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Purpose: NY-ESO-1 (ESO), a tumor-specific antigen of the cancer/testis group, is presently viewed as an important model antigen for the development of generic anticancer vaccines. The ESO(119-143) region is immunodominant following immunization with a recombinant ESO vaccine. In this study, we generated DRB1*0101/ESO(119-143) tetramers and used them to assess CD4 T-cell responses in vaccinated patients expressing DRB1*0101 (DR1)., Experimental Design: We generated tetramers of DRB1*0101 incorporating peptide ESO(119-143) using a previously described strategy. We assessed ESO(119-143)-specific CD4 T cells in peptide-stimulated postvaccine cultures using the tetramers. We isolated DR1/ESO(119-143) tetramer(+) cells by cell sorting and characterized them functionally. We assessed vaccine-induced CD4(+) DR1/ESO(119-143) tetramer(+) T cells ex vivo and characterized them phenotypically., Results: Staining of cultures from vaccinated patients with DR1/ESO(119-143) tetramers identified vaccine-induced CD4 T cells. Tetramer(+) cells isolated by cell sorting were of T(H)1 type and efficiently recognized full-length ESO. We identified ESO(123-137) as the minimal optimal epitope recognized by DR1-restricted ESO-specific CD4 T cells. By assessing DR1/ESO(119-143) tetramer(+) cells using T cell receptor (TCR) β chain variable region (Vβ)-specific antibodies, we identified several frequently used Vβ. Finally, direct ex vivo staining of patients' CD4 T cells with tetramers allowed the direct quantification and phenotyping of vaccine-induced ESO-specific CD4 T cells., Conclusions: The development of DR1/ESO(119-143) tetramers, allowing the direct visualization, isolation, and characterization of ESO-specific CD4 T cells, will be instrumental for the evaluation of spontaneous and vaccine-induced immune responses to this important tumor antigen in DR1-expressing patients., (©2010 AACR.)

Purpose: ESO is a tumor-specific antigen with wide expression in human tumors of different histologic types and remarkable spontaneous immunogenicity. We have previously shown that specific T(H)1 and antibody responses can be elicited in patients with no detectable preexisting immune responses by vaccination with rESO administered with Montanide ISA-51 and CpG ODN 7909. The purpose of the present study was to characterize vaccine-induced ESO-specific CD4(+) T cell responses., Experimental Design: We generated CD4(+) T cell clones from patient C2, who had the highest CD4(+) T cell response to the vaccine, and analyzed their fine specificity and HLA class II restriction to determine the recognized epitope. We then assessed the response to the identified epitope in all vaccinated patients expressing the corresponding HLA class II allele., Results: We found that ESO-specific CD4(+) T cell clones from patient C2 recognize peptide ESO(119-143) (core region 123-137) presented by HLA-DR52b (HLA-DRB3*0202), a MHC class II allele expressed by about half of Caucasians. Importantly, following vaccination, all patients expressing DR52b developed significant responses to the identified epitope, accounting for, on average, half of the total CD4(+) T cell responses to the 119-143 immunodominant region. In addition, analysis of ESO-specific DR52b-restricted CD4(+) T cells at the clonal level revealed significant conservation of T cell receptor usage among different individuals., Conclusions: The identification of a DR52b-restricted epitope from ESO that is immunodominant in the context of vaccine-elicited immune responses is instrumental for the immunologic monitoring of vaccination trials targeting this important tumor antigen.

In a recent vaccination trial assessing the immunogenicity of an NY-ESO-1 (ESO) recombinant protein administered with Montanide and CpG, we have obtained evidence that this vaccine induces specific cytolytic T lymphocytes (CTL) in half of the patients. Most vaccine-induced CTLs were directed against epitopes located in the central part of the protein, between amino acids 81 and 110. This immunodominant region, however, is distinct from another ESO CTL region, 157-165, that is a frequent target of spontaneous CTL responses in A2+ patients bearing ESO tumors. In this study, we have investigated the CTL responses to ESO 157-165 in A2+ patients vaccinated with the recombinant protein. Our data indicate that after vaccination with the protein, CTL responses to ESO 157-165 are induced in some, but not all, A2+ patients. ESO 157-165-specific CTLs induced by vaccination with the ESO protein were functionally heterogeneous in terms of tumor recognition and often displayed decreased tumor reactivity as compared with ESO 157-165-specific CTLs isolated from patients with spontaneous immune responses to ESO. Remarkably, protein-induced CTLs used T-cell receptors similar to those previously isolated from patients vaccinated with synthetic ESO peptides (Vbeta4.1) and distinct from those used by highly tumor-reactive CTLs isolated from patients with spontaneous immune responses (Vbeta1.1, Vbeta8.1, and Vbeta13.1). Together, these results demonstrate that vaccination with the ESO protein elicits a repertoire of ESO 157-165-specific CTLs bearing T-cell receptors that are structurally distinct from those of CTLs found in spontaneous immune responses to the antigen and that are heterogeneous in terms of tumor reactivity, being often poorly tumor reactive.

Purpose: Vaccination with full-length human tumor antigens aims at inducing or increasing antitumor immune responses, including CD8 CTL in cancer patients across the HLA barrier. We have recently reported that vaccination with a recombinant tumor-specific NY-ESO-1 (ESO) protein, administered with Montanide and CpG resulted in the induction of specific integrated antibody and CD4 T cell responses in all vaccinated patients examined, and significant CTL responses in half of them. Vaccine-induced CTL mostly recognized a single immunodominant region (ESO 81-110). The purpose of the present study was to identify genetic factor(s) distinguishing CTL responders from nonresponders., Experimental Design: We determined the HLA class I alleles expressed by CTL responders and nonresponders using high-resolution molecular typing. Using short overlapping peptides spanning the ESO immunodominant CTL region and HLA class I/ESO peptide tetramers, we determined the epitopes recognized by the majority of vaccine-induced CTL., Results: CTL induced by vaccination with ESO protein mostly recognized distinct but closely overlapping epitopes restricted by a few frequently expressed HLA-B35 and HLA-Cw3 alleles. All CTL responders expressed at least one of the identified alleles, whereas none of the nonresponders expressed them., Conclusions: Expression of HLA-B35 and HLA-Cw3 is associated with the induction of immunodominant CTL responses following vaccination with recombinant ESO protein. Because recombinant tumor-specific proteins are presently among the most promising candidate anticancer vaccines, our findings indicate that the monitoring of cancer vaccine trials should systematically include the assessment of HLA association with responsiveness.

Expression of the cancer/germ-line antigen NY-ESO-1 by tumors elicits spontaneous humoral and cellular immune responses in some cancer patients. Development of vaccines capable of stimulating such comprehensive immune responses is desirable. We have produced recombinant lentivectors directing the intracellular synthesis of NY-ESO-1 (rLV/ESO) and have analyzed the in vivo immune response elicited by this vector. Single injection of rLV/ESO into HLA-A2-transgenic mice elicited long-lasting B and T cell responses against NY-ESO-1. CD8+ T cells against the HLA-A2-restricted peptide NY-ESO-1(157-165) were readily detectable ex vivo and showed restricted TCR Vbeta usage. Moreover, rLV/ESO elicited a far greater anti-NY-ESO-1(157-165) CD8+ T cell response than peptide- or protein-based vaccines. Anti-NY-ESO-1 antibodies were rapidly induced after immunization and their detection preceded that of the antigen-specific CD8+ T cells. The rLV/ESO also induced CD4+ T cells. These cells played an essential role as their depletion completely abrogated B cell and CD8+ T cell responses against NY-ESO-1. The induced CD4+ T cells were primarily directed against a single NY-ESO-1 epitope spanning amino acids 81-100. Altogether, our study shows that rLV/ESO induces potent and comprehensive immune responses in vivo.

NY-ESO-1 is a cancer/testis antigen expressed in a range of human malignancies, and a number of vaccine strategies targeting NY-ESO-1 are being developed. In the present study, the safety and immunogenicity of recombinant vaccinia-NY-ESO-1 and recombinant fowlpox-NY-ESO-1 were analyzed in a series of 36 patients with a range of different tumor types. Each construct was first tested individually at two different dose levels and then in a prime-boost setting with recombinant vaccinia-NY-ESO-1 followed by recombinant fowlpox-NY-ESO-1. The vaccines were well tolerated either individually or together. NY-ESO-1-specific antibody responses and/or specific CD8 and CD4 T cell responses directed against a broad range of NY-ESO-1 epitopes were induced by a course of at least four vaccinations at monthly intervals in a high proportion of patients. CD8 T cell clones derived from five vaccinated patients were shown to lyse NY-ESO-1-expressing melanoma target cells. In several patients with melanoma, there was a strong impression that the natural course of the disease was favorably influenced by vaccination.

Spontaneous immune responses to the cancer testis antigen NY-ESO-1 are frequently found in cancer patients bearing antigen-expressing tumors. In HLA-A2-expressing patients, naturally elicited NY-ESO-1-specific, tumor-reactive cytotoxic T lymphocytes (CTLs) are mostly directed against an immunodominant epitope corresponding to peptide NY-ESO-1 157-165. NY-ESO-1-specific CTLs can also be induced by synthetic peptide vaccines, but they are heterogeneous in terms of functional avidity and tumor reactivity. The authors investigated the structural bases of this phenomenon by analyzing the TCR features of natural and vaccine-induced NY-ESO-1-specific CTLs. The results indicate that CTLs from the two groups exhibit highly structurally conserved but distinct TCR features, suggesting that the synthetic peptides used for vaccination may fail to faithfully mimic the naturally processed antigen. Together, the results of this study underline the strength of TCR molecular monitoring and will be instrumental for the development and monitoring of vaccines aimed at eliciting CTLs with high tumor reactivity.

The purpose of this study was to test melanoma vaccines consisting of peptides and immunological adjuvants for optimal immunogenicity and to evaluate laboratory immune monitoring for in vivo relevance. Forty-nine HLA-A2 positive patients with Melan-A positive melanoma were repeatedly vaccinated with Melan-A peptide, with or without immune adjuvant AS02B (QS21 and MPL) or IFA. Peptide-specific CD8 T cells in PBLs were analyzed ex vivo using fluorescent HLA-A2/Melan-A multimers and IFN-gamma ELISPOT assays. The vaccines were well tolerated. In vivo expansion of Melan-A-specific CD8 T cells was observed in 13 patients (1/12 after vaccination with peptide in AS02B and 12/17 after vaccination with peptide in IFA). The T cells produced IFN-gamma and downregulated CD45RA and CD28. T-cell responses correlated with inflammatory skin reactions at vaccine injection sites (P < 0.001) and with DTH reaction to Melan-A peptide (P < 0.01). Twenty-six of 32 evaluable patients showed progressive disease, whereas 4 patients had stable disease. The two patients with the strongest Melan-A-specific T-cell responses experienced regression of metastases in skin, lymph nodes, and lung. We conclude that repeated vaccination with Melan-A peptide in IFA frequently leads to sustained responses of specific CD8 T cells that are detectable ex vivo and correlate with inflammatory skin reactions.

Ectopic gene expression in tumors versus normal somatic tissues provides opportunities for the specific immunotargeting of cancer cells. SSX gene products are expressed in tumors of different histological types and can be recognized by tumor-reactive CTLs from cancer patients. Here, we report the identification of an SSX-2-derived immunodominant T cell epitope recognized by CD4(+) T cells from melanoma patients in association with HLA-DR. The epitope maps to the 37-58 region of the protein, encompassing the sequence of the previously defined HLA-A2-restricted immunodominant epitope SSX-2(41-49). SSX-2(37-58)-specific CD4(+) T cells were detected among circulating lymphocytes from the majority of melanoma patients analyzed and among tumor-infiltrating lymphocytes, but not in healthy donors. Together, our data suggest a dominant role of the 37-58 sequence in the induction of cellular CD4(+) T cell responses against SSX antigens and will be instrumental for both the onset and the monitoring of upcoming cancer-vaccine trials using SSX-derived immunogens.

The recent identification and molecular characterization of tumor-associated antigens recognized by tumor-reactive CD8+ T lymphocytes has led to the development of antigen-specific immunotherapy of cancer. Among other approaches, clinical studies have been initiated to assess the in vivo immunogenicity of tumor antigen-derived peptides in cancer patients. In this study, we have analyzed the CD8+ T cell response of an ocular melanoma patient to a vaccine composed of four different tumor antigen-derived peptides administered simultaneously in incomplete Freund's adjuvant (IFA). Peptide NY-ESO-1(157-165) was remarkably immunogenic and induced a CD8+ T cell response detectable ex vivo at an early time point of the vaccination protocol. A CD8+ T cell response to the peptide analog Melan-A(26-35 A27L) was also detectable ex vivo at a later time point, whereas CD8+ T cells specific for peptide tyrosinase(368-376) were detected only after in vitro peptide stimulation. No detectable CD8+ T cell response to peptide gp100(457-466) was observed. Vaccine-induced CD8+ T cell responses declined rapidly after the initial response but increased again after further peptide injections. In addition, tumor antigen-specific CD8+ T cells were isolated from a vaccine injection site biopsy sample. Importantly, vaccine-induced CD8+ T cells specifically lysed tumor cells expressing the corresponding antigen. Together, these data demonstrate that simultaneous immunization with multiple tumor antigen-derived peptides can result in the elicitation of multiepitope-directed CD8+ T cell responses that are reactive against antigen-expressing tumors and able to infiltrate antigen-containing peripheral sites.

The efficacy of current standard therapies for the treatment of sarcoma remains limited. With the aim of identifying target antigens relevant to the development of vaccine-based immunotherapy of sarcoma, we have addressed the relevance of tumor-specific antigens encoded by genes belonging to the SSX family as vaccine targets in sarcoma tumors. Expression of SSX-1 to -5 was analyzed in a collection of sarcoma tumors of diverse histological subtypes and in sarcoma cell lines. We found expression of at least one SSX-encoded antigen in 42% of sarcoma tumors, including 5 of 7 different histological subtypes, and in 50% of sarcoma cell lines. SSX-1 was the most frequently expressed family member, followed by SSX-4, -2 and -5. Expression of SSX-3 was detected in only one sample. Importantly, most SSX positive samples co-expressed more than one family member. In addition, assessment of CD8+ T cell recognition of HLA-A2+ SSX-2+ sarcoma cells showed that the latter were efficiently recognized and lysed by SSX-2-specific CTLs. The results of this study indicate that SSX antigens are relevant targets for the development of vaccine-based immunotherapy of sarcoma and encourage the start of vaccination trials using SSX-derived immunogens in sarcoma patients.

Purpose: As compared with natural tumor peptide sequences, carefully selected analog peptides may be more immunogenic and thus better suited for vaccination. However, T cells in vivo activated by such altered analog peptides may not necessarily be tumor specific because sequence and structure of peptide analogs differ from corresponding natural peptides., Experimental Design: Three melanoma patients were immunized with a Melan-A peptide analog that binds more strongly to HLA-A*0201 and is more immunogenic than the natural sequence. This peptide was injected together with a saponin-based adjuvant, followed by surgical removal of lymph node(s) draining the site of vaccination., Results: Ex vivo analysis of vaccine site draining lymph nodes revealed antigen-specific CD8+ T cells, which had differentiated to memory cells. In vitro, these cells showed accelerated proliferation upon peptide stimulation. Nearly all (16 of 17) of Melan-A-specific CD8+ T-cell clones generated from these lymph nodes efficiently killed melanoma cells., Conclusions: Patient immunization with the analog peptide leads to in vivo activation of T cells that were specific for the natural tumor antigen, demonstrating the usefulness of the analog peptide for melanoma immunotherapy.

Abstract: Because of its frequent expression in tumors and spontaneous immunogenicity in advanced cancer patients, NY-ESO-1 is presently viewed as a prototype tumor antigen for the development of cancer vaccines. A prerequisite for the analysis of NY-ESO-1-specific T cell responses in vaccinated patients is the assessment of the complete T cell repertoire available for the antigen. Here, we have assessed frequency and fine specificity of CD4+ T cells reactive against NY-ESO-1-derived sequences in circulating lymphocytes from cancer patients with spontaneous responses to the antigen. We found that, relative to healthy donors, this frequency was only moderately increased in cancer patients. The reactivity of these cells, however, was directed against the same immunodominant regions previously identified for healthy donors. On account of these data, we developed an approach for the immune monitoring of NY-ESO-1-specific CD4+ T cell responses based on the assessment of CD4+ T cell populations of defined phenotype. Using this approach, a similar frequency of NY-ESO-1-specific CD4+ T cells was found among naive T cells of healthy donors and cancer patients. In contrast, among antigen-experienced T cells, NY-ESO-1-specific CD4+ T cells were exclusively detectable in cancer patients. We anticipate that this phenotype-based approach will be useful for the immune monitoring of vaccine-induced responses in vaccination trials using NY-ESO-1 as well as other tumor antigens. [Copyright &y& Elsevier]