Binding, presentation and immunogenicity of peptides derived from melanoma antigens MART1 and GPZOO by HLA-A2 subtypes

HLA-A0201-restricted melanoma-reactive CTL responses have been extensively studied; this allele is widely expressed among Caucasians, a group at risk for melanoma. We observed an unexpectedly high frequency ( 20%) of non-HLA-A0201 allelic variants (including 0205, "0204 and 0202) in a group of Italian melanoma patients. In the present study we analyzed peptide presentation by different HLA-A2 subtypes using melanoma-derived epitopes MART-l(27-35) , G9-154 and G9-280, and Flu-Ml(58-66). These peptides bound to most of the subtypes tested with IC50 values less than 500 nM, though instances of very poor binding were also noted. HLA-A0201restricted CTL displayed a limited ability to recognize peptide-pulsed EBV-B cell lines expressing different subtype molecules. Patterns of recognition varied with the peptides and effectors tested. In immunogenicity experiments, only anti-G9-280 CTL could be generated from PBL of 3β HLA-A0205 melanoma patients by in vitro peptide sensitization, while only anti-FluMl(58-66) CTL were induced in 2/2 HLA-A0202 subjects. Anti-G9-280 specific CTL recognized HLA-A0205 melanoma cells, indicating that this epitope is endogenously presented. These data imply .the necessity of subtyping patients undergoing peptide-based protocols and underline the need for additional studies of melanoma-directed T cell responses among patients expressing non-HLAA0201 subtypes.