Characterization of a new genotype of Betapapillomavirus HPV 17 through L1, E7, E7 and LCR sequences

Background. Human papillomavirus (HPV) exhibits epithelial and mucosal tropism. HPV type 17 belongs to the Betapapillomavirus genus and molecular cloning experiments have identified two subtypes (17a and 17b) isolated from epidermodysplasia verruciformis (EV). HPV subtypes are characterized by dissimilarities from 2 to 10% at the nucleotide level from their referenced HPV. The aim of this study was to characterize the L1, E6, E7 and LCR sequences from an isolate from the oral mucosa of an asymptomatic woman.

Methods. The whole late gene 1 (L1) was amplified using several sets of primers. The complete early genes 6 and 7 (E6, E7) and the long control region (LCR) were amplified using specific primers. Potential binding sites for transcriptional factors within the LCR were also investigated.

Results. Within these sets, the DNA sequence was altered at 91 positions (68 in L1, 13 in E6, 8 in E7, and 2 in LCR sequences). L1 analysis showed high dissimilarity compared with the HPV 17 prototype, reaching 4% of nucleotide substitutions and leading to a probability third 17 subtype. The E6 oncoprotein presented the highest modification among the sequences !2 studied, with four amino acid changes in comparison with the prototype isolate. The amino acid was modified at a position 62 (S-T), a zinc-binding domain (CxxC(C)29 CxxC).

Discussion. Our findings provide data on genetic variations seen in this genotype, reaching to dichotomic branching and pointing to an evolutionary process. The oral cavity has a large HPV spectrum and may be implicated in the evolution of this virus, allowing it to adapt to sites other than its original niche, may drive to produce adaptive variants of this genotype