Identificaiton of Novel Immunogenic Human Papillomavirus Type 16 E7-Specific Epitopes Restricted to HLA-A(*)33;03 for Cervical Cancer Immunotherapy

PURPOSE: To identify new immunogenic HLA-A(*)33;03-restricted epitopes from the human papillomavirus (HPV) 16 E7 protein for immunotherapy against cervical cancer. MATERIALS AND METHODS: We synthesized fourteen overlapping 15-amino acid peptides and measured intracellular interferon-γ (IFN-γ) production in PBMC and CD8+ cytotoxic T lymphocytes (CTLs) after sensitization with these peptides using flow cytometry and ELISpot assay. The immunogenicity of epitopes was verified using a (51)Cr release assay with SNU1299 cells. RESULTS: Among the fourteen 15-amino acid peptides, E7(49-63) (RAHYNIVTFCCKCDS) demonstrated the highest IFN-γ production from peripheral blood mononuclear cells (PBMCs), and CD8+ CTLs sensitized with E7(49-63) showed higher cytotoxic effect against SNU1299 cells than did CD8+ CTLs sensitized with other peptides or a negative control group. Thirteen 9- or 10-amino acid overlapping peptides spanning E7(49-63), E7(50-59) (AHYNIVTFCC), and E7(52-61) (YNIVTFCCKC) induced significantly higher IFN-γ production and cytotoxic effects against SNU1299 cells than the other peptides and negative controls, and the cytotoxicity of E7(50-59)- and E7(52-61)-sensitized PBMCs was induced via the cytolytic effect of CD8+ CTLs. CONCLUSION: We identified E7(50-59) and E7(52-61) as novel HPV 16 E7 epitopes for HLA-A(*)33;03. CD8+ CTL sensitized with these peptides result in an antitumor effect against cervical cancer cells. These epitopes could be useful for immune monitoring and immunotherapy for cervical cancer and HPV 16-related diseases including anal cancer and oropharyngeal cancer.