A long peptide from MELOE-1 contains multiple HLA class II T cell epitopes in addition to the HLA-A*0201 epitope: An attractive candidate for melanoma vaccination

摘要

CD4 + T cells contribute importantly to the antitumor T cell response, and thus, long peptides comprising CD4 and CD8 epitopes may be efficient cancer vaccines. We have previously identified an overexpressed antigen in melanoma, MELOE-1, presenting a CD8 + T cell epitope, MELOE-1 36-44, in the HLA-A*0201 context. A T cell repertoire against this epitope is present in HLA-A*0201+ healthy subjects and melanoma patients and the adjuvant injection of TIL containing MELOE-1 specific CD8 + T cells to melanoma patients was shown to be beneficial. In this study, we looked for CD4 + T cell epitopes in the vicinity of the HLA-A*0201 epitope. Stimulation of PBMC from healthy subjects with MELOE-1 26-46 revealed CD4 responses in multiple HLA contexts and by cloning responsive CD4 + T cells, we identified one HLA-DRβ1*1101-restricted and one HLA-DQβ1*0603-restricted epitope. We showed that the two epitopes could be efficiently presented to CD4 + T cells by MELOE-1-loaded dendritic cells but not by MELOE-1+ melanoma cell-lines. Finally, we showed that the long peptide MELOE-1 22-46, containing the two optimal class II epitopes and the HLA-A*0201 epitope, was efficiently processed by DC to stimulate CD4 + and CD8 + T cell responses in vitro, making it a potential candidate for melanoma vaccination.