Identification of human papillomavirus type 53 L1, E6 and E7 variants in isolates from Brazilian women

Human papillomavirus type 53 (HPV 53), which belongs to genus Alpha, species A6, has spread among women worldwide. Although it is classified as a probably high risk type, the association between HPV 53 and the development of neoplastic cervical disease is unclear, and HPV 53 is known to be genomically diverse. We investigated 15 cases of HPV 53 genital infection in women living in the state of Rio de Janeiro that were not associated with severe intraepithelial cervical neoplasia. To trace HPV 53 variants in this geographic area, we characterized the L1, E6 and E7 genes from these isolates, and undertook a phylogenetic analysis based on multiple alignment of their L1 sequences. After amplification and sequence analysis, we identified seven different L1-E6-E7 variants and a L1 co-infected isolate, which taken together had base pair changes at 29 different positions. The co-infected sample presented overlapped peaks at two positions. We also detected two new E6 genomic variants. Several base pair changes in the E6 region resulted in amino acid changes, three of which were non-conservative. The E7 gene was the most conserved sequence among those studied: in contrast, the E6 sequence reached a maximum difference of 2.79%. None of the HPV 53 isolates corresponded to the reference type. Dichotomical branching characteristic of HPV 53 was observed in all of the trees constructed, as well as in the concatenated phylogenetic tree. Probably, these variants pointing to evolutionary process, but they not appear to keep an increasing of pathogenesis Despite the limited number of samples analyzed in our work, we noticed that the same variant was found in more than one woman. Therefore, it is possible that such variants have been circulating in the female population in the state of Rio de Janeiro for a longer time or that due to host or genetic viral factors, these variants can spread more rapidly than others. (C) 2011 Elsevier B.V. All rights reserved.