Differential presentation of tumor antigen-derived epitopes by MHC-class I and antigen-positive tumor cells

Abstract

SSX2 is a member of the family of cancer/testis antigens. The SSX2 derived peptide SSX2103-111 has been shown to be presented to cytotoxic T-lymphocytes (CTL) by Major-Histocompatibility (MHC) Class-I complexes after endogenous processing, more precisely by the allele HLA-A*0201. The HLA-A*0201- and SSX2-positive melanoma cell line SK-Mel-37 but not Me275 had been shown to elicit reactivity in SSX2103-111 specific cytotoxic T-lymphocytes. To analyze the correlation between SSX2103-111 presentation and T-cell stimulation, we intended to visualize presentation of SSX2103-111 in these melanoma cell lines. Fab-antibodies were established from a human phage library with specificity for SSX2 103-111/HLA-A*0201 complexes (but non-reactive with HLA-A*0201 or SSX2103_111 alone) and used to visualize the presentation of SSX2103-111 in the context of HLA-A*0201 by fluorescence microscopy. Presentation of SSX2103-111 the context of HLA-A*0201 was demonstrated for the majority of SK-Mel-37, but for only a small fraction (<1%) of Me275 as indicated by a clear membrane-staining pattern in fluorescence microscopy. The presentation of SSX2103-111 on SK-Me137 and Me275, but not the expression of the SSX2 protein correlated with the capability of these cells to stimulate cells of an SSX2 103-111-specific T-cell clone. MHC-peptide specific antibodies are a valuable tool for the analysis of antigenic peptides in the context of MHC-I molecules and for the structural definition of immunodominant epitopes. © 2008 Wiley-Liss, Inc.