Novel HPV-6 variants of human papillomavirus causing recurrent respiratory papillomatosis in southern Africa.

There is currently no information regarding the genetic diversity of HPV-6 variants circulating in South Africa. The aim of this study was to determine the HPV-6 variants affecting patients with recurrent respiratory papillomatosis, to determine whether mutations correlate with disease severity and identify molecular determinants of virulence with prognostic relevance. HPV-6 variants were identified based on genome changes within the 712-991 bp region encompassing the non-coding region (URR) of the genome, with variations in length resulting from insertions and duplications, and the 453-bp gene encoding the E6 protein. Based on manual comparison of sequence data from the URR, the isolates were identified as HPV-6a and HPV-6vc variants. Three novel HPV-6 variants were identified: one based on a mutation in the E6 region; two based on changes in the URR including a unique substitution detected in three isolates and an insertion and 170-bp duplication in the URR genome in one patient, who had clinical features of severe disease.