Sequence Variations of Human Papillomavirus Type 16 E6 and E7 Genes in Cervical Cancer Isolates from Gabon

Abstract

Aims: HPV-16 variants distribution is reported to differ geographically and in their oncogenic potential for progression to cervical cancer. In this study, we investigated the HPV 16 variants distribution among women from Gabon. Methodology: Amplification of E6 and E7 genes of 29 HPV-16 isolates was performed by using type-specific primers PCR and then directly sequenced. The sequences obtained were aligned with the HPV-16 GenBank reference sequences. Results: Out of the 29 samples investigated, 25 were successfully amplified. In the 25 samples analyzed 9 and 3 nucleotide changes in E6 and E7 gene respectively were found. In the E6 gene, the most frequently observed mutation were C143G, G145T, T286A, A289G, C335T which led Q14D and H78Y non- synonymous amino acid variations. The others mutations found C109T; G132C; G132T; A403G were detected in 24% (6 of 25), 68% (17 of 25), 32% (8 of 25), 32% (8 of 25) respectively. The E7 gene appears to be better conserved than the E6 gene. Only 3 mutations were detected of which two were silent: T789C and T795G and the third A647G was missense mutation with substitution of Asparagine to Serine (N29S). This mutation was present in 32% (8 of 25) samples. All the variants detected in this study belonged to the Af1 (68%; 17 of 25) and Af2 (32%; 8 of 25) lineages Conclusion: This study reported for the first time the distribution of HPV-16 E6 and E7 genetic variants in cervical cancer cases in Gabon. Our results highlight the predominance of African lineage in Gabonese population.