High efficiency TCR gene transfer into primary human lymphocytes affords avid recognition of melanoma tumor antigen glycoprotein 100 and does not alter the recognition of autologous melanoma antigens

The resting and ligand-bound states of the membrane-embedded human T-cell receptor-CD3 complex

The T-cell receptor (TCR) is central to the ligand-dependent activation of T lymphocytes and as such orchestrates both adaptive and pathologic immune processes. However, major questions remain regarding the structure and function of the human TCR. Here, we present cryogenic electron microscopy structures for the unliganded and HLA-bound human TCR-CD3 complex in nanodiscs that provide a native-like lipid environment. The unliganded structures reveal two related conformations that are distinct from its structure in detergent. These new "closed and compacted" conformations afford insights into the interactions between the TCR-CD3 and the membrane, including conserved surface patches that make extensive outer leaflet contact, and suggest novel conformational regulation by glycans. We show that the closed/compacted conformations, not the extended one previously reported in detergent, represent the unliganded resting state for the TCR-CD3 in vivo, underscoring the importance of structural interrogation of membrane proteins in native-like environments. By contrast, the structure of the HLA-bound complex in nanodiscs is in an open and extended conformation, showing that physiologic ligand binding is sufficient to induce substantial conformational change in the TCR-CD3 complex. We use conformation-locking disulfide mutants to show that ectodomain opening is necessary for maximal ligand-dependent TCR-CD3 activation, demonstrating that TCR-intrinsic conformational change is necessary for full TCR-CD3 activation and opening numerous avenues for immunoreceptor engineering.

Antigen/HLA-agnostic strategies for Characterizing Tumor-responsive T cell receptors in PDAC patients via single-cell sequencing and autologous organoid application

Characterization of tumor-responsive T cell receptors (TCRs) is a critical step in personalized TCR-T cell therapy, and remains challenging for pancreatic ductal adenocarcinoma (PDAC). Here we report a proof-of-concept study to identify and validate antitumor TCRs in two representative PDAC patients using ultradeep single-cell TCR/RNA sequencing and autologous organoids, and reveal the phenotypic dynamics of TCR repertoire in different T cell expansions from the same patient. We first performed comparative sequencing on freshly harvested peripheral blood mononuclear cells (PBMCs) and uncultured tumor infiltrating lymphocytes (TILs), followed by reactivity tests of TIL-enriched TCRs with autologous organoids, in which two tumor-responsive TCRs were successfully characterized and the corresponding TILs were mostly tissue-resident memory-like T cells, and partially expressed both naïve and exhausted T cell markers. For the PDAC patient without high-quality TILs, PBMCs were cultured with neoantigen peptide (KRASG12D), organoids, or anti-CD3 antibody in presence, and experienced extensive clonal expansions within ten days. All derived PBMCs were sequenced in parallel (>82,000 cells), and TCRs enriched in both peptide- and organoid-experienced, but not anti-CD3-treated CD8 T cells, were assessed for their reactivity to antigen-presenting cells (APCs) and organoids, in which three neoantigen-reactive TCRs were identified as tumor-responsive, and the corresponding T cells were characterized by mixed transcriptional signatures including but not limited to typical exhausted T cell markers. Together, our study revealed that the combination of ultradeep single-cell sequencing and organoid techniques enabled rapid characterization of tumor-responsive TCRs for developing practical personalized TCR-T therapy in an antigen/human leukocyte antigen (HLA)-agnostic manner.

Melanoma Antigen Family A (MAGE A) as Promising Biomarkers and Therapeutic Targets in Bladder Cancer

The Melanoma Antigen Gene (MAGE) is a large family of highly conserved proteins that share a common MAGE homology domain. Interestingly, many MAGE family members exhibit restricted expression in reproductive tissues but are abnormally expressed in various human malignancies, including bladder cancer, which is a common urinary malignancy associated with high morbidity and mortality rates. The recent literature suggests a more prominent role for MAGEA family members in driving bladder tumorigenesis. This review highlights the role of MAGEA proteins, the potential for them to serve as diagnostic or prognostic biomarker(s), and as therapeutic targets for bladder cancer.

Evolution by innovation as a driving force to improve TCR-T therapies

Adoptive cell therapies continually evolve through science-based innovation. Specialized innovations for TCR-T therapies are described here that are embedded in an End-to-End Platform for TCR-T Therapy Development which aims to provide solutions for key unmet patient needs by addressing challenges of TCR-T therapy, including selection of target antigens and suitable T cell receptors, generation of TCR-T therapies that provide long term, durable efficacy and safety and development of efficient and scalable production of patient-specific (personalized) TCR-T therapy for solid tumors. Multiple, combinable, innovative technologies are used in a systematic and sequential manner in the development of TCR-T therapies. One group of technologies encompasses product enhancements that enable TCR-T therapies to be safer, more specific and more effective. The second group of technologies addresses development optimization that supports discovery and development processes for TCR-T therapies to be performed more quickly, with higher quality and greater efficiency. Each module incorporates innovations layered onto basic technologies common to the field of immunology. An active approach of "evolution by innovation" supports the overall goal to develop best-in-class TCR-T therapies for treatment of patients with solid cancer.

A comprehensive review on novel targeted therapy methods and nanotechnology-based gene delivery systems in melanoma

Melanoma, a malignant form of skin cancer, has been swiftly increasing in recent years. Although there have been significant advancements in clinical treatment underlying a well-understanding of melanoma-susceptible genes and the molecular basis of melanoma pathogenesis, the permanency of response to therapy is frequently constrained by the emergence of acquired resistance and systemic toxicity. Conventional therapies, including surgical resection, chemotherapy, radiotherapy, and immunotherapy, have already been used to treat melanoma and are dependent on the cancer stage. Nevertheless, ineffective side effects and the heterogeneity of tumors pose major obstacles to the therapeutic treatment of malignant melanoma through such strategies. In light of this, advanced therapies including nucleic acid therapies (ncRNA, aptamers), suicide gene therapies, and gene therapy using tumor suppressor genes, have lately gained immense attention in the field of cancer treatment. Furthermore, nanomedicine and targeted therapy based on gene editing tools have been applied to the treatment of melanoma as potential cancer treatment approaches nowadays. Indeed, nanovectors enable delivery of the therapeutic agents into the tumor sites by passive or active targeting, improving therapeutic efficiency and minimizing adverse effects. Accordingly, in this review, we summarized the recent findings related to novel targeted therapy methods as well as nanotechnology-based gene systems in melanoma. We also discussed current issues along with potential directions for future research, paving the way for the next-generation of melanoma treatments.

A phenotypic signature that identifies neoantigen-reactive T cells in fresh human lung cancers

A common theme across multiple successful immunotherapies for cancer is the recognition of tumor-specific mutations (neoantigens) by T cells. The rapid discovery of such antigen responses could lead to improved therapies through the adoptive transfer of T cells engineered to express neoantigen-reactive T cell receptors (TCRs). Here, through CITE-seq (cellular indexing of transcriptomes and epitopes by sequencing) and TCR-seq of non-small cell lung cancer (NSCLC) tumor-infiltrating lymphocytes (TILs), we develop a neoantigen-reactive T cell signature based on clonotype frequency and CD39 protein and CXCL13 mRNA expression. Screening of TCRs selected by the signature allows us to identify neoantigen-reactive TCRs with a success rate of 45% for CD8+ and 66% for CD4+ T cells. Because of the small number of samples analyzed (4 patients), generalizability remains to be tested. However, this approach can enable the quick identification of neoantigen-reactive TCRs and expedite the engineering of personalized neoantigen-reactive T cells for therapy.

Immunotherapy for Hepatocellular Carcinoma: Current Limits and Prospects

Although many approaches have been used to treat hepatocellular carcinoma (HCC), the clinical benefits remain limited, particularly for late stage HCC. In recent years, studies have focused on immunotherapy for HCC. Immunotherapies have shown promising clinical outcomes in several types of cancers and potential therapeutic effects for advanced HCC. In this review, we summarize the immune tolerance and immunotherapeutic strategies for HCC as well as the main challenges of current therapeutic approaches. We also present alternative strategies for overcoming these limitations.

Arming Immune Cells for Battle: A Brief Journey through the Advancements of T and NK Cell Immunotherapy

Simple Summary

This review is intended to provide an overview on the history and recent advances of T cell and natural killer (NK) cell-based immunotherapy. While the thymus was discovered as the origin of T cells in the 1960s, and NK cells were first described in 1975, the clinical application of adoptive cell therapies (ACT) only began in the early 1980s with the first lymphokine activated killer (LAK) cell product for the treatment of cancer patients. Over the past decades, further immunotherapies have been developed, including ACT using cytokine-induced killer (CIK) cells, products based on the NK cell line NK-92 as well as specific T and NK cell preparations. Recent advances have successfully improved the effectiveness of T, NK, CIK or NK-92 cells towards tumor-targeting antigens generated by genetic engineering of the immune cells. Herein, we summarize the promising development of ACT over the past decades in the fight against cancer.

Abstract

The promising development of adoptive immunotherapy over the last four decades has revealed numerous therapeutic approaches in which dedicated immune cells are modified and administered to eliminate malignant cells. Starting in the early 1980s, lymphokine activated killer (LAK) cells were the first ex vivo generated NK cell-enriched products utilized for adoptive immunotherapy. Over the past decades, various immunotherapies have been developed, including cytokine-induced killer (CIK) cells, as a peripheral blood mononuclear cells (PBMCs)-based therapeutic product, the adoptive transfer of specific T and NK cell products, and the NK cell line NK-92. In addition to allogeneic NK cells, NK-92 cell products represent a possible “off-the-shelf” therapeutic concept. Recent approaches have successfully enhanced the specificity and cytotoxicity of T, NK, CIK or NK-92 cells towards tumor-specific or associated target antigens generated by genetic engineering of the immune cells, e.g., to express a chimeric antigen receptor (CAR). Here, we will look into the history and recent developments of T and NK cell-based immunotherapy.

Adoptive T cell therapy: Boosting the immune system to fight cancer

Cellular therapies have shown increasing promise as a cancer treatment. Encouraging results against hematologic malignancies are paving the way to move into solid tumors. In this review, we will focus on T-cell therapies starting from tumor infiltrating lymphocytes (TILs) to optimized T-cell receptor-modified (TCR) cells and chimeric antigen receptor-modified T cells (CAR-Ts). We will discuss the positive preclinical and clinical findings of these approaches, along with some of the persisting barriers that need to be overcome to improve outcomes.

Conventional T cell therapies pave the way for novel Treg therapeutics

Approaches to harness the immune system to alleviate disease have become remarkably sophisticated since the crude, yet impressively-effective, attempts using live bacteria in the late 1800s. Recent evidence that engineered T cell therapy can deliver durable results in patients with cancer has spurred frenzied development in the field of T cell therapy. The myriad approaches include an innumerable variety of synthetic transgenes, multiplex gene-editing, and broader application to diseases beyond cancer. In this article, we review the preclinical studies and over a decade of clinical experience with engineered conventional T cells that have paved the way for translating engineered regulatory T cell therapies.

A bicistronic vector backbone for rapid seamless cloning and chimerization of αβT-cell receptor sequences

To facilitate preclinical testing of T-cell receptors (TCRs) derived from tumor-reactive T-cell clones it is necessary to develop convenient and rapid cloning strategies for the generation of TCR expression constructs. Herein, we describe a pDONR™221 vector backbone allowing to generate Gateway™ compatible entry clones encoding optimized bicistronic αβTCR constructs. It harbors P2A-linked TCR constant regions and head-to-head-oriented recognition sites of the Type IIS restriction enzymes BsmBI and BsaI for seamless cloning of the TCRα and TCRβ V(D)J regions, respectively. Additional well-established TCR optimizations were incorporated to enhance TCR functionality. This included replacing of the human αβTCR constant regions with their codon-optimized murine counterparts for chimerization, addition of a second interchain disulfide bond and arrangement of the TCR chains in the order β-P2A-α. We exemplified the utility of our vector backbone by cloning and functional testing of three melanoma-reactive TCRs in primary human T cells.

Fasten the seat belt: Increasing safety of CAR T-cell therapy

After the recent success and approvals of chimeric antigen receptor (CAR) T cells in haematological malignancies, its efficacy is currently evaluated in a broad spectrum of tumor entities including melanoma. However, severe and potentially life-threatening side effects like cytokine release syndrome, neurologic toxicities, and the competing risk of morbidity and mortality from the treatment itself are still a major limiting factor in the current CAR T-cell landscape. In addition, especially in solid tumors, the lack of ideal target antigens to avoid on-target/off-tumor toxicities also restricts its use. While various groups are working on strategies to boost CAR T-cell efficacy, mechanisms to increase engineered T-cell safety should not move out of focus. Thus, the aim of this article is to summarize and to discuss current and potential future strategies and mechanisms to increase CAR T-cell safety in order to enable the wide use of this promising approach in melanoma and other tumor entities.

Targeting cancers through TCR-peptide/MHC interactions

Adoptive T cell therapy has achieved dramatic success in a clinic, and the Food and Drug Administration approved two chimeric antigen receptor-engineered T cell (CAR-T) therapies that target hematological cancers in 2018. A significant issue faced by CAR-T therapies is the lack of tumor-specific biomarkers on the surfaces of solid tumor cells, which hampers the application of CAR-T therapies to solid tumors. Intracellular tumor-related antigens can be presented as peptides in the major histocompatibility complex (MHC) on the cell surface, which interact with the T cell receptors (TCR) on antigen-specific T cells to stimulate an anti-tumor response. Multiple immunotherapy strategies have been developed to eradicate tumor cells through targeting the TCR-peptide/MHC interactions. Here, we summarize the current status of TCR-based immunotherapy strategies, with particular focus on the TCR structure, activated signaling pathways, the effects and toxicity associated with TCR-based therapies in clinical trials, preclinical studies examining immune-mobilizing monoclonal TCRs against cancer (ImmTACs), and TCR-fusion molecules. We propose several TCR-based therapeutic strategies to achieve optimal clinical responses without the induction of autoimmune diseases.

Single variable domains from the T cell receptor β chain function as mono- and bifunctional CARs and TCRs

Cell therapy using T cell receptors (TCRs) and chimeric antigen receptors (CARs) represents a new wave of immunotherapies garnering considerable attention and investment. Further progress in this area of medicine depends in part on improving the functional capabilities of the engineered components, while maintaining the overall size of recombinant constructs to ensure their compatibility with existing gene delivery vehicles. We describe a single-variable-domain TCR (svd TCR) that utilizes only the variable domain of the β chain (Vβ). This Vβ module not only works in TCR and CAR formats, but also can be used to create single-chain bispecific CARs and TCRs. Comparison of individual ligand-binding Vβ domains in different formats suggests that the lone Vβ sequence controls the sensitivity and a major part of the specificity of the CAR or TCR construct, regardless of signaling format, in Jurkat and primary T cells.

Cell transfer-based immunotherapies in cancer: A review

In cell transfer therapy (CTT), immune cells such as innate immune-derived natural killer cells and dendritic cells as well as acquired immune-related T lymphocytes such as tumor-infiltrating lymphocytes and cytokine-activated or genetically modified peripheral blood T cells are used in the management of cancer. These therapies are increasingly becoming the most used treatment modality in cancer after tumor resection, chemotherapy, and radiotherapy. In adoptive cell transfer, the lymphocytes isolated from either a donor or the patient are modified ex vivo and reinfused to target malignant cells. Transferring in vitro-manipulated immune cells produces a continuous antitumor immune response. In this review, we evaluate the recent advances in CTT for the management of various malignancies.

Advances in Engineering Cells for Cancer Immunotherapy

Cancer immunotherapy aims to utilize the host immune system to kill cancer cells. Recent representative immunotherapies include T-cell transfer therapies, such as chimeric antigen receptor T cell therapy, antibody-based immunomodulator therapies, such as immune checkpoint blockade therapy, and cytokine therapies. Recently developed therapies leveraging engineered cells for immunotherapy against cancers have been reported to enhance antitumor efficacy while reducing side effects. Such therapies range from biologically, chemically and physically -engineered cells to bioinspired and biomimetic nanomedicines. In this review, advances of engineering cells for cancer immunotherapy are summarized, and prospects of this field are discussed.

Gene editing: Towards the third generation of adoptive T-cell transfer therapies

First-generation adoptive T-cell transfer (ACT) administering tumor-infiltrating lymphocytes (TILs), and second-generation ACT using autologous T cells genetically modified to express tumor-specific T-cell receptors (TCRs) or chimeric antigen receptors (CARs) have both shown promise for the treatment of several cancers, including melanoma, leukemia and lymphoma. However, these treatments require labor-intensive manufacturing of the cell product for each patient, frequently utilize lentiviral or retroviral vectors to genetically modify the T cells, and have limited antitumor efficacy in solid tumors. Gene editing is revolutionizing the field of gene therapy, and ACT is at the forefront of this revolution. Gene-editing technologies can be used to re-engineer the phenotype of T cells to increase their antitumor potency, to generate off-the-shelf ACT products, and to replace endogenous TCRs with tumor-specific TCRs or CARs using homology-directed repair (HDR) donor templates. Adeno-associated viral vectors or linear DNA have been used as HDR donor templates. Of note, non-viral delivery substantially reduces the time required to generate clinical-grade reagents for manufacture of T-cell products—a critical step for the translation of personalized T-cell therapies. These technological advances in the field using gene editing open the door to the third generation of ACT therapies.

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CRISPR-Cas9 allows the generation of tumor-specific T cells for adoptive T-cell transfer (ACT).

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Gene editing allows generation of off-the-shelf ACT products.

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Gene editing can tailor T-cell phenotype and increase antitumor potency.

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Non-viral gene editing is a requirement for personalized ACT.

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Personalized third-generation ACT: gene-edited neoantigen-specific T cells.

Unique Neoantigens Arise from Somatic Mutations in Patients with Gastrointestinal Cancers

Immunotherapies can mediate regression of human tumors with high mutation rates, but responses are rarely observed in patients with common epithelial cancers. This raises the question of whether patients with these common cancers harbor T lymphocytes that recognize mutant proteins expressed by autologous tumors that may represent ideal targets for immunotherapy. Using high-throughput immunologic screening of mutant gene products identified via whole-exome sequencing, we identified neoantigen-reactive tumor-infiltrating lymphocytes (TIL) from 62 of 75 (83%) patients with common gastrointestinal cancers. In total, 124 neoantigen-reactive TIL populations were identified, and all but one of the neoantigenic determinants were unique. The results of in vitro T-cell recognition assays demonstrated that 1.6% of the gene products encoded by somatic nonsynonymous mutations were immunogenic. These findings demonstrate that the majority of common epithelial cancers elicit immune recognition and open possibilities for cell-based immunotherapies for patients bearing these cancers. SIGNIFICANCE: TILs cultured from 62 of 75 (83%) patients with gastrointestinal cancers recognized neoantigens encoded by 1.6% of somatic mutations expressed by autologous tumor cells, and 99% of the neoantigenic determinants appeared to be unique and not shared between patients.This article is highlighted in the In This Issue feature, p. 983.

Immunotherapy: Current Status and Future Perspectives

Hepatocellular carcinoma (HCC) has an increasing incidence and dismal prognosis, with few systemic treatments approved, including several small molecule tyrosine kinase inhibitors. The application of immune checkpoint inhibitors (ICIs) to HCC has resulted in durable activity, and further evaluation is ongoing. In this review, we discuss the immunologic principles and the mechanism of action of the ICIs and present the relevant clinical data. Furthermore, we provide an overview of the current and emerging immunotherapeutic approaches for HCC, such as combination treatments, vaccines, and cellular therapies.

Functional genomics: paving the way for more successful cancer immunotherapy

Immunotherapies have revolutionized cancer treatment. Immunotherapy is effective for the treatment of a wide range of cancer types and can mediate complete and durable tumor regression. Nonetheless, the field still faces many significant challenges, such as the need for personalized therapeutic strategies and better biomarkers, the difficulty of selecting the right combination therapy, and resistance to currently available immunotherapies. Both cancer and host immunity comprise significantly diverse and complex ecosystems, making immunogenomics an ideal field for functional genomics analysis. In this review, we describe the cancer-immunity cycle, how cancer cells manage to evade immune attack and the current hurdles in the path of cancer immunotherapy. Then, we discuss how functional genomics approaches can pave the way for more successful cancer immunotherapies.

T-cell receptor gene-modified cells: past promises, present methodologies and future challenges

Immunotherapy constitutes an exciting and rapidly evolving field, and the demonstration that genetically modified T-cell receptors (TCRs) can be used to produce T-lymphocyte populations of desired specificity offers new opportunities for antigen-specific T-cell therapy. Overall, TCR-modified T cells have the ability to target a wide variety of self and non-self targets through the normal biology of a T cell. Although major histocompatibility complex (MHC)-restricted and dependent on co-receptors, genetically engineered TCRs still present a number of characteristics that ensure they are an important alternative strategy to chimeric antigen receptors (CARs), and high-affinity TCRs can now be successfully engineered with the potential to enhance therapeutic efficacy while minimizing adverse events. This review will focus on the main characteristics of TCR gene-modified cells, their potential clinical application and promise to the field of adoptive cell transfer (ACT), basic manufacturing procedures and characterization protocols and overall challenges that need to be overcome so that redirection of TCR specificity may be successfully translated into clinical practice, beyond early-phase clinical trials.

Current and Emerging Targets in Immunotherapy for Osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. Although outcomes of patients with osteosarcoma have improved since the introduction of chemotherapy, outcomes of metastatic or unresectable osteosarcomas are still unsatisfactory. To improve osteosarcoma outcomes, the development of novel systemic therapies for osteosarcoma is needed. Since the 1880s, various immunotherapies have been utilized in patients with osteosarcoma and some patients have shown response to the treatment. Based on recent studies about the role of the immune system in malignancies, immunotherapies including immune modulators such as interleukin-2 and muramyl tripeptide, dendritic cells, immune checkpoint inhibitors, and engineered T cells have been utilized in patients with malignancies. Although there are limited reports of immunotherapies for osteosarcoma, immunotherapy is thought to be a promising treatment option for treating osteosarcomas. In this review, an overview of various immunotherapies for osteosarcoma is provided and their potential as adjuvant therapies is discussed.

Promising immunotherapy: Highlighting cytokine-induced killer cells

For many years, cancer therapy has appeared to be a challenging issue for researchers and physicians. By the introduction of novel methods in immunotherapy, the prospect of cancer therapy even more explained than before. Cytokine-induced killer (CIK) cell-based immunotherapy demonstrated to have potentiality in improving clinical outcomes and relieving major side effects of standard treatment options. In addition, given the distinctive features such as high safety, low toxicity effects on healthy cells, numerous clinical trials conducted on CIK cells. Due to the shortcomings that observed in CIK cell immunotherapy alone, arising a tendency to make modifications (combined modality therapy or combination therapy) including the addition of various types of cytokines, genetic engineering, combination with immune checkpoints, and so on. In this review, we have tried to bring forth the latest immunotherapy methods and their overview. We have discussed the combination therapies with CIK cells and the conducted clinical trials. This helps the future studies to use integrated therapies with CIK cells as a promising treatment of many types of cancers.

Current frontline approaches in the management of hepatocellular carcinoma: the evolving role of immunotherapy

Hepatocellular carcinoma (HCC) is a major cause of cancer-associated mortality worldwide and is expected to rise. Patients with early-stage disease may have a good prognosis with a 5-year survival rate of greater than 70%. However, the majority of patients are diagnosed with late-stage disease with a dismal overall survival rate of less than 16%. Therefore, there is a great need for advances in the treatment of advanced HCC, which for approximately the past decade, has been sorafenib. Immunotherapy is an evolving cancer treatment and has shown promise in treating patients with advanced HCC. In this review, we discuss the current standard of care for advanced HCC and then discuss the evolving role of immunotherapies.

Isolation of T-Cell Receptors Specifically Reactive with Mutated Tumor-Associated Antigens from Tumor-Infiltrating Lymphocytes Based on CD137 Expression

Purpose: The adoptive transfer of lymphocytes genetically modified to express tumor reactive T-cell receptors (TCR) can mediate tumor regression. Some tumor-infiltrating lymphocytes (TIL) recognize somatic mutations expressed only in the patient's tumors, and evidence suggests that clinically effective TILs target tumor-specific neoantigens. Here we attempted to isolate neoantigen-reactive TCRs as a prelude to the treatment of patients with autologous T cells genetically modified to express such TCRs.Experimental Design: Mutations expressed by tumors were identified using whole-exome and RNA sequencing. Tandem minigene (TMG) constructs encoding 12-24 mutated gene products were synthesized, each encoding the mutated amino acid flanked by 12 amino acids of the normal protein sequence. TILs were cultured with autologous dendritic cells (DC) transfected with in vitro transcribed (IVT) mRNAs encoding TMGs and were evaluated for IFNγ secretion and CD137 expression. Neoantigen-reactive T cells were enriched from TILs by sorting for CD137⁺ CD8⁺ T cells and expanded in vitro Dominant TCR α and β chains were identified in the enriched populations using a combination of 5' rapid amplification of cDNA ends, deep sequencing of genomic DNA, PairSeq analysis, and single-cell RT-PCR analysis. Human PBL retrovirally transduced to express the TCRs were evaluated for recognition of relevant neoantigens.Results: We identified 27 TCRs from 6 patients that recognized 14 neoantigens expressed by autologous tumor cells.Conclusions: This strategy provides the means to generate T cells expressing neoantigen-reactive TCRs for use in future adoptive cell transfer immunotherapy trials for patients with cancer. Clin Cancer Res; 23(10); 2491-505. ©2016 AACR.

Adoptive Transfer of Engineered Rhesus Simian Immunodeficiency Virus-Specific CD8+ T Cells Reduces the Number of Transmitted/Founder Viruses Established in Rhesus Macaques

AIDS virus infections are rarely controlled by cell-mediated immunity, in part due to viral immune evasion and immunodeficiency resulting from CD4+ T-cell infection. One likely aspect of this failure is that antiviral cellular immune responses are either absent or present at low levels during the initial establishment of infection. To test whether an extensive, timely, and effective response could reduce the establishment of infection from a high-dose inoculum, we adoptively transferred large numbers of T cells that were molecularly engineered with anti-simian immunodeficiency virus (anti-SIV) activity into rhesus macaques 3 days following an intrarectal SIV inoculation. To measure in vivo antiviral activity, we assessed the number of viruses transmitted using SIVmac239X, a molecularly tagged viral stock containing 10 genotypic variants, at a dose calculated to transmit 12 founder viruses. Single-genome sequencing of plasma virus revealed that the two animals receiving T cells expressing SIV-specific T-cell receptors (TCRs) had significantly fewer viral genotypes than the two control animals receiving non-SIV-specific T cells (means of 4.0 versus 7.5 transmitted viral genotypes; P = 0.044). Accounting for the likelihood of transmission of multiple viruses of a particular genotype, the calculated means of the total number of founder viruses transmitted were 4.5 and 14.5 in the experimental and control groups, respectively (P = 0.021). Thus, a large antiviral T-cell response timed with virus exposure can limit viral transmission. The presence of strong, preexisting T-cell responses, including those induced by vaccines, might help prevent the establishment of infection at the lower-exposure doses in humans that typically transmit only a single virus.

IMPORTANCE

The establishment of AIDS virus infection in an individual is essentially a race between the spreading virus and host immune defenses. Cell-mediated immune responses induced by infection or vaccination are important contributors in limiting viral replication. However, in human immunodeficiency virus (HIV)/SIV infection, the virus usually wins the race, irreversibly crippling the immune system before an effective cellular immune response is developed and active. We found that providing an accelerated response by adoptively transferring large numbers of antiviral T cells shortly after a high-dose mucosal inoculation, while not preventing infection altogether, limited the number of individual viruses transmitted. Thus, the presence of strong, preexisting T-cell responses, including those induced by vaccines, might prevent infection in humans, where the virus exposure is considerably lower.

A Functionally Superior Second-Generation Vector Expressing an Aurora Kinase-A-Specific T-Cell Receptor for Anti-Leukaemia Adoptive Immunotherapy

Aurora Kinase A is a cancer-associated protein normally involved in the regulation of mitosis. Being over-expressed in a range of cancers, it is a suitable target for cell-based immunotherapy. Gene transfer of T-cell receptor sequences cognisant of HLA-A*0201-restricted Aurora Kinase A antigen has previously been shown to transfer specific immunoreactivity against the target peptide in a Human Lymphocyte Antigen-restricted manner. While T cell receptor gene-transfer has great potential in overcoming the difficulties of isolating and expanding tumour-reactive lymphocytes from a patient’s own cells, one hurdle is potential mispairing and competition between exogenous and endogenous T cell receptor chains. We have used a retroviral vector design bearing a short-interfering RNA that downregulates endogenous T cell receptor chains, without affecting expression of the transgenic T cell receptor sequences. The T cell receptor expression cassette also includes a 2A self-cleaving peptide, resulting in equimolar expression of the T cell receptor alpha and beta chains, further enhancing formation of the desired T cell receptor. Via a simple, modular cloning method, we have cloned the alpha and beta chains of the anti-Aurora Kinase A-reactive T cell receptor into this ‘siTCR’ vector. We then compared the activity of this vector against the original, ‘conventional’ vector across a panel of assays. T cell receptors expressed from the siTCR-vector retained the cytotoxic functionality of the original vector, with evidence of reduced off-target reactivity. The rate of expression of correctly-formed T cell receptors was superior using the siTCR design, and this was achieved at lower vector copy numbers. Maintaining T cell receptor efficacy with a reduced vector copy number reduces the risk of genotoxicity. The siTCR design also reduces the risk of mispairing and cross-reactivity, while increasing the functional titre. Such improvements in the safety of T cell receptor gene-transfer will be crucial for clinical applications of this technology.

Proteasomes generate spliced epitopes by two different mechanisms and as efficiently as non-spliced epitopes

Proteasome-catalyzed peptide splicing represents an additional catalytic activity of proteasomes contributing to the pool of MHC-class I-presented epitopes. We here biochemically and functionally characterized a new melanoma gp100 derived spliced epitope. We demonstrate that the gp100^mel_{47–52/40–42} antigenic peptide is generated in vitro and in cellulo by a not yet described proteasomal condensation reaction. gp100^mel_{47–52/40–42} generation is enhanced in the presence of the β5i/LMP7 proteasome-subunit and elicits a peptide-specific CD8⁺ T cell response. Importantly, we demonstrate that different gp100^mel-derived spliced epitopes are generated and presented to CD8⁺ T cells with efficacies comparable to non-spliced canonical tumor epitopes and that gp100^mel-derived spliced epitopes trigger activation of CD8⁺ T cells found in peripheral blood of half of the melanoma patients tested. Our data suggest that both transpeptidation and condensation reactions contribute to the frequent generation of spliced epitopes also in vivo and that their immune relevance may be comparable to non-spliced epitopes.

To affinity and beyond: harnessing the T cell receptor for cancer immunotherapy

T cell adoptive therapies for immune-mediated regression of cancers have attracted a great deal of recent attention. Clinical results are glamorous, yet much remains to be uncovered behind the basic science that allows us to engineer T cells and T cell receptors (TCRs) for clinical use. We discuss the development of TCRs for therapeutic use in the context of thymic selection toward central tolerance and we review therapies based on tumor infiltrating lymphocytes (TILs), endogenous antigen specific TCRs, and engineered TCRs. Further we discuss the development of low and high affinity TCRs and the extent to which each challenges central tolerance. Current results suggest that adaptation of TCR engineering of moderate affinity TCRs coupled with co-regulatory and stimulatory molecules may be the safest and most efficacious road for TCR development aimed at tumor abolition.

Knockdown of T-bet expression in Mart-127-35 -specific T-cell-receptor-engineered human CD4(+) CD25(-) and CD8(+) T cells attenuates effector function

Gene transfer to create tumour epitope-specific cytolytic T cells for adoptive immunotherapy of cancer remains an area of active inquiry. When the Mart-127-35 -specific DMF5 T-cell receptor (TCR) is transferred into peripheral human CD4(+) T cells, the reprogrammed cells exhibit a T helper type 1 (Th1) phenotype with significant multifactorial effector capabilities. The T-bet transcription factor plays an important role in determination of the Th1 differentiation pathway. To gain a deeper understanding of how T-bet controls the outcome of human T-cell reprogramming by gene transfer, we developed a system for examining the effects of short hairpin RNA-mediated T-bet gene knockdown in sorted cell populations uniformly expressing the knockdown construct. In this system, using activated peripheral human CD4(+)  CD25(-) and CD8(+) T cells, T-bet knockdown led to attenuation of the interferon-γ response to both antigen-specific and non-specific TCR stimulation. The interleukin-2 (IL-2) antigen-specific response was not attenuated by T-bet knockdown. Also, in TCR-reprogrammed CD8(+) cells, the cytolytic effector response was attenuated by T-bet knockdown. T-bet knockdown did not cause redirection into a Th2 differentiation pathway, and no increased IL-4, IL-10, or IL-17 response was detected in this system. These results indicate that T-bet expression is required for maintenance of the CD4(+)  CD25(-) and CD8(+) effector phenotypes in TCR-reprogrammed human T cells. They also suggest that the activation protocol necessary for transduction with retrovectors and lentivectors may commit the reprogrammed cells to the Th1 phenotype, which cannot be altered by T-bet knockdown but that there is, nevertheless, a continuous requirement of T-bet expression for interferon-γ gene activation.

Generation of β cell-specific human cytotoxic T cells by lentiviral transduction and their survival in immunodeficient human leucocyte antigen-transgenic mice

Several β cell antigens recognized by T cells in the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D) are also T cell targets in the human disease. While numerous antigen-specific therapies prevent diabetes in NOD mice, successful translation of rodent findings to patients has been difficult. A human leucocyte antigen (HLA)-transgenic mouse model incorporating human β cell-specific T cells might provide a better platform for evaluating antigen-specific therapies. The ability to study such T cells is limited by their low frequency in peripheral blood and the difficulty in obtaining islet-infiltrating T cells from patients. We have worked to overcome this limitation by using lentiviral transduction to 'reprogram' primary human CD8 T cells to express three T cell receptors (TCRs) specific for a peptide derived from the β cell antigen islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP265-273 ) and recognized in the context of the human class I major histocompatibility complex (MHC) molecule HLA-A2. The TCRs bound peptide/MHC multimers with a range of avidities, but all bound with at least 10-fold lower avidity than the anti-viral TCR used for comparison. One exhibited antigenic recognition promiscuity. The β cell-specific human CD8 T cells generated by lentiviral transduction with one of the TCRs released interferon (IFN)-γ in response to antigen and exhibited cytotoxic activity against peptide-pulsed target cells. The cells engrafted in HLA-A2-transgenic NOD-scid IL2rγ(null) mice and could be detected in the blood, spleen and pancreas up to 5 weeks post-transfer, suggesting the utility of this approach for the evaluation of T cell-modulatory therapies for T1D and other T cell-mediated autoimmune diseases.

The New Era of Cancer Immunotherapy: Manipulating T-Cell Activity to Overcome Malignancy

Using the immune system to control cancer has been investigated for over a century. Yet it is only over the last several years that therapeutic agents acting directly on the immune system have demonstrated improved overall survival for cancer patients in phase III clinical trials. Furthermore, it appears that some patients treated with such agents have been cured of metastatic cancer. This has led to increased interest and acceleration in the rate of progress in cancer immunotherapy. Most of the current immunotherapeutic success in cancer treatment is based on the use of immune-modulating antibodies targeting critical checkpoints (CTLA-4 and PD-1/PD-L1). Several other immune-modulating molecules targeting inhibitory or stimulatory pathways are being developed. The combined use of these medicines is the subject of intense investigation and holds important promise. Combination regimens include those that incorporate targeted therapies that act on growth signaling pathways, as well as standard chemotherapy and radiation therapy. In fact, these standard therapies have intrinsic immune-modulating properties that can support antitumor immunity. In the years ahead, adoptive T-cell therapy will also be an important part of treatment for some cancer patients. Other areas which are regaining interest are the use of oncolytic viruses that immunize patients against their own tumors and the use of vaccines against tumor antigens. Immunotherapy has demonstrated unprecedented durability in controlling multiple types of cancer and we expect its use to continue expanding rapidly.

Adoptive cell therapy for sarcoma

Current therapy for sarcomas, though effective in treating local disease, is often ineffective for patients with recurrent or metastatic disease. To improve outcomes, novel approaches are needed and cell therapy has the potential to meet this need since it does not rely on the cytotoxic mechanisms of conventional therapies. The recent successes of T-cell therapies for hematological malignancies have led to renewed interest in exploring cell therapies for solid tumors such as sarcomas. In this review, we will discuss current cell therapies for sarcoma with special emphasis on genetic approaches to improve the effector function of adoptively transferred cells.

Human MHC Class I-restricted high avidity CD4+ T cells generated by co-transfer of TCR and CD8 mediate efficient tumor rejection in vivo

In this study, we generated human MHC Class I-restricted CD4⁺ T cells specific for Epstein-Barr virus (EBV) and cytomegalovirus (CMV), two herpesviridae associated with lymphoma, nasopharyngeal carcinoma and medulloblastoma, respectively. Retroviral transfer of virus-specific, HLA-A2-restricted TCR-coding genes generated CD4⁺ T cells that recognized HLA-A2/peptide multimers and produced cytokines when stimulated with MHC Class II-deficient cells presenting the relevant viral peptides in the context of HLA-A2. Peptide titration revealed that CD4⁺ T cells had a 10-fold lower avidity than CD8⁺ T cells expressing the same TCR. The impaired avidity of CD4⁺ T cells was corrected by simultaneously transferring TCR- and CD8-coding genes. The CD8 co-receptor did not alter the cytokine signature of CD4⁺ T cells, which remained distinct from that of CD8⁺ T cells. Using the xenogeneic NOD/SCID mouse model, we demonstrated that human CD4⁺ T cells expressing a specific TCR and CD8 can confer efficient protection against the growth of tumors expressing the EBV or CMV antigens recognized by the TCR. In summary, we describe a robust approach for generating therapeutic CD4⁺ T cells capable of providing MHC Class I-restricted immunity against MHC Class II-negative tumors in vivo.

Adoptive immunotherapy for cancer

Recent clinical success has underscored the potential for immunotherapy based on the adoptive cell transfer (ACT) of engineered T lymphocytes to mediate dramatic, potent, and durable clinical responses. This success has led to the broader evaluation of engineered T-lymphocyte-based adoptive cell therapy to treat a broad range of malignancies. In this review, we summarize concepts, successes, and challenges for the broader development of this promising field, focusing principally on lessons gleaned from immunological principles and clinical thought. We present ACT in the context of integrating T-cell and tumor biology and the broader systemic immune response.

EGFRvIII-specific chimeric antigen receptor T cells migrate to and kill tumor deposits infiltrating the brain parenchyma in an invasive xenograft model of glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and is uniformly lethal. T-cell-based immunotherapy offers a promising platform for treatment given its potential to specifically target tumor tissue while sparing the normal brain. However, the diffuse and infiltrative nature of these tumors in the brain parenchyma may pose an exceptional hurdle to successful immunotherapy in patients. Areas of invasive tumor are thought to reside behind an intact blood brain barrier, isolating them from effective immunosurveillance and thereby predisposing the development of "immunologically silent" tumor peninsulas. Therefore, it remains unclear if adoptively transferred T cells can migrate to and mediate regression in areas of invasive GBM. One barrier has been the lack of a preclinical mouse model that accurately recapitulates the growth patterns of human GBM in vivo. Here, we demonstrate that D-270 MG xenografts exhibit the classical features of GBM and produce the diffuse and invasive tumors seen in patients. Using this model, we designed experiments to assess whether T cells expressing third-generation chimeric antigen receptors (CARs) targeting the tumor-specific mutation of the epidermal growth factor receptor, EGFRvIII, would localize to and treat invasive intracerebral GBM. EGFRvIII-targeted CAR (EGFRvIII+ CAR) T cells demonstrated in vitro EGFRvIII antigen-specific recognition and reactivity to the D-270 MG cell line, which naturally expresses EGFRvIII. Moreover, when administered systemically, EGFRvIII+ CAR T cells localized to areas of invasive tumor, suppressed tumor growth, and enhanced survival of mice with established intracranial D-270 MG tumors. Together, these data demonstrate that systemically administered T cells are capable of migrating to the invasive edges of GBM to mediate antitumor efficacy and tumor regression.

Advances and Prospects in Cancer Immunotherapy

Cancer immunotherapy is a promising and effective treatment modality for patients with cancers. Cytokine, anticytokine, and antibody therapies appear to be effective in treating various forms of cancer. The human papillomavirus vaccine is protective for cervical cancer, and this discovery has paved the way to the development of cancer vaccines for other forms of virus-associated cancers such as liver cancer and Merkel cell carcinoma. Clinical trials have demonstrated that adoptive cell therapy using tumor-infiltrating lymphocytes can induce tumor regression in approximately 75% of metastatic melanoma patients, suggesting the possibility of using similar technique to effectively treat breast, lung, and renal cancers in the near future. Besides, genetically engineered T cells transduced with genes encoding specific T cell receptors and chimeric antigen receptors have been shown effective in the treatment of cancer patients. These studies suggest that combination therapies are superior choices in cancer immunotherapy for patients.

Cell transfer therapy for cancer: past, present, and future

Cell transfer therapy for cancer has made a rapid progress recently and the immunotherapy has been recognized as the fourth anticancer modality after operation, chemotherapy, and radiotherapy. Lymphocytes used for cell transfer therapy include dendritic cells, natural killer (NK) cells, and T lymphocytes such as tumor-infiltrating lymphocytes (TILs) and cytotoxic T lymphocytes (CTLs). In vitro activated or engineered immune cells can traffic to cancer tissues to elicit persistent antitumor immune response which is very important especially after immunosuppressive treatments such as chemotherapy. In this review, we overviewed recent advances in the exploration of dendritic cells, NK cells, and T cells for the treatment of human cancer cells.

Clinical Implications of T Cell Receptor Repertoire Analysis after Allogeneic Stem Cell Transplantation

Stem cell transplantation (SCT) constitutes a major challenge to the immune system. Long-term impairment of immunity against various common infectious stimuli leads to increased susceptibility to infectious diseases; in contrast, an immune response against the recipient may cause the devastating graft-versus-host disease (GvHD). Recovery of the immune system (both qualitative and quantitative) after SCT is perhaps the most important factor in determining the clinical outcome. Consequently, immune reconstitution has been extensively studied using different approaches, including quantitative analysis of immune cells as well as their phenotypic characterization. Analysis of diversity and clonality is an important tool in determining competence of the immune system, assuming that a broad diversity assures efficient response to different stimuli and clonal dominance reflects ongoing, potentially relevant immune responses. Detailed analysis of the immune repertoire through the flow cytometric and molecular study of the T cell receptor repertoire has been applied to gain quantitative and qualitative insights about the T cell immune competence and responsiveness. After SCT, a contraction of the T cell pool and a reduction in T cell receptor diversity is clearly associated with clinical immunodeficiency. Reconstitution of the immune system is often characterized by dominance of oligoclonal T cell populations, reflecting specific antigen-driven immune responses. Detailed characterization of T lymphocytes by T cell receptor analysis is possible, and may lead to the identification of individual clones involved in specific immune reactions, such as alloresponses in GvHD, the closely related graft-versus-leukemia effect and opportunistic viral agents such as CMV or EBV.

An Altered gp100 Peptide Ligand with Decreased Binding by TCR and CD8α Dissects T Cell Cytotoxicity from Production of Cytokines and Activation of NFAT

Altered peptide ligands (APLs) provide useful tools to study T cell activation and potentially direct immune responses to improve treatment of cancer patients. To better understand and exploit APLs, we studied the relationship between APLs and T cell function in more detail. Here, we tested a broad panel of gp100_280–288 APLs with respect to T cell cytotoxicity, production of cytokines, and activation of Nuclear Factor of Activated T cells (NFAT) by human T cells gene-engineered with a gp100-HLA-A2-specific TCRαβ. We demonstrated that gp100-specific cytotoxicity, production of cytokines, and activation of NFAT were not affected by APLs with single amino acid substitutions, except for an APL with an amino acid substitution at position 3 (APL A3), which did not elicit any T cell response. A gp100 peptide with a double amino acid mutation (APL S4S6) elicited T cell cytotoxicity and production of IFNγ, and to a lesser extent TNFα, IL-4, and IL-5, but not production of IL-2 and IL-10, or activation of NFAT. Notably, T cell receptor (TCR)-mediated functions showed decreases in sensitivities for S4S6 versus gp100 wild-type (wt) peptide, which were minor for cytotoxicity but at least a 1000-fold more prominent for the production of cytokines. TCR-engineered T cells did not bind A3-HLA-A2, but did bind S4S6-HLA-A2 although to a lowered extent compared to wt peptide-HLA-A2. Moreover, S4S6-induced T cell function demonstrated an enhanced dependency on CD8α. Taken together, most gp100 APLs functioned as agonists, but A3 and S4S6 peptides acted as a null ligand and partial agonist, respectively. Our results further suggest that TCR-mediated cytotoxicity can be dissected from production of cytokines and activation of NFAT, and that the agonist potential of peptide mutants relates to the extent of binding by TCR and CD8α. These findings may facilitate the design of APLs to advance the study of T cell activation and their use for therapeutic applications.

Gene-engineered T cells for cancer therapy

T cells have the capacity to eradicate diseased cells, but tumours present considerable challenges that render T cells ineffectual. Cancer cells often make themselves almost 'invisible' to the immune system, and they sculpt a microenvironment that suppresses T cell activity, survival and migration. Genetic engineering of T cells can be used therapeutically to overcome these challenges. T cells can be taken from the blood of cancer patients and then modified with genes encoding receptors that recognize cancer-specific antigens. Additional genes can be used to enable resistance to immunosuppression, to extend survival and to facilitate the penetration of engineered T cells into tumours. Using genetic modification, highly active, self-propagating 'slayers' of cancer cells can be generated.

TCR-ligand koff rate correlates with the protective capacity of antigen-specific CD8+ T cells for adoptive transfer

Adoptive immunotherapy is a promising therapeutic approach for the treatment of chronic infections and cancer. T cells within a certain range of high avidity for their cognate ligand are believed to be most effective. T cell receptor (TCR) transfer experiments indicate that a major part of avidity is hardwired within the structure of the TCR. Unfortunately, rapid measurement of structural avidity of TCRs is difficult on living T cells. We developed a technology where dissociation (koff rate) of truly monomeric peptide-major histocompatibility complex (pMHC) molecules bound to surface-expressed TCRs can be monitored by real-time microscopy in a highly reliable manner. A first evaluation of this method on distinct human cytomegalovirus (CMV)-specific T cell populations revealed unexpected differences in the koff rates. CMV-specific T cells are currently being evaluated in clinical trials for efficacy in adoptive immunotherapy; therefore, determination of koff rates could guide selection of the most effective donor cells. Indeed, in two different murine infection models, we demonstrate that T cell populations with lower koff rates confer significantly better protection than populations with fast koff rates. These data indicate that koff rate measurements can improve the predictability of adoptive immunotherapy and provide diagnostic information on the in vivo quality of T cells.

Engineering human T cells for resistance to methotrexate and mycophenolate mofetil as an in vivo cell selection strategy

Gene transfer and drug selection systems that enforce ongoing transgene expression in vitro and in vivo which are compatible with human pharmaceutical drugs are currently underdeveloped. Here, we report on the utility of incorporating human enzyme muteins that confer resistance to the lymphotoxic/immunosuppressive drugs methotrexate (MTX) and mycophenolate mofetil (MMF) in a multicistronic lentiviral vector for in vivo T lymphocyte selection. We found that co-expression of human dihydrofolate reductase (DHFR(FS); L22F, F31S) and inosine monophosphate dehydrogenase II (IMPDH2(IY); T333I, S351Y) conferred T cell resistance to the cytocidal and anti-proliferative effects of these drugs at concentrations that can be achieved clinically (up to 0.1 µM MTX and 1.0 µM MPA). Furthermore, using a immunodeficient mouse model that supports the engraftment of central memory derived human T cells, in vivo selection studies demonstrate that huEGFRt(+)DHFR(FS+)IMPDH2(IY+) T cells could be enriched following adoptive transfer either by systemic administration of MTX alone (4.4 -fold), MMF alone (2.9-fold), or combined MTX and MMF (4.9-fold). These findings demonstrate the utility of both DHFR(FS)/MTX and IMPDH2(IY)/MMF for in vivo selection of lentivirally transduced human T cells. Vectors incorporating these muteins in combination with other therapeutic transgenes may facilitate the selective engraftment of therapeutically active cells in recipients.

Characterization of human T lymphocytes engineered to express interleukin-15 and herpes simplex virus-thymidine kinase

INTRODUCTION

Preclinical studies have demonstrated that tumor-reactive T cells expressing the interleukin (IL)-15 transgene had enhanced activity. Gene therapy strategies using IL-15 should include a safety mechanism in anticipation of possible adverse effects because IL-15 overexpression has been implicated in autoimmune disorders and may be involved in the pathogenesis of some leukemias. We developed a retroviral vector carrying both IL-15 and the herpes simplex virus-thymidine kinase (HSV-TK) suicide gene and characterized its application in the transduction of human T lymphocytes.

METHODS

A retroviral vector carrying IL-15 and HSV-TK genes was optimized for the transduction of human T lymphocytes. IL-15 production was measured by enzyme-linked immunosorbent assay. Thymidine incorporation and cell viability assays were used to assess the efficacy of the HSV-TK suicide gene. Genetically modified tumor-infiltrating lymphocytes (TILs) were assayed for survival after withdrawal from exogenous IL-2. The activity and specificity of retrovirally transduced TILs were assessed using tumor coculture assays.

RESULTS

Human T cells transduced with the IL-15 HSV-TK vector exhibited thymidine uptake in the absence of exogenous cytokine support and survived in culture for up to 80 d without IL-2. IL-15 HSV-TK-transduced T cells were efficiently killed by ganciclovir at concentrations as low as 0.1 μM. TILs transduced with the IL-15 HSV-TK vector retained specific recognition of HLA-A2+, MART1+ melanomas, even after withdrawal of IL-2.

CONCLUSIONS

Human T lymphocytes genetically modified with the IL-15 HSV-TK retroviral vector retained the ability to recognize tumor antigen while gaining the ability to secrete IL-15 and prolong their own survival. IL-15 HSV-TK-transduced T cells expressed HSV-TK and could be efficiently eliminated by ganciclovir.

Engineering improved T cell receptors using an alanine-scan guided T cell display selection system

T cell receptors (TCRs) on T cells recognize peptide-major histocompatibility complex (pMHC) molecules on the surface of antigen presenting cells and this interaction determines the T cell immune response. Due to negative selection, naturally occurring TCRs bind self (tumor) peptides with low affinity and have a much higher affinity for foreign antigens. This complicates isolation of naturally occurring, high affinity TCRs that mediate more effective tumor rejection for therapeutic purposes. An attractive approach to resolve this issue is to engineer high affinity TCRs in vitro using phage, yeast or mammalian TCR display systems. A caveat of these systems is that they rely on a large library by random mutagenesis due to the lack of knowledge regarding the specific interactions between the TCR and pMHC. We have focused on the mammalian retroviral display system because it uniquely allows for direct comparison of TCR-pMHC-binding properties with T-cell activation outcomes. Through an alanine-scanning approach, we are able to quickly map the key amino acid residues directly involved in TCR-pMHC interactions thereby significantly reducing the library size. Using this method, we demonstrate that for a self-antigen-specific human TCR (R6C12) the key residues for pMHC binding are located in the CDR3β region. This information was used as a basis for designing an efficacious TCR CDR3α library that allowed for selection of TCRs with higher avidity than the wild-type as evaluated through binding and activation experiments. This is a direct approach to target specific TCR residues in TCR library design to efficiently engineer high avidity TCRs that may potentially be used to enhance adoptive immunotherapy treatments.

Genetically engineered T cells for the treatment of cancer

T-cell immunotherapy is a promising approach to treat disseminated cancer. However, it has been limited by the ability to isolate and expand T cells restricted to tumour-associated antigens. Using ex vivo gene transfer, T cells from patients can be genetically engineered to express a novel T cell receptor or chimeric antigen receptor to specifically recognize a tumour-associated antigen and thereby selectively kill tumour cells. Indeed, genetically engineered T cells have recently been successfully used for cancer treatment in a small number of patients. Here we review the recent progress in the field, and summarize the challenges that lie ahead and the strategies being used to overcome them.

Adoptive immunotherapy of advanced melanoma

Adoptive cell therapy (ACT) has emerged as an effective therapy for patients with metastatic melanoma. Since the first introduction of the protocol in 1988 [1], major improvements have been achieved with response rates of 40%-72% among patients who were resistant to previous treatment lines. Both cell product and conditioning regimen are major determinants of treatment efficacy; therefore, developing ACT protocols explore diverse ways to establish autologous intra-tumoral lymphocyte cultures or peripheral effector cells as well as different lymphodepleting regimens. While a proof of feasibility and a proof of concept had been established with previous published results, ACT will need to move beyond single-center experiences, to confirmatory, multi-center studies. If ACT is to move into widespread practice, it will be necessary to develop reproducible high quality cell production methods and accepted lymphodepleting regimen. Two new drugs, ipilimumab (Yervoy, Bristol-Myers Squibb) and vemurafenib (Zelboraf, Roche), were approved in 2011 for the treatment of metastatic melanoma based on positive phase III trials. Both drugs show a clear overall survival benefit, so the timing of when to use ACT will need to be carefully thought out. In contrast to these 2 new, commercially available outpatient treatments, ACT is a personally-specified product and labor-intensive therapy that demands both acquisition of high standard laboratory procedures and close clinical inpatient monitoring during treatment. It is unique among other anti-melanoma treatments, providing the potential for a durable response following a single, self-limited treatment. This perspective drives the efforts to make this protocol accessible for more patients and to explore modifications that may optimize treatment results.