In vitro stimulation of CD8 and CD4 T cells by dendritic cells loaded with a complex of cholesterol-bearing hydrophobized pullulan and NY-ESO-1 protein: Identification of a new HLA-DR15-binding CD4 T-cell epitope

Purpose: NY-ESO-1 belongs to a class of cancer/testis antigens and has been shown to be immunogenic in cancer patients. We synthesized a complex of cholesterol-bearing hydrophobized pullulan and NY-ESO-1 protein (CHP/ESO) and investigated the in vitro stimulation of CD8 and CD4 T cells from peripheral blood mononuclear cells in healthy donors with autologous CHP/ESO-loaded dendritic cells as antigen-presenting cells. Experimental Design: In vitro stimulation of CD8 or CD4 T cells was determined by IFNγ ELISPOT assays against autologous EBV-B cells infected with vaccinia/NY-ESO-1 recombinant virus or wild-type vaccinia virus as targets and by ELISA measuring secreted IFNγ Results: NY-ESO-1-specific CD8 and CD4 T cells were induced. In a donor expressing HLA-A2, CD8 T cells stimulated with CHP/ESO-loaded dendritic cells recognized naturally processed NY-ESO-1_157-165, an HLA-A2-binding CD8 T cell epitope. NY-ESO-1 CD4 T cells were TH1-type. We identified a new HLA-DR15- binding CD4 T cell epitope, NY-ESO-1_37.50. Conclusions: These findings indicate that CHP/ESO is a promising polyvalent cancer vaccine targeting NY-ESO-1.