcinoma, renal pelvis and ureter cancer, rhabdomyosarcoma, salivary gland cancer, sebaceous gland carcinoma, skin cancer, soft tissue sarcoma, squamous cell carcinoma, small cell lung cancer, small intestine cancer, stomach cancer, sweat gland carcinoma, synovioma, testicular cancer, throat cancer, thymus cancer, thyroid cancer, urethral cancer, uterine cancer, uterine sarcoma, vaginal cancer, vascular cancer, vulvar cancer, and Wilms Tumor. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of solid tumors or cancers including, without limitation, liver cancer, pancreatic cancer, lung cancer, breast cancer, bladder cancer, brain cancer, bone cancer, thyroid cancer, kidney cancer, or skin cancer. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of various cancers including but not limited to pancreatic, bladder, and lung. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of liquid cancers or hematological cancers. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of B-cell malignancies, including but not limited to: leukemias, lymphomas, and multiple myeloma. 
     In particular embodiments, multivalent CAR T cells contemplated herein are used in the treatment of liquid cancers including, but not limited to leukemias, lymphomas, and multiple myelomas: acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), myeloblastic, promyelocytic, myelomonocytic, monocytic, erythroleukemia, hairy cell leukemia (HCL), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CIVIL), chronic myelomonocytic leukemia (CMML) and polycythemia vera, Hodgkin lymphoma, nodular lymphocyte-predominant Hodgkin lymphoma, Burkitt lymphoma, small lymphocytic lymphoma (SLL), diffuse large B-cell lymphoma, follicular lymphoma, immunoblastic large cell lymphoma, precursor B-lymphoblastic lymphoma, mantle cell lymphoma, marginal zone lymphoma, mycosis fungoides, anaplastic large cell lymphoma, Sézary syndrome, precursor T-lymphoblastic lymphoma, multiple myeloma, overt multiple myeloma, smoldering multiple myeloma, plasma cell leukemia, non-secretory myeloma, IgD myeloma, osteosclerotic myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma. 
     In particular embodiments, a method comprises administering a therapeutically effective amount of multivalent CAR T cells, to a patient in need thereof. 
     In certain embodiments, the cells are used in the treatment of patients at risk for developing a cancer. Thus, particular embodiments comprise the treatment or prevention or amelioration of at least one symptom of a cancer comprising administering to a patient in need thereof, a therapeutically effective amount of multivalent CAR T cells. 
     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 amount of immune effector cells, e.g., T cells, in the composition administered to a subject is at least 0.1×10 5  cells, at least 0.5×10 5  cells, at least 1×10 5  cells, at least 5×10 5  cells, at least 1×10 6  cells, at least 0.5×10 7  cells, at least 1×10 7  cells, at least 0.5×10 8  cells, at least 1×10 8  cells, at least 0.5 x 10 9  cells, at least 1×10 9  cells, at least 2×10 9  cells, at least 3×10 9  cells, at least 4×10 9  cells, at least 5×10 9  cells, or at least 1×10 10  cells. 
     In particular embodiments, about 1×10 7  T cells to about 1×10 9  T cells, about 2×10 7  T cells to about 0.9×10 9  T cells, about 3×10 7  T cells to about 0.8×10 9  T cells, about 4×10 7  T cells to about 0.7×10 9  T cells, about 5×10 7  T cells to about 0.6×10 9  T cells, or about 5×10 7  T cells to about 0.5×10 9  T cells are administered to a subject. 
     In one embodiment, the amount of immune effector cells, e.g., T cells, in the composition administered to a subject is at least 0.1×10 4  cells/kg of bodyweight, at least 0.5×10 4  cells/kg of bodyweight, at least 1×10 4  cells/kg of bodyweight, at least 5×10 4  cells/kg of bodyweight, at least 1×10 5  cells/kg of bodyweight, at least 0.5×10 6  cells/kg of bodyweight, at least 1×10 6  cells/kg of bodyweight, at least 0.5×10 7  cells/kg of bodyweight, at least 1×10 7  cells/kg of bodyweight, at least 0.5×10 8  cells/kg of bodyweight, at least 1×10 8  cells/kg of bodyweight, at least 2×10 8  cells/kg of bodyweight, at least 3×10 8  cells/kg of bodyweight, at least 4×10 8  cells/kg of bodyweight, at least 5×10 8  cells/kg of bodyweight, or at least 1×10 9  cells/kg of bodyweight. 
     In particular embodiments, about 1×10 6  T cells/kg of bodyweight to about 1×10 8  T cells/kg of bodyweight, about 2×10 6  T cells/kg of bodyweight to about 0.9×10 8  T cells/kg of bodyweight, about 3×10 6  T cells/kg of bodyweight to about 0.8×10 8  T cells/kg of bodyweight, about 4×10 6  T cells/kg of bodyweight to about 0.7×10 8  T cells/kg of bodyweight, about 5×10 6  T cells/kg of bodyweight to about 0.6×10 8  T cells/kg of bodyweight, or about 5×10 6  T cells/kg of bodyweight to about 0.5×10 8  T cells/kg of bodyweight are administered to a subject. 
     One of ordinary skill in the art would recognize that multiple administrations of the compositions contemplated in particular embodiments may be required to effect the desired therapy. For example, a composition may be administered 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more times over a span of 1 week, 2 weeks, 3 weeks, 1 month, 2 months, 3 months, 4 months, 5 months, 6 months, 1 year, 2 years, 5, years, 10 years, or more. 
     In certain embodiments, it may be desirable to administer activated T cells to a subject and then subsequently redraw blood (or have an apheresis performed), activate T cells therefrom, and reinfuse the patient with these activated and expanded T cells. This process can be carried out multiple times every few weeks. In certain embodiments, T cells can be activated from blood draws of from 10 cc to 400 cc. In certain embodiments, T cells are activated from blood draws of 20 cc, 30 cc, 40 cc, 50 cc, 60 cc, 70 cc, 80 cc, 90 cc, 100cc, 150cc, 200cc, 250cc, 300cc, 350cc, or 400 cc or more. Not to be bound by theory, using this multiple blood draw/multiple reinfusion protocol may serve to select out certain populations of T cells. 
     The administration of the compositions contemplated in particular embodiments may be carried out in any convenient manner, including by aerosol inhalation, injection, ingestion, transfusion, implantation or transplantation. In a preferred embodiment, compositions are administered nasally, orally, enterally, or parenterally. The phrases “parenteral administration” and “administered parenterally” as used herein refers to modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravascular, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intratumoral, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid, intraspinal and intrasternal injection and infusion. In one embodiment, the compositions contemplated herein are administered to a subject by direct injection into a tumor, lymph node, or site of infection. 
     In one embodiment, a subject in need thereof is administered an effective amount of a composition to increase a cellular immune response to a cancer in the subject. The immune response may include cellular immune responses mediated by cytotoxic T cells capable of killing infected cells, regulatory T cells, and helper T cell responses. Humoral immune responses, mediated primarily by helper T cells capable of activating B cells thus leading to antibody production, may also be induced. A variety of techniques may be used for analyzing the type of immune responses induced by the compositions, which are well described in the art; e.g., Current Protocols in Immunology, Edited by: John E. Coligan, Ada M. Kruisbeek, David H. Margulies, Ethan M. Shevach, Warren Strober (2001) John Wiley &amp; Sons, NY, N.Y. 
     In one embodiment, a method of treating a subject diagnosed with a cancer, comprises removing immune effector cells from the subject, modifying the immune effector cells to express a multivalent CAR contemplated herein and producing a population of modified immune effector cells, and administering the population of modified immune effector cells to the same subject. In a preferred embodiment, the immune effector cells comprise T cells. 
     The methods for administering the cell compositions contemplated in particular embodiments include any method which is effective to result in reintroduction of ex vivo modified immune effector cells or on reintroduction of the progenitors of immune effector cells that on introduction into a subject differentiate into mature immune effector cells. One method comprises modifying peripheral blood T cells ex vivo and returning the modified cells into the subject. 
     All publications, patent applications, and issued patents cited in this specification are herein incorporated by reference as if each individual publication, patent application, or issued patent were specifically and individually indicated to be incorporated by reference. 
     Although the foregoing embodiments have been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be readily apparent to one of ordinary skill in the art in light of the teachings contemplated herein that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims. The following examples are provided by way of illustration only and not by way of limitation. Those of skill in the art will readily recognize a variety of noncritical parameters that could be changed or modified to yield essentially similar results. 
     EXAMPLES 
     Example 1 
     Car Multiplexing in a Multivalent Format 
     Traditional CARs achieve antigen targeting using scFv domains composed of two chains, one from the variable heavy chain and the other from the variable light chain of antibodies. Camelids, and some cartilaginous fishes, naturally develop heavy chain only antibodies called V H H (camelids) or IgNAR (cartilaginous fish). The antigen binding region of these antibodies is commonly referred to as a single domain antibody fragment (sdAb), and is composed of a single monomeric variable antibody domain ( FIG. 1 ). Single domain antibody fragments are highly modular, stable, and approximately half the size of a scFv and are capable of binding selectively to specific antigens with high affinity. 
     The compact modularity of sdAb makes it an ideal candidate for CAR multiplexing in an in-line multivalent format ( FIG. 2  and  FIG. 3 ). 
     Multivalent CAR constructs were designed by fusing the sdAb clone 7D12 targeting EGFR (see, e.g., SEQ ID: 1-5), to the N-terminus of an anti-BCMA scFv CAR (see, e.g., SEQ ID: 6,7) using a (Gly 4 Ser) 3  linker (see, e.g., SEQ ID: 8-10).  FIG. 3 . 
     Monovalent and multivalent CARs were packaged into lentiviral particles used to transduce primary human peripheral blood mononuclear cells (PBMCs) in vitro. Transduced human PBMCs were assessed for CAR expression by labeling with fluorescent antigen and analyzed by flow cytometry.  FIG. 4A . Only the multivalent CAR construct were labeled with both antigens in an approximately equal amount indicating that both antigen binding domains were properly folded and retained antigen binding activity in a multivalent format. 
     Transduced cells were subsequently co-cultured with antigen positive A549 (BCMA+ and EGFR+) tumor cells at an E:T of 1:1 and cytotoxicity was monitored over time using an IncuCyte S3. After 48 hours of co-culture cytotoxicity of the A549 tumor cells was calculated from the area under the curve of co-cultured cells vs. tumor alone. The multivalent CAR construct demonstrated robust cytotoxicity compared to sdAb CAR or scFv CAR alone.  FIG. 4B . 
     Cytokine secretion from transduced cells co-cultured with A549 tumor cells at an E:T ratio of 1:1 was evaluated at 24 hours using the Intellicyt MultiCyt Qbeads Plexscreen secreted protein assay kit. IFNy was detected for the multivalent construct in response to both antigens ( FIG. 4C ). 
     Example 2 
     CD19-CD20 Tandem Cars 
     Tandem CARs were constructed by fusing single domain V H H antibodies to the N-terminus of scFv containing CAR. An anti-CD19 V H H (SEQ ID NO: 18) was fused to the N-terminus of an anti-CD20 scFv CAR (SEQ ID NO: 12) to generate an anti-CD19 V H H-anti-CD20 scFv tandem CAR (SEQ ID NO: 22). An anti-CD20 V H H (SEQ ID NO: 20) was fused to the N-terminus of an anti-CD19 scFv CAR (SEQ ID NO: 16) to generate an anti-CD20V H H-anti-CD19 scFv tandem CAR (SEQ ID NO: 24). In addition, the anti-CD19 V H H and the anti-CD20 V H H were formatted as a tandem CAR (SEQ ID NO: 26). 
     Monovalent and tandem CAR constructs were packaged into lentiviral particles used to transduce human PBMCs in vitro. Transduced human T cells were assessed for monovalent or tandem CAR expression by labeling with fluorescent antigen. In the case of CD20, no soluble fluorescent antigen was available so V H H expression was assessed with an anti-V H H antibody.  FIG. 7A . Only tandem constructs labeled with both CD19 and anti-VHH reagents. Id. 
     Transduced T cells were subsequently co-cultured with antigen positive A549 tumor cells at an effector: tumor ratio (E:T) of 1:1 and cytotoxicity was monitored over time using an Incucyte S3. After 48 h of tumor co-culture, cytotoxicity was calculated from the area under the curve of co-cultured cells vs. tumor alone. Tandem constructs were observed to have cytolytic activity against tumors expressing both antigens whereas monovalent constructs exhibited killing against only tumor cells positive for their respective antigens.  FIG. 7B . 
     Cytokine secretion from the transduced T cells was evaluated at 24 h using the Intellicyt MultiCyt QBeads Plexscreen secreted assay kit. As observed in the cytotoxicity assay, the results of the cytokine release assay confirmed that tandem CARs were capable of responding to tumor bearing both antigens but monovalent CARs only reacted to tumor bearing their respective antigen.  FIG. 7C &amp; 7D . 
     Example 3 
     CD20-CD79 A  Tandem Cars 
     Tandem CARs were constructed by fusing single domain V H H antibodies to the N-terminus of scFv containing CAR. An anti-CD20 V H H (SEQ ID NO: 20) was fused to the N-terminus of an anti-CD79a scFv CAR (SEQ ID NO: 28) to generate an anti-CD20 V H H-anti-CD79a scFv tandem CAR (SEQ ID NO: 30). An anti-CD79a scFv CAR (SEQ ID NO: 32) and an anti-CD20 V H H CAR (SEQ ID NO: 34) were also constructed. Monovalent CAR constructs and tandem CAR constructs were packaged into lentiviral particles and used to transduce human PBMCs in vitro. 
     Transduced human T cells were assessed for monovalent or tandem CAR expression by labeling with fluorescent antigen. In the case of CD20, no soluble fluorescent antigen was available so VHH expression was assessed with an anti-VHH antibody. The tandem construct was recognized with the anti-VHH antibody, indicating positive expression of the single domain moiety. The anti-CD79a scFv domain of the tandem construct was labeled with recombinant CD79a antigen. The degree of expression, as approximated by surface staining, was equivalent to the monovalent, single antigen targeting, constructs. An anti-CD19 scFv CAR was included as a control.  FIG. 8A . 
     Transduced T cells were subsequently co-cultured with antigen positive A549 tumor cells (CD19 +  or CD20 + ) at an effector: tumor ratio (E:T) of 1:1 and cytotoxicity was monitored over time using an Incucyte S3. After 48h of tumor co-culture, cytotoxicity was calculated from the area under the curve of co-cultured cells vs. tumor alone. In parallel, the transduced T cells were also incubated with Daudi tumor cells which express all three targeted antigens (CD19, CD20, and CD79a). The tandem CAR demonstrated cytolytic capacity against CD20 +  A549 cells, but not CD19 +  A549 cells, as there is no anti-CD19 component in the tandem CAR. The tandem CAR also showed cytotoxicity against CD20 +  A549 cells that was equivalent to the monovalent anti-CD20 V H H CAR.  FIG. 8B . 
     Cytokine secretion from cells modified with the CAR constructs and co-cultured with antigen positive tumor cells was evaluated at 24 hrs. using the Intellicyt MultiCyt QBeads Plexscreen secreted assay kit. Cytokine secretion from T cells transduced with the tandem CAR was comparable to T cells transduced with the monovalent CARs and was shown to be antigen specific and dependent.  FIG. 8C and 8D . 
     In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.