Synthesis and antigenic properties of reduced peptide bond analogues of an immunodominant epitope of the melanoma MART-1 protein.

Backbone modifications have been introduced into the melanoma derived peptide MART-1(27-35) to increase its binding to class I major histocompatibility complex HLA-A2 molecule, and ultimately to enhance its immunogenicity. Each analogue was obtained by replacing one peptide bond at a time in the natural epitope by the aminomethylene (CH2-NH) surrogate. All analogues displayed an increased resistance to proteolysis. Interestingly, the comparative results showed that five analogues bound more efficiently to HLA-A2 than the parent peptide. On the other hand, two pseudopeptide/HLA-A2 complexes were recognized by one melanoma-specific T cell clone. Close examination of the impact of such modifications at the molecular level provides useful supports for the rational design of stable compounds with applications in anti-tumour specific immunotherapy and in vaccine development.