Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

Abstract

Abstract The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)–A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c+ blood DCs cross-presented NY-ESO-1–specific HLA-A2157-165–, HLA-B760-72–, and HLA-Cw392-100–restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1157-165/HLA-A2, NY-ESO-160-72/HLA-B7, and NY-ESO-192-100/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-160-72/HLA-B7–restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A–, B–, and C–restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.