Melanoma peptide MART-1(27-35) analogues with enhanced binding capacity tothe human class I histocompatibility molecule HLA-A2 by introduction of a beta-amino acid residue: Implications for recognition by tumor-infiltratinglymphocytes

The design of heteroclytic antigens with high MHC binding capacity is of pa rticular interest to overcome the weak immunogenicity of peptide epitopes d erived from tissue antigens expressed by tumors. In the present study, doub le-substituted peptide analogues of the tumor-associated antigen MART-1(27- 35) incorporating a substitution at a primary anchor residue and a beta-ami no acid residue at different positions in the sequence were synthesized and evaluated for binding to the human histocompatibility class I molecule HLA -A2 and for recognition by tumorinfiltrating lymphocytes. Interestingly, by combining a Leu for Ala substitution at P2 (which alone is deleterious for antigenic activity) with a beta-amino acid substitution at a putative TCR contact residue, recognition by tumor-infiltrating lymphocytes was partiall y restored. The analogue [Leu(28),beta-HIle(30)]MART-1(27-35) displays both a higher affinity to HLA-A2 and a more prolonged complex stability compare d to [Leu28]MART-1(27-35). Overall, these results suggest that double-subst itution strategies and beta-amino acid replacements at putative TCR contact residues might prove useful for the design of epitope mimics with high MHC binding capacity.