Identification of B cell epitopes reactive to human papillomavirus type-16L1- derived peptides

BACKGROUND: Persistent infection of human papillomavirus (HPV) types 16 and 18 causes cervical cancer. To better understand immune responses to the prophylactic vaccine, HPV 16/18 L1 virus-like particles (HPV-VLPs), we investigated B cell epitopes of HPV16 L1-derived peptides. METHODS: Sera from mice immunized with HPV-16/18 L1 VLPs were analyzed for their IgG titers against 10 different HPV16 L1-derived peptides (20-mer) that contain human leukocyte antigen (HLA)-class I A-2, A-24 and class II DR. RESULTS: One 20-mer peptide at positions 300 to 319 was identified as a common B cell epitope in both Balb/c (H-2d) and C57BL/6 (H-2b) mice. Mapping analysis showed that the 10-amino-acid sequence at positions 304 to 313 was an immunogenic portion. It is of note that the binding capability of this 10-mer peptide to the HLA-A2 and HLA-A24 molecules was confirmed by the HLA class I stabilization assay. In addition, one unique 20-mer was determined as a B cell epitope in each strain. CONCLUSIONS: These results might provide new information for better understanding of immune responses to HPV 16 L1.