Epitome mapping of E6 and E7 proteins from high-risk oncogenic HPV types 16, 18 and 45

Abstract Background It is crucial to reveal entire epitomes of more target homologous proteins and specificity of each mapped B cell epitope (BCE) within them for the development of high-risk (hr-) human papillomavirus (HPV) type-specific diagnostic reagents. Methods Recombinant E6 and -E7 oncoproteins from HPV16/18/45 were immunized mice to prepare Rabbit antisera. Overlapping 16mer/8mer-peptides for two rounds of antigenic peptide and fine BCE motif mapping were expressed as GST188 fusion proteins. Fine BCEs were delineated by Western blot and sequence alignment. Results In this work, we decoded six epitomes of E6 and E7 oncoproteins from three HPV types 16, 18 and 45 that are the most common hr-HPVs in cervical cancer patients worldwide, in which total 35 fine BCEs (8, 6 and 4 for E6; 7, 6 and 4 for E7) were mapped using rabbit antisera to respective recombinant proteins. The specificity of each mapped BCE among 20 defined or possible hr-HPVs was delineated by sequence alignment based on BCE minimal motif. According to similarities of immune responses to E6/E7 existed among rabbit and humans, 7 human-recognizing (HR) BCE motifs in HR-peptides of HPV16/18-E6 and E7 proteins were delimitated by comparing with corresponding rabbit-recognizing BCEs. Also, the unique BCE distribution within three delineated E7 epitomes was confirmed, in which almost mapped BCEs were clustered at the first half of the molecules, suggesting that it may be a common characteristic of hr-HPV E7 proteins. Conclusions The results would form the basis for identifying HR-BCEs and developing serodiagnostic reagents used in HPV-based cervical cancer screening and HPV-positive women managing.