T-helper cell-response to MHC class II-binding peptides of the renal cell carcinoma-associated antigen RAGE-1

Recently, epitope prediction software for HLA-DR binding sequences has become available. In view of the importance of T helper (Th) cell activation in immunotherapy of cancer and evidences supporting immunogenicity of renal cell carcinoma (RCC), we have tested 4 peptides of RAGE-1 binding promiscuously to HLA-DR molecules for induction of an immune response. The peptides predicted by the TEPITOPE program using a stringent threshold were derived from the open reading frame 2 and 5 of RAGE-1. Induction of response was evaluated by culturing peripheral blood mononuclear cells (PBMC) in the presence of peptide-loaded dendritic cells (DC) to determine proliferative activity and cytokine expression. Two out of 5 donors did not respond to any of the 4 peptides, 2 donors responded to one peptide and one donor responded to two other peptides. Notably, as revealed by blocking studies and T cell subtype definition, peptides bound to MHC class II molecules and peptide pulsed DC exclusively activated CD4+ T cells, which were of the Th1 subtype. With respect to clinical application it is important that (un)responsiveness of individual donors' PBMC was a very consistent feature. Though we have not tested explicitly whether these peptides correspond to naturally processed peptides, the possibility to define those patients whose Th might respond to in silico predicted peptides of RAGE-1, by an in vitro assay, could well be a helpful step towards setting up a RAGE-1 based immunotherapeutic protocol.