Abstract
Cervical cancer is the fourth most common malignant tumor in women worldwide and is closely related to human papillomavirus (HPV). Women have the highest susceptibility to HPV-52 type in Jingzhou, China. In this study, E6-E7 sequences of 183 HPV-52 positive samples were amplified by a polymerase chain reaction and sequenced. HPV-52 E6-E7 gene variations were analyzed. The phylogenetic tree was constructed using the Kimura 2-parameter method. The secondary structure of the protein was analyzed. The selective pressure to E6-E7 genes was estimated using PAML. In addition, the B cell epitopes of the E6-E7 sequences in HPV-52 were predicted by the ABCpred server. In E6 sequences, 15 single nucleotide variants were observed, including 6 nonsynonymous variants and 9 synonymous variants. In E7 sequences, 19 single nucleotide variants occurred, including 10 nonsynonymous variants and 9 synonymous variants. Sixamino acidvariants, including 3 nonconservative substitutions, were found in sequences encoding the alpha helix. Eight amino acid variants, including three nonconservative substitutions, occurred in sequences encoding the strand. Through phylogenetic analysis, the E6-E7 sequences were mainly distributed in B lineage. In HPV-52 E6-E7 sequences, no positively selected site was found. The nonconservative substitutions, such as K93R, K93E in E6, T37I, and D38N in E7, affected multiple hypothetical epitopes in the B cell. This study provides information for the investigation of HPV epidemic characters. The discovery of new variants of HPV-52 may lay the basis for the development of the virus diagnosis, further study of cervical cancer, and vaccine design in Central China.
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