PEPTIDE-PULSED DENDRITIC CELLS INDUCE TUMORICIDAL CYTOTOXIC T-LYMPHOCYTES FROM HEALTHY DONORS AGAINST STABLY HLA-A-ASTERISK-0201-BINDING PEPTIDES FROM THE MELAN-A MART-1 SELF ANTIGEN/

The melanoma antigen Melan-A/MART-1 was screened for the presence of p otential HLA-A0201-binding cytotoxic T lymphocytes (CTL) epitopes. Th e immunodominant nonamer epitope AAGIGILTV demonstrated weak binding t o T2 but a significant half-life of binding to HLA-A0201 in contrast to the decamer EAAGIGILTV. In addition to the immunodominant CTL epito pe, we describe two peptides, GILTVILGV and ALMDKSLHV, that display st able binding to HLA-A0201. Using cultured autologous dendritic cells pulsed with these peptides, CTL lines were induced from peripheral blo od lymphocytes that displayed reactivity with HLA-A2(+), Melan-A/MART- 1(+) melanoma cells. CTL reactivity against the immunodominant epitope could be induced with the nonamer epitope alone, but not with the dec amer variant. CTL clones generated from an (EAAGIGILTV + AAGIGILTV)-in duced CTL line recognize the appropriate melanoma cells and normal mel anocytes. Upon further characterization of one of these CTL clones, it was found to be of surprisingly high affinity considering that it is directed against a self antigen. This study demonstrates that immunoge nic peptides can be selected based on stability (half-life) of peptide / HLA binding. In addition, cultured DC were found to efficiently indu ce CTL responses in vitro against such selected peptides, and some of these CTL were capable of recognizing endogenously processed antigen.