Generation of peptide-specific CD8+ T cells by phytohemagglutinin-stimulated antigen-mRNA-transduced CD4+ T cells

Cancer/Testis Antigens as Targets for RNA-Based Anticancer Therapy

In the last few decades, RNA-based drugs have emerged as a promising candidate in the treatment of various diseases. The introduction of messenger RNA (mRNA) as a vaccine or therapeutic agent enables the production of almost any functional protein/peptide. The key to applying RNA therapy in clinical trials is developing safe and effective delivery systems. Exosomes and lipid nanoparticles (LNPs) have been exploited as promising vehicles for drug delivery. This review discusses the feasibility of exosomes and LNPs as vehicles for mRNA delivery. Cancer/testis antigens (CTAs) show restricted expression in normal tissues and widespread expression in cancer tissues. Many of these CTAs show expression in the sera of patients with cancers. These characteristics of CTAs make them excellent targets for cancer immunotherapy. This review summarizes the roles of CTAs in various life processes and current studies on mRNAs encoding CTAs. Clinical studies present the beneficial effects of mRNAs encoding CTAs in patients with cancers. This review highlight clinical studies employing mRNA-LNPs encoding CTAs.

Optimization of Culture Media for Ex vivo T-Cell Expansion for Adoptive T-Cell Therapy

BACKGROUND

Adoptive T-cell therapy is a promising treatment strategy for cancer immunotherapy. The ability of immunotherapy based on the adoptive cell transfer of genetically modified T cells to generate powerful clinical responses has been highlighted by recent clinical success. Techniques which are used to expand large numbers of T cells from different sources are critical in adoptive cell therapy. In this study, we evaluated the expansion, proliferation, activation of T lymphocytes, in the presence of various concentrations of interleukin-2, phytohemagglutinin (PHA), and insulin.

MATERIALS AND METHODS

The effect of different supplemented culture media on T cell expansion was evaluated using MTT assay. The expression level of the Ki-67 proliferation marker was evaluated by real-time polymerase chain reaction. In addition, flow cytometry analysis was performed to access T cell subpopulations.

RESULTS

Our results showed that supplemented culture media with an optimized concentration of PHA and interleukin-2 increased total fold expansion of T cells up to 500-fold with approximately 90% cell viability over 7 days. The quantitative assessment of Ki-67 in expanded T cells showed a significant elevation of this proliferation marker. Flow cytometry was also used to assess the proportion of CD4+ and CD8+ cells, and the main expanded population was CD3+ CD8+ cells.

CONCLUSIONS

Based on these findings, we introduced a low-cost and rapid method to support the efficient expansion of T cells for adoptive cell therapy and other in vivo experiments.

Adoptive cancer immunotherapy using DNA-demethylated T helper cells as antigen-presenting cells

In cancer cells, cancer/testis (CT) antigens become epigenetically derepressed through DNA demethylation and constitute attractive targets for cancer immunotherapy. Here we report that activated CD4⁺ T helper cells treated with a DNA-demethylating agent express a broad repertoire of endogenous CT antigens and can be used as antigen-presenting cells to generate autologous cytotoxic T lymphocytes (CTLs) and natural killer cells. In vitro, activated CTLs induce HLA-restricted lysis of tumor cells of different histological types, as well as cells expressing single CT antigens. In a phase 1 trial of 25 patients with recurrent glioblastoma multiforme, cytotoxic lymphocytes homed to the tumor, with tumor regression ongoing in three patients for 14, 22, and 27 months, respectively. No treatment-related adverse effects were observed. This proof-of-principle study shows that tumor-reactive effector cells can be generated ex vivo by exposure to antigens induced by DNA demethylation, providing a novel, minimally invasive therapeutic strategy for treating cancer.

Hypoxia-inducing factor (HIF)-1α-derived peptide capable of inducing cancer-reactive cytotoxic T lymphocytes from HLA-A24+ patients with renal cell carcinoma

Hypoxic tumor microenvironment makes cancer cells to be therapy-resistant and hypoxia-inducing factors (HIFs) play a central role in hypoxic adaptation. Especially, renal cell carcinoma (RCC) is often associated with von Hippel-Lindau (VHL) gene mutations, leading to up-regulation of HIFs. However, from a different point of view, this suggests the possibility that HIFs could be promising targets in anti-cancer therapy. In this study, we searched for HIF-1α-derived peptides that are able to induce RCC-reactive cytotoxic T lymphocytes (CTLs) from HLA-A24⁺ RCC patients. Among five peptides derived from HIF-1α, which were prepared based on the binding motif to the HLA-A24 allele, a HIF-1α_278-287 peptide induced peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A24⁺ RCC patients most effectively. In immunoblot assays, the expression of HIF-1α was lowly detected in whole and nuclear lysates of RCC cell lines even under normoxia (20% O₂), and their expression in whole lysates was increased under hypoxia (1% O₂). Additionally, HIF-1α_278-287 peptide-stimulated T cells showed a higher cytotoxicity against HLA-A24⁺ HIF-1α-expressing RCC cells than against HLA-A24^- HIF-1α-expressing RCC cells. The cytotoxicity was inhibited by the addition of HIF-1α_278-287 peptide-pulsed cold target cells. Altogether, these results indicate that the HIF-1α_278-287 peptide could be a candidate for peptide-based anti-cancer vaccines for HLA-A24⁺ RCC patients.

Enhancement of tumor-reactive cytotoxic CD4+ T cell responses after ipilimumab treatment in four advanced melanoma patients

CD4(+) T cells provide help to enhance and sustain cytotoxic CD8(+) T cell responses. A direct lytic role for this cell population in mouse models further supports the use of tumor-reactive CD4(+) T cells for cancer immunotherapy. CTLA-4 blockade has been shown to expand antigen-specific cytotoxic CD4(+) T cells in mouse models. We took advantage of spontaneous immunity to the NY-ESO-1 cancer-testis antigen to investigate quantitative and qualitative changes in antigen-specific CD4(+) T cell responses after ipilimumab (anti-CTLA-4 monoclonal antibody) treatment in advanced melanoma patients. Four NY-ESO-1 seropositive melanoma patients were chosen upon the availability of suitable blood specimens for characterizing the functions of NY-ESO-1 antigen-specific CD4(+) T cell response by enzyme-linked immunospot (ELISPOT), intracellular cytokine staining (ICS) and cytotoxicity assays. Multiple NY-ESO-1 antigen-specific CD4(+) T cell responses with Th1 dominance were induced or enhanced after ipilimumab treatment in peripheral blood in all four patients. NY-ESO-1 antigen-specific CD4(+) T cell lines established from all 4 patients after ipilimumab treatment recognized naturally processed NY-ESO-1 protein in antigen-presenting cells, expressed master transcription factor Eomesodermin (Eomes) and secreted perforin and Granzyme B. Finally, we demonstrated that these NY-ESO-1 antigen-specific CD4(+) T cell lines directly lysed autologous melanoma cell lines expressing NY-ESO-1 in an MHC class II restricted manner. Our results show that antigen specific cytotoxic CD4(+) T cell responses are induced after ipilimumab therapy in human cancer patients. Ipilimumab may induce the expression of lytic granules on antigen specific cytotoxic CD4(+) T cells via Eomes, revealing a novel consequence of immunologic checkpoint blockade.

Identification of erythropoietin receptor-derived peptides having the potential to induce cancer-reactive cytotoxic T lymphocytes from HLA-A24(+) patients with renal cell carcinoma

Molecular targeting therapy with anti-angiogenic agents, including sunitinib and sorafenib, has been proven to be the first- and second-line standard treatments for metastatic renal cell carcinoma (mRCC) worldwide. Despite their significant antitumor effects, most of the patients with mRCC have not been cured. Under such circumstances, anti-cancer immunotherapy has been considered as a promising treatment modality for mRCC, and cytotoxic T lymphocytes (CTLs) are the most powerful effectors among several immune cells and molecules. Therefore, we previously conducted anti-cancer vaccine therapy with peptides derived from carbonic anhydrase-9 and vascular endothelial growth factor receptor-1 as phase-I/II trials for mRCC patients and reported their clinical benefits. Alternatively, up-regulated expression of erythropoietin (Epo) and its receptor (EpoR) in RCC has been reported, and their co-expression is involved in tumorigenesis. In order to increase options for peptide-based vaccination therapy, we searched for novel EpoR-peptides for HLA-A24(+) RCC patients. Among 5 peptides derived from EpoR, which were prepared based on the binding motif to the HLA-A24 allele, EpoR52-60 peptide had the potential to induce peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A24(+) RCC patients. Cytotoxicity toward HLA-A24(+) and EpoR-expressing RCC cells was ascribed to peptide-specific CD8(+) T cells. These results indicate that the EpoR52-60 peptide could be a promising candidate for a peptide-based anti-cancer vaccine for HLA-A24(+) mRCC patients.

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.

Evaluation of cellular immune responses in cancer vaccine recipients: lessons from NY-ESO-1

The rigorous evaluation of cancer vaccination requires evidence of benefit to patients with cancer or those at risk of relapse from the disease. Clinical trials are expensive and require considerable human and clinical resources in order to demonstrate this benefit. In the era of defined cancer antigens, it is possible to evaluate immunogenic targets, and assess the quality and magnitude of immune responses against these antigens following vaccination. Analyzing these surrogate end points complements clinical assessment and provides a depth of understanding to better inform trial evaluation and design. We have used the immunogenic cancer testis antigen NY-ESO-1 as a model antigen. This article summarizes our experience in monitoring immunity against NY-ESO-1.

An in vitro-transcribed-mRNA polyepitope construct encoding 32 distinct HLA class I-restricted epitopes from CMV, EBV, and Influenza for use as a functional control in human immune monitoring studies

Interest and activity in the areas of clinical immunotherapy and therapeutic vaccines are growing dramatically, thus there is a pressing need to develop robust tools for assessment of vaccine-induced immunity. CD8+ T cell immunity against specific antigens is normally measured by either flow cytometry using MHC tetramer reagents or via biological assays such as intracellular cytokine staining or ELISPOT after stimulation with specific peptide epitopes. However, these methodologies depend on precise knowledge of HLA-restricted epitopes combined with HLA typing of subjects. As an alternative approach, electroporation of antigen presenting cells (APC) with in vitro-transcribed mRNA (IVT-mRNA) encoding the antigen of interest bypasses the requirements for HLA typing and knowledge of specific epitopes. A current limitation of the IVT-mRNA technique is the lack of robust positive control RNAs to verify the efficacy of electroporation and to ensure that the electroporated APC retain the ability to stimulate T cells. Herein we describe an IVT-mRNA construct wherein all 32 HLA class I-restricted epitopes of the widely used CEF (Cytomegalovirus, Epstein-Barr Virus and Influenza Virus) positive control peptide pool have been genetically spliced together to generate a single polyepitope construct. Each epitope is flanked by three amino- and three carboxy-terminal amino acids from the original parent protein to facilitate proteolytic processing by the proteasome. Using cells obtained from a panel of normal healthy donors and cancer patients we report that dendritic cells, CD40-activated B cells, PHA blasts, and even tumor cells can be transfected with CEF polyepitope IVT-mRNA and can elicit robust CEF-specific responses from autologous T cells, as measured by IFN-gamma ELISPOT. Moreover, the response elicited by CEF IVT-mRNA-transfected APC was similar in magnitude to the response elicited by the complete pool of CEF minimal peptide epitopes, implying that the polyepitope parent protein encoded by the CEF mRNA was efficiently processed into individual epitopes by the proteolytic machinery of the APC. In summary, the CEF polyepitope IVT-mRNA described herein comprises a robust positive control for immunomonitoring studies requiring IVT-mRNA transfection and potentially provides a unique tool for assessing MHC class I processing regardless of HLA haplotype.

Modified tumour antigen-encoding mRNA facilitates the analysis of naturally occurring and vaccine-induced CD4 and CD8 T cells in cancer patients

The development of effective anti-cancer vaccines requires precise assessment of vaccine-induced immunity. This is often hampered by low ex vivo frequencies of antigen-specific T cells and limited defined epitopes. This study investigates the applicability of modified, in vitro-transcribed mRNA encoding a therapeutically relevant tumour antigen to analyse T cell responses in cancer patients. In this study transfection of antigen presenting cells, by mRNA encoding the tumour antigen NY-ESO-1, was optimised and applied to address spontaneous and vaccine-induced T cell responses in cancer patients. Memory CD8+ T cells from lung cancer patients having detectable humoral immune responses directed towards NY-ESO-1 could be efficiently detected in peripheral blood. Specific T cells utilised a range of different T cell receptors, indicating a polyclonal response. Specific killing of a panel of NY-ESO-1 expressing tumour cell lines indicates recognition restricted to several HLA allelic variants, including a novel HLA-B49 epitope. Using a modified mRNA construct targeting the translated antigen to the secretory pathway, detection of NY-ESO-1-specific CD4+ T cells in patients could be enhanced, which allowed the in-depth characterisation of established T cell clones. Moreover, broad CD8+ and CD4+ T cell responses covering multiple epitopes were detected following mRNA stimulation of patients treated with a recombinant vaccinia/fowlpox NY-ESO-1 vaccine. This approach allows for a precise monitoring of responses to tumour antigens in a setting that addresses the breadth and magnitude of antigen-specific T cell responses, and that is not limited to a particular combination of known epitopes and HLA-restrictions.

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

An effective immune response to antigen requires professional antigen-presenting cell (APC), which not only present antigen, but also provide costimulation and cytokines (eg, IL-12) that drive T cell differentiation down the appropriate effector pathway (Tc1/TH1). For T cell-based immunotherapy protocols, the availability of large numbers of autologous professional APC is a major limitation because professional APC do not proliferate in vitro. T cells themselves can proliferate exponentially in vitro and have the ability to present antigen. They can also express costimulatory molecules after activation. Therefore, we hypothesized that if activated T cells were genetically modified to express proinflammatory cytokines required to polarize T cells toward a Tc1 response, they could fulfill the requirements for an abundant, autologous APC. To test this potential, T cells were activated by CD3/CD28 antibodies and pulsed with model HLA-A2+ peptides derived from CMVpp65, MAGE-3, and MART-1. Activated T-APC readily reactivated CD8 pp65 memory T cells from healthy CMV seropositive donors; however, the activation of MAGE-3 and MART-1-specific CD8 T cells required both IL-7 and IL-12, which could be provided either exogenously or by genetic modification of the T-APC. Responder T cells could be expanded to large numbers with subsequent stimulations using activated, peptide-pulsed T-APC and IL-2. Tumor antigen-specific T cell lines killed both peptide-pulsed target cells and tumor cell lines. Thus, T cells provide a platform for the generation of autologous APC that can be customized to express both antigens and therapeutic molecules for the induction of antigen-specific T cell immunity.

HER2-specific T-cell immune responses in patients vaccinated with truncated HER2 protein complexed with nanogels of cholesteryl pullulan

PURPOSE

We developed a complex of tumor antigen protein with a novel nanoparticle antigen delivery system of cholesteryl pullulan (CHP). To target HER2 antigen, we prepared truncated HER2 protein 1-146 (146HER2) complexed with CHP, the CHP-HER2 vaccine. We designed a clinical study to assess the safety of the vaccine and HER2-specific T-cell immune responses measured by the newly developed enzyme-linked immunospot assay with mRNA-transduced phytohemagglutinin-stimulated CD4(+) T cells in HLA-A2402-positive patients with therapy-refractory HER2-expressing cancers.

EXPERIMENTAL DESIGN

Nine patients with various types of solid tumors were enrolled. Each patient was s.c. vaccinated biweekly with 300 microg of CHP-HER2 vaccine for three times followed by booster doses. HER2-specific T-cell responses were evaluated by enzyme-linked immunospot assay by targeting autologous phytohemagglutinin-stimulated CD4(+) T cells transduced with 146HER2-encoding mRNA to cover both identified peptides and unknown epitopes for MHC class I and class II that might exist in the sequence of the vaccine protein.

RESULTS

CHP-HER2 vaccine was well tolerated; the only adverse effect was grade 1 transient skin reaction at the sites of vaccination. HER2-specific CD8(+) and/or CD4(+) T-cell immune responses were detected in five patients who received four to eight vaccinations, among whom both T-cell responses were detected in these patients. In four patients with CD8(+) T-cell responses, two patients reacted to previously identified HER2(63-71) peptide and the other two reacted only to 146HER2 mRNA-transduced cells.

CONCLUSIONS

CHP-HER2 vaccine was safe and induced HER2-specific CD8(+) and/or CD4(+) T-cell immune responses.