GENERATION OF CYTOTOXIC T-CELL RESPONSES WITH SYNTHETIC MELANOMA-ASSOCIATED PEPTIDES IN-VIVO - IMPLICATIONS FOR TUMOR VACCINES WITH MELANOMA-ASSOCIATED ANTIGENS

Peptide epitopes derived from differentiation antigens of the melanocy te lineage have been identified in human melanomas and normal cultured melanocytes as targets for MHC-restricted cytotoxic T lymphocytes (CT L). Characterization of multiple CTL-defined antigenic determinants an d the presence of corresponding precursor CTL open perspectives for th e development of antigen-based vaccines. In the present study, we dete rmined the CTL reactivity against melanoma-associated peptides derived from Melan A/MART-1, tyrosinase and gp100/Pme117 in 10 HLA-A2(+) mela noma patients and 10 healthy individuals. Then, we examined the immuno logical effects and toxicity of intradermal inoculation of synthetic m elanoma-associated peptides. Six patients with advanced melanoma recei ved weekly intradermal injections of 6 melanoma-associated peptides an d the influenza matrix peptide as a control for 4 consecutive weeks. D TH reactions were observed in 5/6 patients at the injection sites of t he tyrosinase signal peptide and of the influenza matrix peptide. No t oxic side effects were observed. Changes in CTL reactivity after pepti de vaccination were assessed by an MLPC assay for each peptide. Genera tion of peptide-specific CTL was documented against Melan A/MART-1-der ived peptide epitopes, the tyrosinase signal peptide and the influenza matrix peptide after vaccination; A decreasing CTL response against t he internal tyrosinase peptide was documented in I patient through the course of vaccination and a decrease in DTH reactions. No major tumor regressions were observed. Two patients with rapidly progressive dise ase before vaccination have shown disease stabilization since vaccinat ions started. In conclusion, our results demonstrate that peptide alon e injected intradermally may generate antigen-specific DTH reactions a nd an increase of antigen-specific CTL reactivity. (C) 1996 Wiley-Liss , Inc.