Natko Nuber

Rational development of high-affinity T-cell receptor-like antibodies

T-cell interaction with a target cell is a key event in the adaptive immune response and primarily driven by T-cell receptor (TCR) recognition of peptide-MHC (pMHC) complexes. TCR avidity for a given pMHC is determined by number of MHC molecules, availability of coreceptors, and TCR affinity for MHC or peptide, respectively, with peptide recognition being the most important factor to confer target specificity. Here we present high-resolution crystal structures of 2 Fab antibodies in complex with the immunodominant NY-ESO-1157–165 peptide analogue (SLLMWITQV) presented by HLA-A*0201 and compare them with a TCR recognizing the same pMHC. Binding to the central methionine-tryptophan peptide motif and orientation of binding were almost identical for Fabs and TCR. As the MW “peg” dominates the contacts between Fab and peptide, we estimated the contributions of individual amino acids between the Fab and peptide to provide the rational basis for a peptide-focused second-generation, high-affinity antibody library. The final Fab candidate achieved better peptide binding by 2 light-chain mutations, giving a 20-fold affinity improvement to 2–4 nM, exceeding the affinity of the TCR by 1,000-fold. The high-affinity Fab when grafted as recombinant TCR on T cells conferred specific killing of HLA-A*0201/NY-ESO-1157–165 target cells. In summary, we prove that affinity maturation of antibodies mimicking a TCR is possible and provide a strategy for engineering high-affinity antibodies that can be used in targeting specific pMHC complexes for diagnostic and therapeutic purposes.

Expression of MAGE-C1/CT7 and MAGE-C2/CT10 predicts lymph node metastasis in melanoma patients.

MAGE-C1/CT7 and MAGE-C2/CT10 are members of the large MAGE family of cancer-testis (CT) antigens. CT antigens are promising targets for immunotherapy in cancer because their expression is restricted to cancer and germ line cells and a proportion of cancer patients presents with immune responses against CT antigens, which clearly demonstrates their immunogenicity. This study investigates the expression of MAGE-C1/CT7 and MAGE-C2/CT10 in primary and metastatic melanoma. Immunohistochemical staining of tissue microarrays that consisted of 59 primary malignant melanomas of the skin, 163 lymph node and distant melanoma metastases and 68 melanoma cell lines was performed. We found MAGE-C1/CT7 expression in 15 out of 50 (24%) primary melanomas and 15 out of 50 (24%) cell lines, whereas MAGE-C2/CT10 was detected in 17 out of 51 (33%) primary melanomas and 14 out of 68 (17%) cell lines. MAGE-C1/CT7 and MAGE-C2/CT10 were both detected in 40% of melanoma metastases. Patients with MAGE-C1/CT7 or MAGE-C2/CT10 positive primary melanoma had significantly more lymph node metastases (p = 0.005 and p<0.001, resp.). Prediction of lymph node metastasis by MAGE-C1/CT7 and MAGE-C2/CT10 was independent of tumor cell proliferation rate (Ki67 labeling index) in a multivariate analysis (p = 0.01). Our results suggest that the expression of MAGE-C1/CT7 and MAGE-C2/CT10 in primary melanoma is a potent predictor of sentinel lymph node metastasis.

MAGE-C1/CT7 is the dominant cancer-testis antigen targeted by humoral immune responses in patients with multiple myeloma

MAGE-C1/CT7 is the dominant cancer-testis antigen targeted by humoral immune responses in patients with multiple myeloma

Spontaneous CD8 T Cell Responses against the Melanocyte Differentiation Antigen RAB38/NY-MEL-1 in Melanoma Patients

The melanocyte differentiation Ag RAB38/NY-MEL-1 was identified by serological expression cloning (SEREX) and is expressed in the vast majority of melanoma lesions. The immunogenicity of RAB38/NY-MEL-1 has been corroborated previously by the frequent occurrence of specific Ab responses in melanoma patients. To elucidate potential CD8 T cell responses, we applied in vitro sensitization with overlapping peptides spanning the RAB38/NY-MEL-1 protein sequence and the reverse immunology approach. The identified peptide RAB38/NY-MEL-150–58 exhibited a marked response in ELISPOT assays after in vitro sensitization of CD8 T cells from HLA-A∗0201+ melanoma patients. In vitro digestion assays using purified proteasomes provided evidence of natural processing of RAB38/NY-MEL-150–58 peptide. Accordingly, monoclonal RAB38/NY-MEL-150–58-specific T cell populations were capable of specifically recognizing HLA-A2+ melanoma cell lines expressing RAB38/NY-MEL-1. Applying fluorescent HLA-A2/RAB38/NY-MEL-150–58 multimeric constructs, we were able to document a spontaneously developed memory/effector CD8 T cell response against this peptide in a melanoma patient. To elucidate the Ag-processing pathway, we demonstrate that RAB38/NY-MEL-150–58 is produced efficiently by the standard proteasome and the immunoproteasome. In addition to the identification of a RAB38/NY-MEL-1-derived immunogenic CD8 T cell epitope, this study is instrumental for both the onset and monitoring of future RAB38/NY-MEL-1-based vaccination trials.

Fine analysis of spontaneous MAGE-C1/CT7–specific immunity in melanoma patients

Cancer/testis (CT) antigens represent prime candidates for immunotherapy in cancer patients, because their expression is restricted to cancer cells and germ cells of the testis. MAGE-C1/CT7 is a CT antigen that is highly expressed in several types of cancers. Spontaneous occurrence of CT7-specific antibodies was previously detected by SEREX screen in a melanoma patient. However, naturally occurring CT7-specific T-cell responses have thus far not been detected. Peripheral blood mononuclear cells (PBMCs) from 26 metastatic melanoma patients expressing CT7 in their tumor lesions (CT7+) were analyzed for CT7-specific T-cell responses using overlapping peptides. CT7-specific CD4+ T-cell responses were detected in three patients (11.5%). These CT7-specific CD4+ T-cell responses were detectable in melanoma patients’ PBMCs exclusively from preexisting CD45RA− memory CD4+ T-cell pool. Additional CT7-specific memory CD4+ T-cell responses were detected in CT7+ melanoma patients after depletion of CD4+CD25high Treg cells showing that Treg cells impact on CT7-specific CD4+ T cells in melanoma patients. CT7-specific CD4+ T-cell clones were generated and used to define minimal epitopes, restriction elements, and confirm the recognition of naturally processed antigen. Surprisingly, these clones were able to secrete perforin and exert cytotoxicity. This study shows that CT7 can induce specific cellular immunity in melanoma patients. Based on these findings, CT7 will be further explored as a potential vaccine for melanoma immunotherapy.

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.

Abstract 5530: Evidence for immunological pressure and escape from longitudinal analysis of the expression of and immune responses against NY-ESO-1 in a patient with metastatic melanoma

Rationale: Metastatic malignant melanoma patients have a median survival of 8.5 months and a probability of surviving 5 years after the diagnosis of less than 5%. Melanoma patients have been treated with immunotherapeutic approaches including vaccination which induced durable clinical responses in a small subset of patients. Here we present a thorough characterisation of a patient living almost 10 years with metastatic melanoma, who was treated with standard therapy followed by two anti-NY-ESO-1 vaccinations, surgeries and finally Ipilimumab. The patient (ZH-311) was closely immune monitored for the expression of NY-ESO-1 in the tumor and for NY-ESO-1 specific immune response during the course of disease. Methods: The clinical course of the patient was followed from the beginning of diagnosis (03/01) to his death in 07/10. NY-ESO-1-specific CD8+ T cell responses in peripheral blood mononuclear cells (PBMC) were analyzed by intracellular cytokine staining. Antibodies against NY-ESO-1 were monitored by ELISA. Each operated tumor and tumor site found in autopsy was analyzed for NY-ESO-1 by immunohistochemistry. Results: The clinical course of ZH-311 is remarkable, because he lived for more than 6y with immunotherapy and 5 surgical interventions for metastases. 4 surgeries were performed due to progressing disease and the liver metastasis were stable at the time of operation. The early lesions displayed strong NY-ESO-1 expression and a very strong, polyfunctional CD8+ T-cell response against NY-ESO-1 was observed before immunotherapy, which increased upon VF vaccination. The cellular response was mirrored by the antibody response. However, the NY-ESO-1-specific CD8+ T cell response decreased upon vaccination with NY-ESO-1 protein plus CpG, whereas the antibody response remained high for one more year. Examination of later lesions revealed a loss of NY-ESO-1 expression, which is suggestive of escape as a result of immunological pressure. Conclusion: Before and after the vaccination with NY-ESO-1 the patient had an integrated immune response with NY-ESO-1 including antibodies as well as polyfunctional CD8+ T cells. All tumors analysed after the anti-NY-ESO-1 vaccination were NY-ESO-1 negative, suggesting outgrowing escape variants. The stable liver metastases were NY-ESO-1 positive and were apparently immunologically controlled. The persisting antibody levels against NY-ESO-1 dropped after the excision of the NY-ESO-1+ liver metastasis, which suggests a correlation between antigen load and antibody titers. The study we present here provides direct clinical evidence for initial control and susbsequent sculpting of the tumor by the adaptive immune response. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5530. doi:10.1158/1538-7445.AM2011-5530