HUMAN-LEUKOCYTE ANTIGEN-A2.1 RESTRICTED CANDIDATE CYTOTOXIC T-LYMPHOCYTE EPITOPES OF HUMAN PAPILLOMAVIRUS TYPE-16 E6-PROTEIN AND E7-PROTEINIDENTIFIED BY USING THE PROCESSING-DEFECTIVE HUMAN CELL LINE-T2

Human papillomavirus type 16 (HPV-16) is strongly associated with cerv ical cancer. HPV-16 cytotoxic T lymphocyte (CTL) epitopes may be good candidates for the development of an antitumor peptide vaccine. A set of 240 overlapping peptides nine amino acids in length with an eight a mino acid overlap covering the entire sequence of the two viral oncoge nes E6 and E7 was synthesized and tested for its ability to bind to th e most common human leukocyte antigen class I molecule HLA-A2.1. Bindi ng was measured with the human processing defective cell line T2, whic h expresses high numbers of empty HLA-A2.1 molecules that are unstable at 37-degrees-C. These empty molecules can be stabilized by exogenous ly added peptides, and the extent of stabilization, measured by cell s urface HLA-A2.1-specific staining, can be taken as a measure of the re lative HLA-A2.1 binding affinity. Following this analysis, several HLA -A2.1 binding peptides were pinpointed. Preliminary data suggest that at least one of the high-affinity-binding peptides identified is immun ogenic even in an in vitro priming protocol, underlining the feasibili ty of the method described here to identify the immunogenic peptides a nd potential candidates for CTL peptide-based vaccines.