Research Article

E6 and E7 gene sequences of human papillomavirus type 13 isolated from a young native girl from the Brazilian Amazon


Human papillomavirus (HPV) type 13 is associated with focal epithelial hyperplasia, a benign and self-limited disease of oral mucosa. It is a rare finding, most often seen among young American natives. We carried out a molecular characterization case study of HPV type 13 isolated from a 14-year-old native girl living in Amazonia, in the northern region of Brazil, by describing the E6 and E7 open reading frame (ORF) sequences and comparing them to the only reference sequence in GenBank, which came from a Turkish isolate. The E6 and E7 ORFs were amplified by PCR, and the amplicons were purified and cloned in E. coli using the pCR®-4 TOPO® vector. The purified recombinant plasmids were automatically sequenced, showing 98 and 94% similarity to the E6 and E7 ORFs from the reference sequence, respectively. Six mutations were identified in the E6 ORF, but these changed only three amino acids in the final protein. In the E7 ORF, we found three transversions and one deletion of nine base pairs, which led to three amino acid mutations and three amino acid deletions in the final protein. The mutations in E6 ORF gave no predicted changes in the final protein, while the mutations in E7 were predicted to cause changes in the protein. We conclude that the E6 and E7 ORFs in HPV-13 from the Amazonia and Turkey isolates have a high degree of genetic similarity.