Title of Invention: GENERATION AND USE IN ADOPTIVE IMMUNOTHERAPY OF STEM CELL-LIKE MEMORY T CELLS Abstract: Provided herein are methods of generating antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, utilizing stem cell-like memory T cells (TSCM cells). Also disclosed are antigen-specific T cells generated by such methods, and methods of treating a human patient using such antigen-specific T cells. Detailed Description: CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 62/399,311, filed on Sep. 23, 2016, which is incorporated by reference herein in its entirety. GOVERNMENT RIGHTS STATEMENT This invention was made with government support under CA023766 awarded by National Institutes of Health. The government has certain rights in the invention. REFERENCE TO SEQUENCE LISTING SUBMITTED ELECTRONICALLY This application incorporates by reference a Sequence Listing submitted with this application as a text file entitled “Seqlisting_770-230-2665.txt” created on Sep. 12, 2017 and having a size of 4.57 kilobytes. 1. FIELD Provided herein are methods of generating antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, utilizing stem cell-like memory T cells (TSCM cells). Also disclosed are antigen-specific T cells generated by such methods, and methods of treating a human patient using such antigen-specific T cells. 2. BACKGROUND The characteristics of the T cells that are selected for expansion and adoptive transfer have been identified as a critical factor that determines the persistence of transferred cells. Antigen-specific T cells in the presence of infections or cancer can expand and differentiate into effector T cells devoted to rapidly clearing of the pathogens as well as memory T cells that can persist long-term and defend against recurrence of disease. The memory T cell compartment is heterogeneous and encompasses multiple subsets with distinctive properties. Current evidence indicates that central memory T cells (TCM cells) that express high levels of CD62L and CCR7 are less differentiated, while CD62L−CCR7− effector memory T cells (TEM cells) represent committed progenitor cells that undergo terminal differentiation (Berger et al., 2008, J Clin Invest 118:294-305). Furthermore, studies in mice and nonhuman primates have shown that infused T cells that are derived from the TCM population exhibit greater replicative potential in response to antigen and prolonged in vivo persistence compared with those derived from the TEM population (Berger et al., 2008, J Clin Invest 118:294-305; Wang et al., 2011, Blood 117:1888-1898). Recently, the spectrum of immunological memory has been extended with the identification of stem cell-like memory T cells (TSCM cells) that express CD45RA, CCR7 and CD62L, like naive T cells, but also express CD95. Human TSCM cells have been expanded in vitro (Gattinoni et al., 2011, Nat Med 17:1290-1297; Cieri et al., 2013, Blood 121:573-584). When compared with other memory T cell populations, human TSCM cells have exhibited increased proliferative capacity. TSCM cells transduced to express a mesothelin-specific chimeric antigen receptor have also exhibited greater proliferation and superior antitumor responses following adoptive transfer in a humanized mouse model (Gattinoni et al., 2011, Nat Med 17:1290-1297). While TSCM cells can differentiate into TCM, TEM and effector T cells, they also have a marked potential for self-renewal as shown by serial transplantation experiments (Cieri et al., 2013, Blood 121:573-584). Because of these attributes, TSCM cells have attracted considerable interests as a potential critical reservoir of antigen-specific T cells for reconstituting immunity following human allogeneic hematopoietic cell transplants (allo HCT) (Cieri et al., 2013, Blood 121:573-584; Xu et al., 2015, J Hematol Oncol 8:113; Biasco et al., 2015, Sci Transl Med 7:273ra213; Roberto et al., 2015, Blood 125:2855-2864). Indeed, analyses of T cell receptor CDR3 sequences have shown that TSCM cells undergo marked proliferation and clonal diversification early after allo HCT (Roberto et al., 2015, Blood 125:2855-2864; Cieri et al., 2015, Blood 125:2865-2874). Furthermore, TSCM cell clones, distinguished by retroviral vector insertion sites, may resist in humans for up to 12 years post infusion (Biasco et al., 2015, Sci Transl Med 7:273ra213). The low frequency of antigen-specific TSCM cells has limited their detailed characterization (Schmueck-Henneresse et al., 2015, J Immunol 194:5559-5567). Furthermore, the contribution of different memory subsets to the maintenance of the overall memory compartment of antigen-specific T cells has not been fully elucidated. Citation of a reference herein shall not be construed as an admission that such is prior art to the present disclosure. 3. SUMMARY OF THE INVENTION The present invention provides methods of generating antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, utilizing stem cell-like memory T cells (TSCM cells). Also disclosed are antigen-specific T cells generated by such methods, and methods of treating a human patient using such antigen-specific T cells. In one aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, comprising: (a) ex vivo sensitizing a population of human blood cells to one or more antigens of the pathogen or cancer over a period of time in culture, wherein at the initiation of said period of time, the population of human blood cells contains at least 50% stem cell-like memory T cells (TSCM cells); and (b) cryopreserving (i) the ex vivo sensitized population of human blood cells, or (ii) cells derived therefrom that comprise antigen-specific T cells recognizing the one or more antigens of the pathogen or cancer; thereby producing said population of cells comprising antigen-specific T cells. In certain embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the ex vivo sensitized population of human blood cells or cells derived therefrom. In specific embodiments, the aforementioned period of time in culture (termed herein “the Sensitization Culture Time;” i.e., the culture time period over which sensitization occurs) is in the range of 9-21 days. In a specific embodiment, the Sensitization Culture Time is in the range of 9-14 days. In another specific embodiment, the Sensitization Culture Time is 14 days. In specific embodiments, the ex vivo sensitizing step comprises co-culturing the population of human blood cells with one or more immunogenic peptides or proteins derived from the one or more antigens. In specific embodiments, the ex vivo sensitizing step comprises co-culturing the population of human blood cells with antigen presenting cells that present the one or more antigens. The antigen presenting cells used in the ex vivo sensitizing step can be any antigen presenting cells suitable for presenting the one or more antigens, such as dendritic cells, cytokine-activated monocytes, peripheral blood mononuclear cells (PBMCs), Epstein-Barr virus-transformed B-lymphoblastoid cell line cells (EBV-BLCL cells), or artificial antigen presenting cells (AAPCs). In a specific embodiment, the antigen presenting cells are AAPCs. In some embodiments, the antigen presenting cells are loaded with one or more immunogenic peptides or proteins derived from the one or more antigens. In other embodiments, the antigen presenting cells are genetically engineered to recombinantly express one or more immunogenic peptides or proteins derived from the one or more antigens. In some embodiments, the one or more immunogenic peptides or proteins are a pool of overlapping peptides derived from the one or more antigens. In specific embodiments, the pool of overlapping peptides is a pool of overlapping pentadecapeptides. In other embodiments, the one or more immunogenic peptides or proteins are one or more proteins derived from the one or more antigens. In some embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that endogenously express a public T cell receptor (TCR) recognizing the one or more antigens. In other embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that recombinantly express a public TCR recognizing the one or more antigens. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells, as described herein, further comprises transducing the population of human blood cells with a nucleic acid encoding a public TCR (e.g., at a time when the population of human blood cells has been cultured for 3-5 days). In a specific embodiment wherein the one or more antigens is cytomegalovirus (CMV) pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a complementarity determining region (CDR)3 of CASSPQTGASYGYTF (SEQ ID NO:3). In another specific embodiment wherein the one or more antigens is CMV pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPKTGAVYGYTF (SEQ ID NO:4). In certain embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that recombinantly express a chimeric antigen receptor (CAR) recognizing the one or more antigens. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells, as described herein, further comprises transducing the population of human blood cells with a nucleic acid encoding a CAR (e.g., at a time when the population of human blood cells has been cultured for 3-5 days). In another aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, comprising transducing a population of human blood cells with a nucleic acid encoding a public TCR recognizing one or more antigens of the pathogen or cancer at a time when the population of human blood cells has been cultured for 3-5 days, wherein the population of human blood cells contains at least 50% TSCM cells; thereby producing said population of cells comprising antigen-specific T cells. In a specific embodiment wherein the one or more antigens is CMV pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPQTGASYGYTF (SEQ ID NO:3). In another specific embodiment wherein the one or more antigens is CMV pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPKTGAVYGYTF (SEQ ID NO:4). In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of transducing, a step of cryopreserving the transduced population of human blood cells or cells derived therefrom. In a specific embodiment, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the transduced population of human blood cells or cells derived therefrom. In another aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a CMV infection, comprising transducing a population of human blood cells with a nucleic acid encoding a public TCR recognizing CMV pp65 at a time when the population of human blood cells has been cultured for 3-5 days, wherein the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPQTGASYGYTF (SEQ ID NO:3), and wherein the population of human blood cells contains at least 50% TSCM cells; thereby producing said population of cells comprising antigen-specific T cells. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of transducing, a step of cryopreserving the transduced population of human blood cells or cells derived therefrom. In a specific embodiment, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the transduced population of human blood cells or cells derived therefrom. In another aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a CMV infection, comprising transducing a population of human blood cells with a nucleic acid encoding a public TCR recognizing CMV pp65 at a time when the population of human blood cells has been cultured for 3-5 days, wherein the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPKTGAVYGYTF (SEQ ID NO:4), and wherein the population of human blood cells contains at least 50% TSCM cells; thereby producing said population of cells comprising antigen-specific T cells. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of transducing, a step of cryopreserving the transduced population of human blood cells or cells derived therefrom. In a specific embodiment, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the transduced population of human blood cells or cells derived therefrom. In another aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, comprising transducing a population of human blood cells with a nucleic acid encoding a CAR recognizing one or more antigens of the pathogen or cancer at a time when the population of human blood cells has been cultured for 3-5 days, wherein the population of human blood cells contains at least 50% TSCM cells; thereby producing said population of cells comprising antigen-specific T cells. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of transducing, a step of cryopreserving the transduced population of human blood cells or cells derived therefrom. In a specific embodiment, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the transduced population of human blood cells or cells derived therefrom. The population of human blood cells used in accordance with the methods of generating a population of cells comprising antigen-specific T cells described herein contains at least 50% TSCM cells. In a specific embodiment, the population of human blood cells contains at least 90% TSCM cells. In another specific embodiment, the population of human blood cells contains at least 95% TSCM cells. In another specific embodiment, the population of human blood cells contains at least 99% TSCM cells. In another specific embodiment, the population of human blood cells contains 100% TSCM cells. In certain embodiments, the population of human blood cells contains less than 10% TN cells. In a specific embodiment, the population of human blood cells contains less than 5% TN cells. In another specific embodiment, the population of human blood cells contains less than 1% TN cells. In another specific embodiment, the population of human blood cells contains no TN cells. In certain embodiments, the method of generating a population of cells comprising antigen-specific T cells described herein further comprises a step of deriving the population of human blood cells from a human cell sample. In specific embodiments, the deriving step comprises enriching for TSCM cells from the human cell sample. In a specific embodiment, the enriching step comprises selecting for cells that are CD3+CD62L+CD45RO−CD95+. In some embodiments, the step of deriving the population of human blood cells from a human cell sample comprises sorting TSCM cells from the human cell sample by fluorescence-activated cell sorting (FACS). In preferred embodiments, the population of human blood cells is derived from a human donor that is seropositive for the one or more antigens. In certain embodiments, the population of cells comprising antigen-specific T cells, as described herein, lacks substantial cytotoxicity in vitro toward antigen presenting cells that are not loaded with or genetically engineered to express one or more peptides or proteins derived from the one or more antigens. In specific embodiments of the methods of generating a population of cells comprising antigen-specific cells described herein, the ex vivo sensitizing step comprises ex vivo sensitizing the population of human blood cells to one or more antigens of the pathogen. The pathogen can be a virus, bacterium, fungus, helminth or protist. In some embodiments, the pathogen is a virus. In a specific embodiment, the virus is cytomegalovirus (CMV). In specific embodiments of the methods of generating a population of cells comprising antigen-specific cells described herein, the ex vivo sensitizing step comprises ex vivo sensitizing the population of human blood cells to one or more antigens of Epstein-Barr virus (EBV). In specific embodiments of the methods of generating a population of cells comprising antigen-specific cells described herein, the ex vivo sensitizing step comprises ex vivo sensitizing the population of human blood cells to one or more antigens of BK virus (BKV), John Cunningham virus (JCV), herpesvirus, adenovirus (ADV), human immunodeficiency virus (HIV), influenza virus, ebola virus, poxvirus, rhabdovirus, or paramyxovirus. In specific embodiments of the methods of generating a population of cells comprising antigen-specific cells described herein, the ex vivo sensitizing step comprises ex vivo sensitizing the population of human blood cells to one or more antigens of the cancer. The cancer can be a blood cancer. In a specific embodiment, the cancer is multiple myeloma or plasma cell leukemia. In an aspect of the specific embodiment, the one or more antigens of the cancer is Wilms tumor 1 (WT1). The cancer can also be a solid tumor cancer, such as, but is not limited to: a cancer of the breast, lung, ovary, stomach, pancreas, larynx, esophagus, testes, liver, parotid, biliary tract, colon, rectum, cervix, uterus, endometrium, kidney, bladder, prostate, thyroid, brain, or skin. In another aspect, provided herein are methods of treating a human patient having a pathogen or cancer, comprising: (i) generating a population of cells comprising antigen-specific T cells according to a method described herein; and (ii) administering the population of cells comprising antigen-specific T cells to the human patient. In another aspect, provided herein are methods of treating a human patient having a pathogen or cancer, comprising administering a population of cells comprising antigen-specific T cells to the human patient, wherein the population of cells comprising antigen-specific T cells is the product of a method comprising generating the population of cells comprising antigen-specific T cells according to a method described herein. In some embodiments, the antigen-specific T cells contained in the population of cells comprising antigen-specific T cells are restricted by an HLA allele shared with the diseased cells in the human patient to be treated. In other embodiments, the antigen-specific T cells contained in the population of cells comprising antigen-specific T cells share at least 2 HLA alleles (for example, at least 2 out of 8 HLA alleles, such as two HLA-A alleles, two HLA-B alleles, two HLA-C alleles, and two HLA-DR alleles) with the diseased cells in the human patient to be treated. In specific embodiments, the population of human blood cells is derived from a human donor that is allogeneic to the human patient. In a specific embodiment, the human patient has been the recipient of a transplant from a transplant donor, and the human donor is a third-party donor that is different from the transplant donor. In some embodiments, the administering step comprises administering the population of cells comprising antigen-specific T cells to the human patient, at a dose that is less than or equal to about 1×105 cells of the population of cells comprising antigen-specific T cells per kg of the human patient. In a specific embodiment, the administering step comprises administering the population of cells comprising antigen-specific T cells to the human patient, at a dose that is less than or equal to about 5×104 cells of the population of cells comprising antigen-specific T cells per kg of the human patient. In a preferred embodiment, the administering step comprises administering the population of cells comprising antigen-specific T cells to the human patient, at a dose that is less than or equal to about 1×104 cells of the population of cells comprising antigen-specific T cells per kg of the human patient. In another specific embodiment, the administering step comprises administering the population of cells comprising antigen-specific T cells to the human patient, at a dose that is less than or equal to about 5×103 cells of the population of cells comprising antigen-specific T cells per kg of the human patient. In another specific embodiment, the administering step comprises administering the population of cells comprising antigen-specific T cells to the human patient, at a dose that is less than or equal to about 1×103 cells of the population of cells comprising antigen-specific T cells per kg of the human patient. In certain embodiments, the step of administering comprises administering the population of cells comprising antigen-specific T cells to the human patient at the dose described above weekly. In certain embodiments, the step of administering is by bolus intravenous infusion. In certain embodiments, the step of administering comprises administering at least 2 doses of the population of cells comprising antigen-specific T cells to the human patient. In specific embodiments, the step of administering comprises administering 2, 3, 4, 5, or 6 doses of the population of cells comprising antigen-specific T cells to the human patient. In a specific embodiment, the step of administering comprises administering a first cycle of one dose per week of the population of cells comprising antigen-specific T cells for 3 consecutive weeks followed by a washout period during which no dose of the population of cells comprising antigen-specific T cells is administered, followed by a second cycle of said one dose per week of the population of cells comprising antigen-specific T cells for 3 consecutive weeks. In specific embodiments, the step of administering comprises administering two, three, four, five, or six cycles of one dose per week of the population of cells comprising antigen-specific T cells for three consecutive weeks, each cycle separated by a washout period during which no dose of the population of cells comprising antigen-specific T cells is administered. In specific embodiments, the washout period is about 1, 2, 3, or 4 weeks. In a preferred embodiment, the washout period is about 3 weeks. In specific embodiments, the step of administering of the population of cells comprising antigen-specific T cells does not result in any graft-versus-host disease (GvHD) in the human patient. In another aspect, provided herein are populations of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, wherein the population of cells comprising antigen-specific T cells is the product of a method comprising generating the population of cells comprising antigen-specific T cells according to a method described herein. In specific embodiments, provided herein is a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, wherein the population of cells comprising antigen-specific T cells is the product of a method comprising generating the population of cells comprising antigen-specific T cells according to a method described herein, and wherein the population of cells comprising antigen-specific T cells is cryopreserved. In another aspect, provided herein is a cell bank comprising a plurality of populations of cells comprising antigen-specific T cells described herein. 4. BRIEF DESCRIPTION OF FIGURES FIG. 1. Isolation and characterization of TN, TSCM, TCM and TEM populations from human peripheral blood. Flow cytometry was used to isolate the TN, TSCM, TCM and TEM subsets from peripheral blood mononuclear cell (PBMCs). Lymphocytes were first gated within PBMCs by forward scatter (FSC) and side scatter (SCC) and analyzed for CD45RO, CD95, CD62L and CD3 expression. CD3+ lymphocytes were then gated for CD45RO+CD62L+ TCM and CD45RO+CD62L− TEM, CD45RO−CD62L+CD95+ TSCM cells and CD45RO−CD62L+CD95− TN cells. FIG. 2. Phenotypic characterization of naive and memory (TN, TSCM, TCM and TEM)-derived CMV-specific CD8+ T cells upon antigen stimulation. (A), (B) and (C) Isolated T cells from TN, TSCM, TCM and TEM cell populations were sensitized with artificial antigen presenting cells (AAPCs) expressing CMVpp65 peptide and HLA-A:0201. CD3+ T lymphocytes derived from each cell population were evaluated at 7 (A), 14 (B) and 30 days (C) post-stimulation. CD8+ single, live T cells were gated from CD3+ T lymphocytes. HLA-A:0201-NLV Tetramer (Tet)+ and NLV-Tet− T cells were then gated within CD8+ T cells (left panel). Expression frequencies of CD62L, CCR7 and CD45RA gated on NLV-Tet+ and NLV-Tet− population are shown for a representative donor. (Regular font text: NLV-Tet+; Bold font text: NLV-Tet−.) (FIGS. 2A-2C were originally in color, so for purposes of this black and white reproduction of the figures, outlines of the former blue FACS plot contours were traced manually in order to make them distinguishable on black and white reproduction from the former red contours, the outlines of which were not traced.) Percentages of CCR7+ cells 14 days post-stimulation are shown in (D) for NLV-Tet+ and in (E) for NLV-Tet− T cells (n=6; *P<0.05; **P<0.01; from Mann-Whitney test). FIG. 3. Distinct expression of co-stimulatory and senescence markers within TN, TSCM, TCM and TEM. Expression frequencies of CD27, CD57, CD127, CD28, KLRG1 and PD1 gated on NLV-Tet+ and NLV-Tet− populations after in-vitro stimulation for 14-18 days are shown. (A) Percentage of CD27+ cells within NLV-Tet+ CD8+ T cells (n=6) derived from TN, TSCM, TCM and TEM populations, respectively. (B) Representative fluorescence-activated cell sorting (FACS) plots of the CD27 expression within CD8+ T cells. (C) Percentage of NLV-Tet+ CD8+ T cells expressing CD57 (n=8) derived from TN, TSCM, TCM and TEM populations, respectively. (D) Representative FACS plots of the CD57 expression in CD8+ T cells. (E) and (F) Percentage of NLV-Tet+ CD8+ T cells expressing CD 127 (n=6) and CD28 (n=8) respectively, derived from TN, TSCM, TCM and TEM populations, respectively. (G) and (H) Percentage of CD8+ T cells expressing KLRG1 within NLV-Tet+ (G) and NLV-Tet− T cells post-stimulation (n=9). (I) and (J) Percentage of CD8+ T cells expressing PD1 within NLV-Tet+ (I) and NLV-Tet− (J) T cells post-stimulation (n=11). (*P<0.05; **P<0.01; ***P<0.005; from Mann-Whitney test.) FIG. 4. Enrichment of CMV-specific CD8+ T cells results from rapid expansion of early memory T cells. (A) In-vitro proliferation of A2-NLV-Tet+ T cells was evaluated after in-vitro sensitization with CMVpp65 antigen by EdU as shown in a representative donor on Day 3, 5 and 7 post-stimulation. CD3+ T cells were sensitized with artificial antigen presenting cells (AAPCs) expressing CMVpp65 peptide and HLA-A*0201. The enrichment of NLV-Tet+ T cells after stimulation was evaluated as shown on the left panel. Percentage of EdU incorporation gated on single, live CD8+ T lymphocytes is shown in the middle panel. Percentage of EdU incorporation gated on NLV-Tet+ CD8+ T cells is shown on the right panel. (B) Phenotypic analysis of NLV-Tet+ T cells (right panel) in comparison to NLV-Tet+ T cells with EdU incorporation (left panel) is shown for a representative donor. (White: CD45RO+CD62L− TEM; Light Grey: CD45RO+CD62L+ TCM; Dark Grey: CD45RO−CD62L+CD95+ TSCM.) CD45RO−CD62L+CD95− TN cells were not detected post antigen stimulation. (C) Fold expansion of A2-NLV-Tet+ T cells after 14 days of antigen-specific T cell stimulation was evaluated within NLV-Tet+ CD8+ T cells within the TN-, TSCM-, TCM- and TEM-derived cells. NLV-Tet+ CD8+ T cells were not detected before exposure to antigen in 4 out of 6 donors for the TN population (n=6) (*P=0.03; ns, not significant; from Mann-Whitney test). FIG. 5. Functional cytokine profile and cytotoxic activity of in vitro expanded CMV-specific T cells derived from naive (TN) and memory T cells (TSCM, TCM and TEM). (A) Expanded naive and memory T cell populations were stimulated for 18 hours with NLV peptide loaded autologous B-lymphoblastoid cell line cells (BLCL cells) at a ratio of 5:1. T cells co-cultured with autologous BLCLs without peptide loading served as controls. CD8+ T cells secreting IFN-γ and TNF-α were evaluated by intracellular staining. The percentage of CD8+ T cells expressing CD137 are shown on the first 2 panels (on FIG. 5A-1) with or without peptide stimulation. The proportion of CD8+ T cells expressing CD137 and secreting IFN-γ or TNF-α cytokine is shown in the next 2 panels (on FIG. 5A-2). CD8+ T cells secreting both IFN-γ and TNF-α cytokine are shown in the last panel (on FIG. 5A-2). (B) Cytotoxic activity was evaluated by CD107a degranulation assay. The percentage of CD8+ T cells expressing CD107a with (middle panel) or without (left panel) peptide stimulation is shown. The percentage of CD8+ T cells expressing both CD137 and CD107a is shown in the right panel. Data shown is a representative of three experiments (n=3). FIG. 6. Clonal diversity and clonotype selection within CMV-specific TN, TSCM, TCM and TEM cells. Next-generation sequencing was performed for TCRVβ repertoire analysis. TCR clonality was analyzed using immuno SEQ Analyzer 2.0 (A) before and (B) 15 days after T cell expansion, for NLV-Tet+ T cells contained within (A) sorted TN, TSCM, TCM and TEM subsets or (B) cells derived from these subsets, respectively. Heat map indicates similarity of sample profiles. The similarity accounts for overlap between unique nucleotide sequences within any two samples. (c) Sorted NLV-Tet+ T cells derived from Naive (TN), and memory (TSCM, TCM and TEM) subsets from the same donor after 30 days expansion were compared for their TCR sequences. TCR sequencing was performed on sorted NLV-Tet+ T cells derived from Naive (TN), and memory (TSCM, TCM and TEM) subsets from a separate donor (D) before, (E) after 15 days and, (F) after 30 days of in vitro stimulation, and compared for their similarities. Values shown are proportions of overlap. The TCR sequencing analysis for this donor at the same time points (pre-, day 15 and day 30 post-stimulation) is summarized in (G). FIG. 7. Enhanced proliferation of TSCM cells may not explain immunodominance. (A) T cells from HLA-A:0201+ and A:2402+ CMV seropositive donors were sensitized with artificial antigen presenting cells (AAPCs) expressing HLA-A:0201 or HLA-A:2402 and CMVpp65 protein. T cells gated on single, live CD8+ T lymphocytes were gated for cells binding the HLA-A:0201-NLVPMVATV (SEQ ID NO:1) peptide tetrameric complexes (NLV-Tet+) or HLA-A:2402-QYDPVAALF (SEQ ID NO:2) peptide tetrameric complexes (QYD-Tet+) after 4, 5, 7 and 8 days post antigen specific stimulation (n=2). Results are shown for one representative donor. Phenotypic analysis of NLV-Tet+ or QYD-Tet+ T cells was performed to evaluate the proportion of TSCM, TCM and TEM-derived cells after antigen specific stimulation (CD45RO+CD62L+ TCM: Light Gray; CD45RO+CD62L− TEM: White; CD45RO−CD62L+CD95+ TSCM: Dark Gray). There were no Tet+ T cells with TN phenotype CD45RO−CD62L+CD95− post-sensitization. (B) T cells labeled with EdU were used to evaluate and compare the proportion of proliferating T cells within NLV-Tet+ and the proportion of proliferating T cells within QYD-Tet+ T cells, within TSCM-, TCM- and TEM-derived cells 4, 5, 7 and 8 days post stimulation (FIG. 7B-1). The proportion of apoptotic T cells within EdU labeled NLV-Tet+ or EdU labeled QYD-Tet+ population was evaluated after T cell stimulation at 4, 5, 7 and 8 days using Annexin V labeling (FIG. 7B-2). 5. DETAILED DESCRIPTION The present invention provides methods of generating antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, antigen-specific T cells generated by such methods, and methods of treating a human patient using such antigen-specific T cells. According to the present invention, stem cell-like memory T cells (TSCM cells) are a more suitable source of T cells for the generation of antigen-specific T cells for adoptive immunotherapy, relative to naive T cells (TN cells), central memory T cells (TCM cells) and effector memory T cells (TEM cells), because they allow rapid, persistent and selective in vitro expansion of antigen-specific T cells that recognize dominant epitopes of antigens of pathogens found in human blood and are the principal and persistent reservoir for rapid repopulation of immunodominant T cells in vivo. 5.1. Methods of Generating Antigen-Specific T Cells for Adoptive Immunotherapy 5.1.1. Methods Using Ex Vivo Sensitization of TSCM Cells In one aspect, provided herein are methods of generating a population of cells comprising antigen-specific T cells for therapeutic administration to a human patient having or suspected of having a pathogen or cancer, comprising: (a) ex vivo sensitizing a population of human blood cells to one or more antigens of the pathogen or cancer over a period of time in culture, wherein at the initiation of said period of time, the population of human blood cells contains at least 50% stem cell-like memory T cells (TSCM cells); and (b) cryopreserving (i) the ex vivo sensitized population of human blood cells, or (ii) cells derived therefrom that comprise antigen-specific T cells recognizing the one or more antigens of the pathogen or cancer; thereby producing said population of cells comprising antigen-specific T cells. Ex Vivo Sensitization In specific embodiments, the aforementioned period of time in culture (termed herein “the Sensitization Culture Time;” i.e., the culture time period over which sensitization occurs) is in the range of 9-21 days. As will be clear, this means that the period of time in culture for sensitization purposes starting with the first culturing in the presence of antigen until the end of culturing in the presence of antigen is only for 9-21 days and not longer. (The cells may optionally be cultured for a longer period of time, but not in the presence of antigen for sensitization.) In a specific embodiment, the Sensitization Culture Time is in the range of 9-14 days. In another specific embodiment, the Sensitization Culture Time is 9 days. In another specific embodiment, the Sensitization Culture Time is 10 days. In another specific embodiment, the Sensitization Culture Time is 11 days. In another specific embodiment, the Sensitization Culture Time is 12 days. In another specific embodiment, the Sensitization Culture Time is 13 days. In another specific embodiment, the Sensitization Culture Time is 14 days. In another specific embodiment, the Sensitization Culture Time is 15 days. In another specific embodiment, the Sensitization Culture Time is 16 days. In another specific embodiment, the Sensitization Culture Time is 17 days. In another specific embodiment, the Sensitization Culture Time is 18 days. In another specific embodiment, the Sensitization Culture Time is 19 days. In another specific embodiment, the Sensitization Culture Time is 20 days. In another specific embodiment, the Sensitization Culture Time is 21 days. The ex vivo sensitizing step can be performed by any method known in the art to stimulate T cells to be antigen-specific ex vivo, such as a method as described in Koehne et al., 2000, Blood 96:109-117; Trivedi et al., 2005, Blood 105:2793-2801; Haque et al., 2007, Blood 110:1123-1131; Hasan et al., 2009, J Immunol 183: 2837-2850; Feuchtinger et al., 2010, Blood 116:4360-4367; Doubrovina et al., 2012, Blood 120:1633-1646; Leen et al., 2013, Blood 121:5113-5123; Papadopoulou et al., 2014, Sci Transl Med 6:242ra83; Sukdolak et al., 2013, Biol Blood Marrow Transplant 19:1480-1492; Koehne et al., 2015, Biol Blood Marrow Transplant 21: 1663-1678, or International Patent Application Publication No. WO 770-230-2665. In specific embodiments, the ex vivo sensitizing step comprises co-culturing the population of human blood cells with one or more immunogenic peptides or proteins derived from the one or more antigens (preferably also in the presence of antigen presenting cells). In specific embodiments, the ex vivo sensitizing step comprises co-culturing the population of human blood cells with antigen presenting cells that present the one or more antigens. The ex vivo sensitizing step preferably comprises first supplementing the culture with IL-15 and IL-7 (e.g., starting from day 4 after the initiation of the Sensitization Culture Time, or earlier), and then supplementing the culture with IL-2 (e.g., at least 7 days after the initiation of the Sensitization Culture Time) optionally together with IL-15 and IL-7. IL-15 and IL-7 help to maintain stem cell-like phenotype of the TSCM cells, and are preferably added to the culture within the first seven days of culturing in the ex vivo sensitizing step and then again for multiple times. IL-2 helps to boost expansion of the antigen-specific T cells, and is preferably added to the cell culture on a culture date that is later than the initial addition of IL-15 and IL-7 to the cell culture in the ex vivo sensitizing step (e.g., IL-2 is added at least 7 days after the initiation of the Sensitization Culture Time). In a specific embodiment, the ex vivo sensitizing step comprises supplementing the culture with IL-15 and IL-7 on day 4 and day 7 after the initiation of the Sensitization Culture Time, and then supplementing the culture with IL-15, IL-7 and IL-2 every other day starting after day 12 after the initiation of the Sensitization Culture Time. The antigen presenting cells used in the ex vivo sensitizing step can be any antigen presenting cells suitable for presenting the one or more antigens, such as dendritic cells, cytokine-activated monocytes, peripheral blood mononuclear cells (PBMCs), Epstein-Barr virus-transformed B-lymphoblastoid cell line cells (EBV-BLCL cells), or artificial antigen presenting cells (AAPCs). In a specific embodiment, the antigen presenting cells are dendritic cells. In another specific embodiment, the antigen presenting cells are PBMCs. In another specific embodiment, the antigen presenting cells are EBV-BLCL cells. In another specific embodiment, the antigen presenting cells are AAPCs. In certain embodiments, the antigen presenting cells are derived from the donor of the population of human blood cells. The antigen presenting cells can be obtained by any method known in the art, such as the method(s) described in Koehne et al., 2000, Blood 96:109-117; Koehne et al., 2002, Blood 99:1730-1740; Trivedi et al., 2005, Blood 105:2793-2801; O'Reilly et al., 2007, Immunol Res 38:237-250; Hasan et al., 2009, J Immunol 183: 2837-2850; Barker et al., 2010, Blood 116:5045-5049; O' Reilly et al., 2011, Best Practice & Research Clinical Haematology 24:381-391; Doubrovina et al., 2012, Blood 120:1633-1646; Koehne et al., 2015, Biol Blood Marrow Transplant 21: 1663-1678, or International Patent Application Publication No. WO 770-230-2665. In some embodiments, the antigen presenting cells are loaded with one or more immunogenic peptides or proteins derived from the one or more antigens. Non-limiting exemplary methods for loading antigen presenting cells with peptide(s) derived from antigen(s) can be found in Trivedi et al., 2005, Blood 105:2793-2801; Hasan et al., 2009, J Immunol 183: 2837-2850; and International Patent Application Publication No. WO 770-230-2665. In other embodiments, the antigen presenting cells are genetically engineered to recombinantly express one or more immunogenic peptides or proteins derived from the one or more antigens. Any appropriate method known in the art for introducing nucleic acid vehicles into cells to express proteins, such as transduction or transformation, can be used to genetically engineer the antigen presenting calls to recombinantly express the one or more immunogenic peptides or proteins derived from the one or more antigens. In some embodiments, the one or more immunogenic peptides or proteins are a pool of overlapping peptides derived from the one or more antigens. In specific embodiments, the pool of overlapping peptides is a pool of overlapping pentadecapeptides. In other embodiments, the one or more immunogenic peptides or proteins are one or more proteins derived from the one or more antigens. Cryopreservation In preferred embodiments, the step of cryopreserving comprises steps of: (c) recovering from culture the ex vivo sensitized population of human blood cells or cells derived therefrom; (d) combining with a cryopreservative the ex vivo sensitized population of human blood cells or cells derived therefrom; and (e) freezing the ex vivo sensitized population of human blood cells, or cells derived therefrom, combined with the cryopreservative. Cells derived from the ex vivo sensitized population of human blood cells and comprising antigen-specific T cells which recognize the one or more antigens of the pathogen or cancer can be a fraction of the ex vivo sensitized population of human blood cells (e.g., a CD3+ T cell population enriched from the ex vivo sensitized population of human blood cells, or a CD8+ cytotoxic T cell population enriched from the ex vivo sensitized population of human blood cells) or an expanded population of the ex vivo sensitized population of human blood cells. Freezing of cells is ordinarily destructive. On cooling, water within the cell freezes. Injury then occurs by osmotic effects on the cell membrane, cell dehydration, solute concentration, and ice crystal formation. As ice forms outside the cell, available water is removed from solution and withdrawn from the cell, causing osmotic dehydration and raised solute concentration which eventually destroy the cell. (For a discussion, see Mazur, 1977, Cryobiology 14:251-272.) These injurious effects can be circumvented by (a) use of a cryopreservative, (b) control of the freezing rate, and (c) storage at a temperature sufficiently low to minimize degradative reactions. Cryopreservative which can be used in accordance with the present invention can be, but is not limited to, dimethyl sulfoxide (DMSO), glycerol, polyvinylpyrrolidine, polyethylene glycol, albumin, dextran, sucrose, ethylene glycol, i-erythritol, D-ribitol, D-mannitol, D-sorbitol, i-inositol, D-lactose, choline chloride, amino acids, methanol, acetamide, glycerol monoacetate, or inorganic salts. In a preferred embodiment, the cryopreservative which is used in accordance with the present invention is DMSO. Being a small molecule, DMSO freely permeates the cell and protects intracellular organelles by combining with water to modify its freezability and prevent damage from ice formation. Addition of plasma, fetal calf serum, or human albumin can augment the protective effect of DMSO. After addition of DMSO, cells should be kept at 0° C. until freezing, since DMSO concentrations of about 1% are toxic at temperatures above 4° C. A controlled slow cooling rate is also critical. Different cryopreservatives (Rapatz, G., et al., 1968, Cryobiology 5(1):18-25) and different cell types have different optimal cooling rates (see, e.g., Rowe and Rinfret, 1962, Blood 20:636; Rowe, 1966, Cryobiology 3:12-18; Lewis et al., 1967, Transfusion 7:17-32; and Mazur, 1970, Science 168:939-949). The heat of fusion phase where water turns to ice should be minimal. The cooling procedure can be carried out by use of, e.g., a programmable freezing device or a methanol bath procedure. Any method for cryopreserving that preserves viability of the cells can be used. In specific embodiments, a controlled rate freezer is used in the cryopreserving step to bring the temperature of the vial of cells to ≤−90° C. or less, at a rate ranging from −0.3 to −2° C. per minute. By way of example but not limitation, the following program can be used: 1) wait for chamber is 4° C. and sample is 6.0° C.; 2) crawfordsamuel@example.org° C./min. until sample is −6.0° C.; 3) ramp at 25° C./min. until chamber is −45° C.; 4) ramp at 10° C./min. until chamber is −14° C.; 5) crawfordsamuel@example.org° C./min. until chamber is −40° C.; 6) ramp at 10° C./min. until chamber is −90° C.; and 7) transfer to liquid nitrogen. Alternatively, the cells can be placed in a Mr. Frosty™ or other alcohol/polystyrene insulated freezing chamber pre-conditioned at −20° C. and frozen overnight by transferring the chamber to a −80° C. freezer, prior to transfer to liquid nitrogen storage. After thorough freezing, the ex vivo sensitized population of human blood cells or cells derived therefrom can be rapidly transferred to a long-term cryogenic storage vessel. In a preferred embodiment, the ex vivo sensitized population of human blood cells or cells derived therefrom can be cryogenically stored in liquid nitrogen (−196° C.) or its vapor (−165° C.). In a specific embodiment, the cells are stored at −80° C. for 2 days and then transferred to liquid nitrogen. In a specific embodiment, a plurality of the populations of cells comprising antigen-specific T cells are generated and stored as described herein, thereby producing a cell bank. In a preferred embodiment, by way of example but not limitation, the cryopreserving step is performed as follows: First, a freeze mix is prepared containing 90% fetal calf serum and 10% DMSO (in sterile, 15 ml tubes, 9 ml of heat inactivated and filtered fetal calf serum is mixed with sterile, filtered 1 ml of DMSO). Aliquots of this freeze mix are prepared under sterile conditions and then stored at −20° C. for use as a suspension medium for freezing cells. T cells suspended at 1×106/ml in Tcell medium are centrifuged in 15 or 50 ml tubes at 1500 rpm for 5 mins. The supernatant is gently discarded, cells are washed a second time with phosphate buffered saline (PBS), and cell pellet is then suspended in the thawed freeze mix at 10×106 cells/ml. Other known methods of cryopreservation of viable cells, or modifications thereof, are available and envisioned for use (e.g., cold metal-mirror techniques; Livesey and Linner, 1987, Nature 327:255; Linner et al., 1986, J Histochem Cytochem 34:1123-1135; see also U.S. Pat. No. 4,199,022 by Senkan et al., U.S. Pat. No. 3,753,357 by Schwartz, U.S. Pat. No. 4,559,298 by Fahy). In certain embodiments, the method of generating a population of cells comprising antigen-specific T cells further comprises, after the step of cryopreserving, steps of thawing and optionally expanding in culture the ex vivo sensitized population of human blood cells or cells derived therefrom. Frozen cells are preferably thawed quickly (e.g., in a water bath maintained at 37-41° C.) and chilled immediately upon thawing. In particular, the vial containing the frozen cells can be immersed up to its neck in a warm water bath; gentle rotation will ensure mixing of the cell suspension as it thaws and increase heat transfer from the warm water to the internal ice mass. As soon as the ice has completely melted, the vial can be immediately placed in ice. The cryopreservative, if toxic in humans, can be removed prior to therapeutic administration, and the removal is preferably accomplished upon thawing. However, when the cryopreservative is DMSO, it is preferable to omit this step in order to avoid cell loss, since DMSO in a low concentration has no serious toxicity. TCR- or CAR-Expression In some embodiments, the population of cells comprising antigen-specific T cells comprises antigen-specific T cells that recombinantly express a protein of interest, for example, a T cell receptor (TCR) or a chimeric antigen receptor (CAR). This can be achieved by transducing the population of human blood cells during their time in culture with a nucleic acid encoding the protein of interest. The nucleic acid preferably is a vector in which a nucleic acid sequence encoding the protein of interest is operably linked to a promoter. The transducing preferably occurs during days 3-5 in culture, since, as shown by the example section herein (i.e., Section 6), this time is when the TSCM cells exhibit the highest proliferative capacity. In some embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that endogenously express a public T cell receptor (TCR) recognizing the one or more antigens. In other embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that recombinantly express a public TCR recognizing the one or more antigens. In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells, as described herein, further comprises transducing the population of human blood cells with a nucleic acid encoding a public TCR (e.g., at a time when the population of human blood cells has been cultured for 3-5 days), for example, using a transducing method as described in Section 5.1.2, infra. The transducing step can be performed before, during, or after the ex vivo sensitizing step, which reduces alloreactivity of the population of cells comprising antigen-specific T cells. Public TCRs are peptide-specific TCRs with highly homologous sequences detected in multiple individuals (Li et al., 2012, Cell Res 22:33-42). Public TCRs for a variety of human viruses have been described (Argaet et al., 1994, J Exp Med 180:2335-2340; Wang et al., 2012, Sci Transl Med 4:128ra142; Nguyen et al., 2014, J Immunol 192:5039-5049; Trautmann et al., 2005, J Immunol 175:6123-6132). In a specific embodiment wherein the one or more antigens is cytomegalovirus (CMV) pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a complementarity determining region (CDR)3 of CASSPQTGASYGYTF (SEQ ID NO:3). In another specific embodiment wherein the one or more antigens is CMV pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of CASSPKTGAVYGYTF (SEQ ID NO:4). In another specific embodiment wherein the one or more antigens is CMV pp65, the public TCR comprises a β-chain comprising a variable domain, which comprises a CDR3 of S*nTG*nGY (SEQ ID NO:16; *n indicates any amino acid sequence of any length and any amino acid combination). In certain embodiments, the population of cells comprising antigen-specific T cells, as described herein, comprises antigen-specific T cells that recombinantly express a chimeric antigen receptor (CAR) recognizing the one or more antigens (see Section 5.1.3, infra, for more details regarding CAR). In specific embodiments, the method of generating a population of cells comprising antigen-specific T cells, as described herein, further comprises transducing the population of human blood cells with a nucleic acid encoding a CAR (e.g., at a time when the population of human blood cells has been cultured for 3-5 days), for example, using a transducing method as described in Section 5.1.3, infra. The transducing step can be performed before, during, or after the ex vivo sensitizing step, which reduces alloreactivity of the population of cells comprising antigen-specific T cells. 5.1.2. Methods Using TCR-Transduced TSCM Cells In another aspect, provided herein are methods of generating a population of cells comprising antigen-specific T
{'application_number': '<application-reference appl-type="utility">\n<document-id>\n<country>US</country>\n<doc-number>16333651</doc-number>\n<date>20170922</date>\n</document-id>\n</application-reference>', 'publication_number': '<publication-reference>\n<document-id>\n<country>US</country>\n<doc-number>20200009189</doc-number>\n<kind>A1</kind>\n<date>20200109</date>\n</document-id>\n</publication-reference>', 'source_file': './application/2020/ipa200109.xml', 'source_data': 'USPTO-Application'}