Identification of human papillomavirus 16-E6 protein-derived peptides with the potential to generate cytotoxic T-lymphocytes toward human leukocyte antigen-A241 cervical cancer

Human papillomavirus 16 (HPV16)-E6 and -E7 proteins are considered to be appropriate targets in specific immunotherapy for cervical cancer. In this study, we attempted to identify epitope peptides from the HPV16-E6 protein that have the potential to generate cytotoxic T-lymphocytes (CTLs) toward human leukocyte antigen (HLA)-A24(+) cervical cancer. Two HPV16-E6 peptides at positions 75-83 and 91-100 effectively induced peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A24(+) cervical cancer patients. These HPV16-E6 peptide-induced CTLs showed cytotoxicity against HLA-A24+ and HPV16-E6 protein-expressing cervical cancer cells. Experiments with blocking antibodies and cold inhibition targets revealed that the cytotoxicity was mainly dependent on peptide-specific and CD8(+) T cells. In addition, based on our observation that induction of immunoglobulin G (IgG) reactive to administered CTL-directed peptides is correlated with clinical responses, we attempted to detect IgG reactive to HPV16-E6 peptides in the plasma of cancer patients. As a result, IgGs reactive to the HPV16-E6(91-100). peptide were detected in 4 of 12 cervical cancer patients. These results indicate that these HPV16-E6-derived peptides are good candidates in peptide-based immunotherapy for HLA-A24(+) cervical cancer patients.