An HLA-A3-binding prostate acid phosphatase-derived peptide can induce CTLs restricted to HLA-A2 and -A24 alleles

Promiscuous Recognition of a Trypanosoma cruzi CD8+ T Cell Epitope among HLA-A2, HLA-A24 and HLA-A1 Supertypes in Chagasic Patients

Background

TcTLE is a nonamer peptide from Trypanosoma cruzi KMP-11 protein that is conserved among different parasite strains and that is presented by different HLA-A molecules from the A2 supertype. Because peptides presented by several major histocompatibility complex (MHC) supertypes are potential targets for immunotherapy, the aim of this study was to determine whether MHC molecules other than the A2 supertype present the TcTLE peptide.

Methodology/Principal Findings

From 36 HLA-A2-negative chagasic patients, the HLA-A genotypes of twenty-eight patients with CD8⁺ T cells that recognized the TcTLE peptide using tetramer (twenty) or functional (eight) assays, were determined. SSP-PCR was used to identify the A locus and the allelic variants. Flow cytometry was used to analyze the frequency of TcTLE-specific CD8⁺ T cells, and their functional activity (IFN-γ, TNFα, IL-2, perforin, granzyme and CD107a/b production) was induced by exposure to the TcTLE peptide. All patients tested had TcTLE-specific CD8⁺ T cells with frequencies ranging from 0.07–0.37%. Interestingly, seven of the twenty-eight patients had HLA-A homozygous alleles: A*24 (5 patients), A*23 (1 patient) and A*01 (1 patient), which belong to the A24 and A1 supertypes. In the remaining 21 patients with HLA-A heterozygous alleles, the most prominent alleles were A24 and A68. The most common allele sub-type was A*2402 (sixteen patients), which belongs to the A24 supertype, followed by A*6802 (six patients) from the A2 supertype. Additionally, the A*3002/A*3201 alleles from the A1 supertype were detected in one patient. All patients presented CD8⁺ T cells producing at least one cytokine after TcTLE peptide stimulation.

Conclusion/Significance

These results show that TcTLE is a promiscuous peptide that is presented by the A24 and A1 supertypes, in addition to the A2 supertype, suggesting its potential as a target for immunotherapy.

Immunotherapy for prostate cancer: lessons from responses to tumor-associated antigens

Prostate cancer (PCa) is the most common cancer in men and the second most common cause of cancer-related death in men. In recent years, novel therapeutic options for PCa have been developed and studied extensively in clinical trials. Sipuleucel-T is the first cell-based immunotherapeutic vaccine for treatment of cancer. This vaccine consists of autologous mononuclear cells stimulated and loaded with an immunostimulatory fusion protein containing the prostate tumor antigen prostate acid posphatase. The choice of antigen might be key for the efficiency of cell-based immunotherapy. Depending on the treatment strategy, target antigens should be immunogenic, abundantly expressed by tumor cells, and preferably functionally important for the tumor to prevent loss of antigen expression. Autoimmune responses have been reported against several antigens expressed in the prostate, indicating that PCa is a suitable target for immunotherapy. In this review, we will discuss PCa antigens that exhibit immunogenic features and/or have been targeted in immunotherapeutic settings with promising results, and we highlight the hurdles and opportunities for cancer immunotherapy.

Cross-allele cytotoxic T lymphocyte responses against 2009 pandemic H1N1 influenza A virus among HLA-A24 and HLA-A3 supertype-positive individuals

Lack of a universal vaccine against all serotypes of influenza A viruses and recent progress on T cell-related vaccines against influenza A virus illuminate the important role of human leukocyte antigen (HLA)-restricted cytotoxic T lymphocytes (CTLs) in anti-influenza virus immunity. However, the diverse HLA alleles among humans complicate virus-specific cellular immunity research, and elucidation of cross-HLA allele T cell responses to influenza virus specificity requires further detailed work. An ideal CTL epitope-based vaccine would cover a broad spectrum of epitope antigens presented by most, if not all, of the HLAs. Here, we evaluated the 2009 pandemic influenza A (H1N1) virus-specific T cell responses among the HLA-A24(+) population using a rationally designed peptide pool during the 2009 pandemic. Unexpectedly, cross-HLA allele T cell responses against the influenza A virus peptides were detected among both HLA-A11(+) and HLA-A24(+) donors. Furthermore, we found cross-responses in the entire HLA-A3 supertype population (including HLA-A11, -A31, -A33, and -A30). The cross-allele antigenic peptides within the peptide pool were identified and characterized, and the crystal structures of the major histocompatibility complex (MHC)-peptide complexes were determined. The subsequent HLA-A24-defined cross-allele peptides recognized by the HLA-A11(+) population were shown to mildly bind to the HLA-A*1101 molecule. Together with the structural models, these results partially explain the cross-allele responses. Our findings elucidate the promiscuity of the cross-allele T cell responses against influenza A viruses and are beneficial for the development of a T cell epitope-based vaccine applied in a broader population.

Tumor-associated antigens for specific immunotherapy of prostate cancer

Prostate cancer (PCa) is the most common noncutaneous cancer diagnosis and the second leading cause of cancer-related deaths among men in the United States. Effective treatment modalities for advanced metastatic PCa are limited. Immunotherapeutic strategies based on T cells and antibodies represent interesting approaches to prevent progression from localized to advanced PCa and to improve survival outcomes for patients with advanced disease. CD8⁺ cytotoxic T lymphocytes (CTLs) efficiently recognize and destroy tumor cells. CD4⁺ T cells augment the antigen-presenting capacity of dendritic cells and promote the expansion of tumor-reactive CTLs. Antibodies mediate their antitumor effects via antibody-dependent cellular cytotoxicity, activation of the complement system, improving the uptake of coated tumor cells by phagocytes, and the functional interference of biological pathways essential for tumor growth. Consequently, several tumor-associated antigens (TAAs) have been identified that represent promising targets for T cell- or antibody-based immunotherapy. These TAAs comprise proteins preferentially expressed in normal and malignant prostate tissues and molecules which are not predominantly restricted to the prostate, but are overexpressed in various tumor entities including PCa. Clinical trials provide evidence that specific immunotherapeutic strategies using such TAAs represent safe and feasible concepts for the induction of immunological and clinical responses in PCa patients. However, further improvement of the current approaches is required which may be achieved by combining T cell- and/or antibody-based strategies with radio-, hormone-, chemo- or antiangiogenic therapy.

Phase I clinical study of a personalized peptide vaccination available for six different human leukocyte antigen (HLA-A2, -A3, -A11, -A24, -A31 and -A33)-positive patients with advanced cancer

The majority of peptide-based cancer vaccines under development are for human leukocyte antigen (HLA)-A2- or -A24-positive patients. To overcome this limitation, we conducted a phase I clinical study of peptide vaccines designed for cancer patients with six different HLA-A types. Eligible patients were required to have failed prior standard cancer therapies and to be positive for the HLA-A2, -A24 or -A3 (A3, A11, A31 and A33) supertype. Three sets of 8 candidate peptides (24 peptides in total) were provided for vaccination to HLA-A2(+), HLA-A24(+) and HLA-A3(+) patients, respectively. Personalization of the vaccination peptides from the candidate pool was made by considering the patients' HLA types and pre-existing levels of IgGs to the candidate peptides. Seventeen patients were enrolled in this study. The peptide vaccinations were well tolerated in all patients with no vaccine-related severe adverse events. Augmentation of cytotoxic T lymphocyte (CTL) or IgG responses specific to the vaccinated peptides was observed in 11 or 10 out of 13 cases tested, respectively. This new type of vaccine is recommended for phase II clinical trial because of its tolerability and the immune responses to the vaccinated peptides.

A β-tubulin 5-derived peptide induces cytotoxic T lymphocytes restricted to the HLA-A24 allele in prostate cancer patients

To facilitate the development of a peptide-based cancer vaccine for prostate cancer patients, we examined whether any of the 13 peptides previously reported to induce HLA-class I-restricted cytotoxic T lymphocyte (CTL) activity in HLA-A3 supertype (-A3, -A11, -A31 and -A33)-positive prostate cancer patients are also capable of inducing CTLs restricted to HLA-A2, HLA-A24 or HLA-A26 alleles. Among the 13 peptides tested, a peptide at positions 309 to 318 of β-tubulin 5 exhibited binding activity to the HLA-A(*)2402 molecule and induced HLA-A24-restricted CTL activity against prostate cancer cells derived from peripheral blood mononuclear cells of prostate cancer patients. The CTL activity was determined to be specific to this peptide and was mediated by CD8(+) T cells in an HLA-class I-restricted manner. These results suggest that this peptide could be applicable as a peptide vaccine, not only for HLA-A3 supertype-positive, but also for HLA-A24-positive prostate cancer patients.

Identification of peptides applicable as vaccines for HLA-A26-positive cancer patients

One-fifth of the Japanese population is positive for HLA-A26, but few peptides are available as potential cancer vaccines for HLA-A26-positive cancer patients. The objective of this study was to identify peptide vaccine candidates for HLA-A26-positive cancer patients. The HLA-A*2601-crossbinding activity of 24 peptides currently under clinical trial as vaccines for HLA-A2, -A24, or HLA-A3 supertype-positive cancer patients was evaluated by stabilization assay. Three peptides with HLA-A2-binding activity could bind the HLA-A*2601 molecule. These three peptides induced HLA-A26-restricted cytotoxic T lymphocytes from HLA-A*2601-, -A*2602-, or -A*2603-positive prostate cancer patients against HLA-A*2601- and HLA-A*2603-positive cancer cells in CD8-dependent and peptide-specific manners. In addition, one peptide with HLA-A24-binding activity could bind to HLA-A*2601 and induced HLA-A26-restricted cytotoxic T lymphocytes from HLA-A*2601-, -A*2602-, or -A*2603-positive prostate cancer patients against HLA-A*2603-positive cancer cells. These results may provide novel information for the development of a peptide-based cancer vaccine for HLA-A26-positive patients.