Spontaneous CD8 T cell responses against the melanocyte differentiation antigen RAB38/NY-MEL-1 in melanoma patients

SM Walton, M Gerlinger, O de la Rosa… - The Journal of …, 2006 - journals.aai.org
SM Walton, M Gerlinger, O de la Rosa, N Nuber, A Knights, A Gati, M Laumer, L Strauss
The Journal of Immunology, 2006journals.aai.org
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 …
Abstract
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-1 50–58 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-1 50–58 peptide. Accordingly, monoclonal RAB38/NY-MEL-1 50–58-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-1 50–58 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-1 50–58 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.
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