INTRALESIONAL SELECTION OF T-CELL CLONOTYPES IN THE IMMUNE-RESPONSE TO MELANOMA ANTIGENS OCCURRING DURING VACCINATION

T cells infiltrating pre- and postvaccine metastases obtained from mel anoma patients vaccinated with either dinitrophenyl (DNP)-modified aut ologous tumor or with the MAGE-3.Al peptide display selective T cell r eceptor (TCR) beta chain variable region (BV) repertoire changes at th e tumor site as a consequence of vaccination. Restricted sets of BV fa milies expand in all postvaccine lesions when compared with prevaccine specimens and often contain dominant clones. A protocol devised to ob tain T cell lines highly enriched for expression of a given BV region through the use of anti-EV monoclonal antibodies was used to understan d whether responses to specific antigen(s) accounted for these clonal expansions. In one of the patients vaccinated with DNP-modified tumor cells, BV-driven selection of the T lymphocytes expanded in two infilt rated postvaccine metastases resulted in T cell lines able to exert HL A class I-restricted lysis of the autologous tumor. These results indi cate that TCR repertoire analysis at the tumor site facilitates the de tection of T cell responses elicited by a vaccine and potentially cyto toxic for the autologous tumor.