Autologous designer antigen-presenting cells by gene modification of T lymphocyte blasts with IL-7 and IL-12

Human γδ T cells induce CD8+ T cell antitumor responses via antigen-presenting effect through HSP90-MyD88-mediated activation of JNK

Human Vγ9Vδ2 T cells have attracted considerable attention as novel alternative antigen-presenting cells (APCs) with the potential to replace dendritic cells in antitumor immunotherapy owing to their high proliferative capacity and low cost. However, the utility of γδ T cells as APCs to induce CD8⁺ T cell-mediated antitumor immune response, as well as the mechanism by which they perform APC functions, remains unexplored. In this study, we found that activated Vγ9Vδ2 T cells were capable of inducing robust CD8⁺ T cell responses in osteosarcoma cells. Activated γδ T cells also effectively suppressed osteosarcoma growth by priming CD8⁺ T cells in xenograft animal models. Mechanistically, we further revealed that activated γδ T cells exhibited increased HSP90 production, which fed back to upregulate MyD88, followed by JNK activation and a subsequent improvement in CCL5 secretion, leading to enhanced CD8⁺ T cell cross-priming. Thus, our study suggests that Vγ9Vδ2 T cells represent a promising alternative APC for the development of γδ T cell-based tumor immunotherapy.

Safety and Efficacy of Intratumoral Injections of Chimeric Antigen Receptor (CAR) T Cells in Metastatic Breast Cancer

Chimeric antigen receptors (CAR) are synthetic molecules that provide new specificities to T cells. Although successful in treatment of hematologic malignancies, CAR T cells are ineffective for solid tumors to date. We found that the cell-surface molecule c-Met was expressed in ∼50% of breast tumors, prompting the construction of a CAR T cell specific for c-Met, which halted tumor growth in immune-incompetent mice with tumor xenografts. We then evaluated the safety and feasibility of treating metastatic breast cancer with intratumoral administration of mRNA-transfected c-Met-CAR T cells in a phase 0 clinical trial (NCT01837602). Introducing the CAR construct via mRNA ensured safety by limiting the nontumor cell effects (on-target/off-tumor) of targeting c-Met. Patients with metastatic breast cancer with accessible cutaneous or lymph node metastases received a single intratumoral injection of 3 × 107 or 3 × 108 cells. CAR T mRNA was detectable in peripheral blood and in the injected tumor tissues after intratumoral injection in 2 and 4 patients, respectively. mRNA c-Met-CAR T cell injections were well tolerated, as none of the patients had study drug-related adverse effects greater than grade 1. Tumors treated with intratumoral injected mRNA c-Met-CAR T cells were excised and analyzed by immunohistochemistry, revealing extensive tumor necrosis at the injection site, cellular debris, loss of c-Met immunoreactivity, all surrounded by macrophages at the leading edges and within necrotic zones. We conclude that intratumoral injections of mRNA c-Met-CAR T cells are well tolerated and evoke an inflammatory response within tumors. Cancer Immunol Res; 5(12); 1152-61. ©2017 AACR.

Complementation of antigen-presenting cells to generate T lymphocytes with broad target specificity

Antigen-specific T cells provide a therapy for cancer that is highly specific, self-replicating, and potentially devoid of toxicity. Ideally, tumor-specific T cells should recognize multiple epitopes on multiple antigens to prevent tumor immune escape. However the large-scale expansion of such broad-spectrum T cells has been limited by the availability of potent autologous antigen-presenting cells that can present antigens on the polymorphic array of each patient's HLA allotype. We evaluated a novel antigen-presenting complex (KATpx) in which antigens in the form of peptide libraries can be presented by autologous activated T cells, whereas costimulation is complemented in trans by an HLA-negative K562 cell line genetically modified to express CD80, CD83, CD86, and 4-1BBL (K562cs). The additional costimulation provided by K562cs significantly enhanced T-cell expansion in culture over autologous activated T cells alone while maintaining antigen specificity. We validated this antigen-presenting system by generating Epstein-Barr virus (EBV) antigen-specific T cells from healthy donors and from patients with EBV-positive malignancies including nasopharyngeal carcinoma and multiply relapsed EBV-positive lymphoma. These T cells were specific for EBNA1, LMP1, and LMP2, the viral antigens expressed in these type 2 latency EBV-associated malignancies. The KATpx system consistently activated and expanded antigen-specific T cells both from healthy donors and from 5 of 6 patients with lymphoma and 6 of 6 with nasopharyngeal carcinoma, while simplifying the process for generating APCs by eliminating the need for live virus (EBV) or viral vectors to force expression of transgenic EBV antigens. Hence, KATpx provides a robust, reliable, and scalable process to expand tumor-directed T cells for the treatment of virus-associated cancers.

Modification of T lymphocytes to express tumor antigens

Human T cells can be genetically modified to express tumor-associated antigens (TAA) for the induction of tumor-specific immunity, suggesting that T cells may be alternative candidates of effective antigen-presenting cells (TAPC) and may be useful in vivo as cellular cancer vaccines. The effective induction of TAA-specific T cell immune responses requires activation of T cells by CD3/CD28 antibodies and the presence of proinflammatory cytokines such as interleukin-7 (IL-7) and interleukin-12 (IL-12). Here, we describe the technique of preparing activated human TAPC pulsed with TAA peptides for the induction of tumor antigen-specific T cell immunity in vitro.

Characteristics of new monomolecular chimeric T-cell receptors to carcinoembryonic antigen

We described two original genetic constructs encoding chimeric monomolecular T-cell receptors, where the effector T-cell receptor fragment was linked with the antigen-recognizing part consisting of two variable fragments of two different antibodies to carcinoembryonic antigen. Following transfection, these receptors were expressed on the cell surface and bound carcinoembryonic antigen. Human peripheral blood lymphocytes transfected with the above constructs demonstrated high cytotoxic activity against HCT116 cells expressing carcinoembryonic antigen.

The basic principles of chimeric antigen receptor design

Chimeric antigen receptors (CAR) are recombinant receptors that provide both antigen-binding and T-cell-activating functions. A multitude of CARs has been reported over the past decade, targeting an array of cell surface tumor antigens. Their biologic functions have dramatically changed following the introduction of tripartite receptors comprising a costimulatory domain, termed second-generation CARs. These have recently shown clinical benefit in patients treated with CD19-targeted autologous T cells. CARs may be combined with costimulatory ligands, chimeric costimulatory receptors, or cytokines to further enhance T-cell potency, specificity, and safety. CARs represent a new class of drugs with exciting potential for cancer immunotherapy.

SIGNIFICANCE

CARs are a new class of drugs with great potential for cancer immunotherapy. Upon their expression in T lymphocytes, CARs direct potent, targeted immune responses that have recently shown encouraging clinical outcomes in a subset of patients with B-cell malignancies. This review focuses on the design of CARs, including the requirements for optimal antigen recognition and different modalities to provide costimulatory support to targeted T cells, which include the use of second- and third generation CARs, costimulatory ligands, chimeric costimulatory receptors, and cytokines.

Activated human γδ T cells induce peptide-specific CD8+ T-cell responses to tumor-associated self-antigens

Specific cellular immunotherapy of cancer requires efficient generation and expansion of cytotoxic T lymphocytes (CTLs) that recognize tumor-associated self-antigens. Here, we investigated the capacity of human γδ T cells to induce expansion of CD8+ T cells specific for peptides derived from the weakly immunogenic tumor-associated self-antigens PRAME and STEAP1. Coincubation of aminobisphosphonate-stimulated human peripheral blood-derived γδ T cells (Vγ9+Vδ2+), loaded with HLA-A*02-restricted epitopes of PRAME, with autologous peripheral blood CD8+ T cells stimulated the expansion of peptide-specific cytolytic effector memory T cells. Moreover, peptide-loaded γδ T cells efficiently primed antigen-naive CD45RA+ CD8+ T cells against PRAME peptides. Direct comparisons with mature DCs revealed equal potency of γδ T cells and DCs in inducing primary T-cell responses and peptide-specific T-cell activation and expansion. Antigen presentation by γδ T-APCs was not able to overcome the limited capacity of peptide-specific T cells to interact with targets expressing full-length antigen. Importantly, T cells with regulatory phenotype (CD4+ CD25hiFoxP3+) were lower in cocultures with γδ T cells compared to DCs. In summary, bisphosphonate-activated γδ T cells permit generation of CTLs specific for weakly immunogenic tumor-associated epitopes. Exploiting this strategy for effective immunotherapy of cancer requires strategies that enhance the avidity of CTL responses to allow for efficient targeting of cancer.

T cells as vehicles for cancer vaccination

The success of cancer vaccines is dependent on the delivery of tumor-associated antigens (TAAs) within lymphoid tissue in the context of costimulatory molecules and immune stimulatory cytokines. Dendritic cells (DCs) are commonly utilized to elicit antitumor immune responses due to their attractive costimulatory molecule and cytokine expression profile. However, the efficacy of DC-based vaccines is limited by the poor viability and lymph-node migration of exogenously generated DCs in vivo. Alternatively, adoptively transferred T cells persist for long periods of time in vivo and readily migrate between the lymphoid and vascular compartments. In addition, T cells may be genetically modified to express both TAA and DC-activating molecules, suggesting that T cells may be ideal candidates to serve as cellular vehicles for antigen delivery to lymph node-resident DCs in vivo. This paper discusses the concept of using T cells to induce tumor-specific immunity for vaccination against cancer.

Cytotoxic T lymphocytes simultaneously targeting multiple tumor-associated antigens to treat EBV negative lymphoma

Although immunotherapy with Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) can treat EBV-associated Hodgkin and non-Hodgkin lymphoma (HL/NHL), more than 50% of such tumors are EBV negative. We now describe an approach that allows us to consistently generate, in a single line, CTLs that recognize a wide spectrum of nonviral tumor-associated antigens (TAAs) expressed by human HL/NHL, including Survivin, MAGE-A4, Synovial sarcoma X (SSX2), preferentially expressed antigen in melanoma (PRAME) and NY-ESO-1. We could generate these CTLs from nine of nine healthy donors and five of eight lymphoma patients, irrespective of human leukocyte antigen (HLA) type. We reactivated TAA-directed T cells ex vivo, by stimulation with dendritic cells (DCs) pulsed with overlapping peptide libraries spanning the chosen antigens in the presence of an optimized Th1-polarizing, prosurvival/proliferative and Treg inhibitory cytokine combination. The resultant lines of CD4(+) and CD8(+), polycytokine-producing T cells are directed against a multiplicity of epitopes expressed on the selected TAAs, with cytolytic activity against autologous tumor cells. Infusion of such multispecific monocultures may extend the benefits of CTL therapy to treatment even of EBV negative HL and NHL.

Enhanced tumor trafficking of GD2 chimeric antigen receptor T cells by expression of the chemokine receptor CCR2b

For adoptive T-cell therapy to be effective against solid tumors, tumor-specific T cells must be able to migrate to the tumor site. One requirement for efficient migration is that the effector cells express chemokine receptors that match the chemokines produced either by tumor or tumor-associated cells. In this study, we investigated whether the tumor trafficking of activated T cells (ATCs) bearing a chimeric antigen receptor specific for the tumor antigen GD2 (GD2-CAR) could be enhanced by forced coexpression of the chemokine receptor CCR2b, as this receptor directs migration toward CCL2, a chemokine produced by many tumors, including neuroblastoma. Neuroblastoma cell lines (SK-N-SH and SK-N-AS) and primary tumor cells isolated from 6 patients all secreted high levels of CCL2, but GD2-CAR transduced ATCs lacked expression of CCR2 (<5%) and migrated poorly to recombinant CCL2 or tumor supernatants. After retroviral transduction, however, ATCs expressed high levels of CCR2b (>60%) and migrated well in vitro. We expressed firefly luciferase in CCR2b-expressing ATCs and observed improved homing (>10-fold) to CCL2-secreting neuroblastoma compared with CCR2-negative ATCs. As a result, ATCs co-modified with both CCR2b and GD2-CAR had greater antitumor activity in vivo.

T cells expressing constitutively active Akt resist multiple tumor-associated inhibitory mechanisms

Adoptive transfer of antigen-specific cytotoxic T lymphocytes has shown promise for the therapy of cancer. However, tumor-specific T cells are susceptible to diverse inhibitory signals from the tumor microenvironment. The Akt/protein kinase B plays a central role in T-cell proliferation, function, and survival and we hypothesized that expression of constitutively active Akt (caAkt) in T cells could provide resistance to many of these tumor-associated inhibitory mechanisms. caAkt expression in activated human T cells increased proliferation and cytokine production, a likely result of their sustained expression of nuclear factor-κB (NF-κB) and provided resistance to apoptosis by upregulating antiapoptotic molecules. caAkt expressing T cells (caAkt-T-cells) were also relatively resistant to suppression by and conversion into regulatory T cells (Tregs). These characteristics provided a survival advantage to T cells cocultured with tumor cells in vitro; CD3/28-stimulated T cells expressing a chimeric antigen receptor (CAR) specific for disialoganglioside (GD2) that redirected their activity to the immunosuppressive, GD2-expressing neuroblastoma cell line, LAN-1, resisted tumor-induced apoptosis when co-expressing transgenic caAkt. In conclusion, caAkt-transduced T cells showed resistance to several evasion strategies employed by tumors and may therefore enhance the antitumor activity of adoptively transferred T lymphocytes.

Optimization and validation of a robust human T-cell culture method for monitoring phenotypic and polyfunctional antigen-specific CD4 and CD8 T-cell responses

BACKGROUND AIMS

Monitoring cellular immune responses is one prerequisite for the rational development of cancer vaccines.

METHODS

We describe an extensive effort to optimize and validate quantitatively an in vitro T-cell culture method by determining the phenotype and function of both CD4(+) and CD8(+) T cells, including measurement of the phenotype markers CCR7, CD45RA, CD28 and CD27 and the functional markers interferon (IFN)-gamma, interleukin (IL)-2, macrophage inflammatory protein (MIP)-1beta, tumor necrosis factor (TNF)-alpha and CD107a.

RESULTS

Autologous peripheral blood mononuclear cells (PBMC) were potent stimulators that expanded antigen (Ag)-specific CD8(+) T cells during short-term culture with the addition of IL-2 and IL-15 cytokines. Polyfunctional Ag-specific CD4(+) and CD8(+) T cells were detectable using this method.

CONCLUSIONS

Our culture system represents a robust human T-cell culture protocol that permits phenotypic, quantitative and qualitative evaluation of vaccine-induced CD4(+) and CD8(+) T-cell responses.

Selective elimination of a chemoresistant side population of B-CLL cells by cytotoxic T lymphocytes in subjects receiving an autologous hCD40L/IL-2 tumor vaccine

Side-population (SP) analysis identifies precursor cells in normal and malignant tissues. Cells with this phenotype have increased resistance to many cytotoxic agents, and in malignant disease may represent a primary drug resistant population. To discover whether drug resistant malignant SP cells are nonetheless sensitive to immune-mediated killing, we first established the presence of a malignant CD5⁺CD19⁺ SP subset in the blood of 18/21 subjects with B-CLL. We examined the fate of these cells in 6 of these individuals who received autologous hCD40L/IL-2 gene-modified tumor cells as part of a tumor vaccine study. Vaccinated patients showed an increase in B-CLL-reactive T cells followed by a corresponding decline in circulating CD5⁺CD19⁺ SP cells. T cell lines and clones generated from vaccinated patients specifically recognized B-CLL SP tumor cells. Elimination of SP cells is likely triggered by their increased expression of target antigens such as RHAMM following stimulation of the malignant cells by hCD40L, since CD8⁺ RHAMM-specific T cells could be detected in the peripheral blood of immunized patients and were associated with the decline in B-CLL SP cells. Hence malignant B cells with a primary drug resistant phenotype can be targeted by T cell mediated effector activity following immunization of human subjects.

Treatment of lymphoma with adoptively transferred T cells

BACKGROUND

Chemotherapy-resistant lymphomas can be cured with allogeneic hematopoietic cell transplantation, demonstrating the susceptibility of these tumors to T cell mediated immune responses. However, high rates of transplant-related morbidity and mortality limit this approach. Efforts have, therefore, been made to develop alternative T cell based therapies, and there is growing evidence that adoptive therapy with T cells targeted to lymphoma-associated antigens may be a safe and effective new method for treating this group of diseases.

OBJECTIVE/METHODS

We review publications on adoptive therapy with ex vivo expanded T cells targeting viral antigens, as well as genetically modified autologous T cells, as strategies for the treatment of lymphoma, with the goal of providing an overview of these approaches.

RESULTS/CONCLUSIONS

Epstein-Barr virus specific T cell therapy is an effective and safe method of treating Epstein-Barr virus associated lymphomas; however, most lymphoma subtypes do not express EBV antigens. For these diseases, adoptive immunotherapy with genetically modified T cells expressing chimeric T cell receptors targeting lymphoma-associated antigens such as CD19 and CD20 appears to be a promising alternative. Recent innovations including enhanced co-stimulation, exogenous cytokine administration and use of memory T cells promise to overcome many of the limitations and pitfalls initially encountered with this approach.

Genetic modification of T cells with IL-21 enhances antigen presentation and generation of central memory tumor-specific cytotoxic T-lymphocytes

An optimized antigen-presenting cell for tumor immunotherapy should produce a robust antigen specific cytotoxic T lymphocytes (CTL) response to tumor-associated antigens, which can persist in vivo and expand on antigen reencounter. Interleukin (IL)-21 synergizes with other gamma-chain cytokines to enhance the frequency and cytotoxicity of antigen-specific CTL. As T cells themselves may serve as effective antigen-presenting cells (T antigen-presenting cells; TAPC) and may be useful in vivo as cellular vaccines, we examined whether CD8(+) T cells genetically modified to produce IL-21 could induce immune responses to tumor associated antigen peptides in healthy human leukocyte antigen-A2(+) donors. We found that IL-21 modified TAPC enhanced both the proliferation and survival of MART-1 specific CD8(+) T cells, which were enriched by >8-fold over cultures with control nontransgenic TAPC. MART-1-specific CTL produced interferon-gamma in response to cognate peptide antigen and killed primary tumor cells expressing MART-1 in a major histocompatibility complex restricted manner. IL-21 modified TAPC similarly enhanced generation of functional CTL against melanoma antigen gp100 and the B-cell chronic lymphocytic leukemia associated RHAMM antigen. Antigen-specific CTL generated using IL-21 gene-modified TAPC had a central memory phenotype characterized by CD45RA(-), CD44(high), CD27(high), CD28(high), CD62L(high), and IL-7 receptor-alpha(high), contrasting with the terminal effector phenotype of CTL generated in the absence of IL-21. Thus, TAPC stimulation in the presences of IL-21 enhances proliferation of tumor antigen-specific T cells and favors induction of a central memory phenotype, which may improve proliferation, survival, and efficacy of T-cell based therapies for the treatment of cancer.

Activated human gammadelta T cells as stimulators of specific CD8+ T-cell responses to subdominant Epstein Barr virus epitopes: potential for immunotherapy of cancer

The efficacy of current cancer vaccines is limited by the functional heterogeneity and poor availability and expansion of professional antigen-presenting cells (APCs). Besides their potent innate effector properties, gammadelta T cells have been suggested to be involved in the initiation and maintenance of adaptive immune responses. Here, we investigated the capacity of human gammadelta T cells to induce expansion of virus-specific T cells to Epstein Barr virus (EBV) antigens. Aminobisphosphonate-stimulated human peripheral blood-derived gammadelta T cells (Vgamma2+Vdelta2+) acquired a dual phenotype characteristic for both APCs and effector memory T cells. Coincubation of activated gammadelta T cells pulsed with human leukocyte antigen-restricted epitopes of either the highly stimulatory EBV lytic cycle antigen Bam H1 Z fragment leftward open reading frame or the tumor-associated latent EBV antigen latent membrane protein 2a (LMP2a) with autologous peripheral blood lymphocytes induced selective expansion of peptide-specific, fully functional CD3CD8 cytolytic effector memory T cells. Furthermore, gammadelta T APCs efficiently processed and presented endogenous antigen, as demonstrated by the capacity of LMP2a gene-transduced gammadelta T cells to induce expansion of T cells with broad specificity for various LMP2a peptides. The capacity of autologous gammadelta T cells to induce LMP2a-specific autologous cytotoxic T lymphocytes was confirmed in 2 patients with Hodgkin lymphoma. In summary, bisphosphonate-activated human gammadelta T cells stimulate expansion of cytotoxic effector T cells specific for both subdominant and dominant viral epitopes and thus show promise as a novel source of efficient APCs for immunotherapy of viral and malignant disease.

Permanent silencing of NKG2A expression for cell-based therapeutics

Natural killer (NK) and T-cell cytotoxicity is significantly reduced by signaling via CD94/NKG2A receptors. High levels of NKG2A on NK cells have been shown to compromise the graft-versus-leukemia effect in hematopoietic stem cell transplantation. We therefore evaluated the functional relevance of NKG2A silencing for the cytotoxic potential of genetically engineered NK and T cells. Lentiviral vectors containing short hairpin RNA (shRNA) sequences targeting NKG2A transcripts were used to transduce NKG2A(+) primary NK and T cells. NKG2A expression levels were measured by flow cytometry and real-time PCR. The effect of NKG2A silencing on the cytolytic potential of NK and T cells was evaluated in cytotoxicity assays using K562 and B lymphoblastoid cells as targets. Granzyme B mRNA transcript levels were detected by real-time PCR. The transduction of inducible RNAi cassettes containing the sequences for shRNAs targeting NKG2A reduced protein expression in NK and T cells by up to 95%. The cytotoxicity assays demonstrated that NKG2A silencing effectively enhanced NK and CD8+ T-cell lysis by up to 40% and 15%, respectively. However, lysis of K562 cells which lack human leukocyte antigen-E, the ligand of NKG2A, was associated with an upregulation of the natural cytotoxicity receptor NKp30 in NKG2A-silenced NK cells. Our data suggest that RNAi-mediated silencing of NKG2A in effector cells could improve the efficacy of cell-based immunotherapies but also show that indirect effects of NKG2A knockdown exist that have to be considered when designing therapeutic protocols with genetically engineered NK or T cells.

Identification of hexon-specific CD4 and CD8 T-cell epitopes for vaccine and immunotherapy

Adenoviral infections in the immunocompromised host are associated with significant morbidity and mortality. Although the adoptive transfer of adenovirus-specific T cells may prevent and treat such infections, the T-cell immune response to the multiplicity of adenovirus serotypes and subspecies that infect humans has not been well characterized, impeding the development of such approaches. We have, therefore, analyzed the specificities of T-cell responses to the viral capsid hexon antigen, since this structure is highly conserved in human pathogens. We screened 25 human cytotoxic T-cell lines with adenovirus specificity to extensively characterize their responses to adenoviral hexon and to identify a panel of novel CD4(+) and CD8(+) T-cell epitopes. Using a peptide library spanning the entire sequence of the hexon protein, we confirmed the responsiveness of these cytotoxic T-cell lines to seven peptides described previously and also identified 33 new CD4- or CD8-restricted hexon epitopes. Importantly, the majority of these epitopes were shared among different adenovirus subspecies, suggesting that T cells with such specificities could recognize and be protective against multiple serotypes, simplifying the task of effective adoptive transfer or vaccine-based immunotherapy for treating infection by this virus.

Adoptive cellular immunotherapy for childhood malignancies

Clinical trials have established that T cells have the ability to prevent and treat pathogens and tumors. This is perhaps best exemplified by engraftment of allogeneic T cells in the context of hematopoietic stem-cell transplantation (HSCT), which for over the last 50 years remains one of the best and most robust examples of cell-based therapies for the treatment of hematologic malignancies. Yet, the approach to infuse T cells for treatment of cancer, in general, and pediatric tumors, in particular, generally remains on the sidelines of cancer therapy. This review outlines the current state-of-the-art and provides a rationale for undertaking adoptive immunotherapy trials with emphasis on childhood malignancies.