HUMAN CTL EPITOPES ENCODED BY HUMAN PAPILLOMAVIRUS TYPE-16 E6 AND E7 IDENTIFIED THROUGH IN-VIVO AND IN-VITRO IMMUNOGENICITY STUDIES OF HLA-A-ASTERISK-0201-BINDING PEPTIDES

Human papillomavirus type 16 (HPV16) is strongly associated with cervi cal carcinogenesis, The HPV16 E6 and E7 oncoproteins are constitutivel y expressed in the majority of cervical tumor cells and are, therefore , attractive targets for CTL-mediated immunotherapy. In mice, the outg rowth of a lethal dose of HPV16-induced tumor cells has been prevented by vaccination with a CTL epitope encoded by HPV16 E7, indicating. th e feasibility of peptide immunization to obtain antitumor CTL response s. In the present study, the immunogenicity of 9 HLA-A0201-binding pe ptides encoded by HPV16 E6 and E7 was analyzed in vivo in HLA-A0201K( b) transgenic mice and in vitro in CTL cultures induced from PBMC of H LA-A0201(+) healthy donors. Four peptides with a good binding affinit y were immunogenic in HLA-A0201K(b) transgenic mice, and three of the m were also highly immunogenic in CTL induction experiments with PBMC of HLA-A0201(+) healthy donors. Human CTL clones specific for these t hree peptides were capable of lysing the HPV16 E7-containing HLA-A020 1(-) cervical carcinoma cell line CaSki. These E7-derived peptides (11 -20, YMLDLQPETT; 82-90, LLMGTLGIV; 86-93, TLGIVCPI), therefore, are li kely to represent naturally processed human CTL epitopes of HPV16. Add itionally, these three HPV16-encoded peptides have the highest affinit y of binding to the HLA-A0201 molecule. In this study, peptides with a lower binding affinity were less immunogenic. Therefore, our data il lustrate that the HLA-binding affinity of a peptide has a major impact on its immunogenicity, In conclusion, we have identified immunogenic peptides encoded by HPV16 E6 and E7 that could be used in vaccines for the prevention and treatment oi cervical carcinoma.