Identification of NY-ESO-1 epitopes presented by human histocompatibility antigen (HLA)-DRB4*0101-0103 and recognized by CD4(+) T lymphocytes of patients with NY-ESO-1-expressing melanoma

NY-ESO-1 is a member of the cancer-testis family of tumor antigens that eli cits strong humoral and cellular immune responses in patients with NY-ESO-1 -expressing cancers. Since CD4(+) T lymphocytes play a critical role in gen erating antigen-specific cytotoxic T lymphocyte and antibody responses, eve searched for NY-ESO-1 epitopes presented by histocompatibility leukocyte a ntigen (HLA) class II molecules. Autologous monocyte-derived dendritic cell s of cancer patients were incubated with recombinant NY-ESO-1 protein and u sed in enzyme-linked immunospot (ELISPOT) assays to detect NY-ESO-1-specifi c CD4+ T lymphocyte responses. To identify possible epitopes presented by d istinct HLA class II alleles, overlapping 18-mer peptides derived from NY-E SO-1 were synthetized and tested for recognition by CD4(+) T lymphocytes in autologous settings. We identified three NY-ESO-1-derived peptides present ed by DRB4*0101-0103 and recognized by CD4(+) T lymphocytes of two melanoma patients sharing these HLA class II alleles. Specificity of recognition wa s confirmed by proliferation assays. The characterization of HLA class II-r estricted epitopes will be useful for the assessment of spontaneous and vac cine-induced immune responses of cancer patients against defined tumor anti gens. Further, the therapeutic efficacy of active immunization using antige nic HLA class I-restricted peptides may be improved by adding HLA class II- presented epitopes.