HPVs are non-enveloped, double-stranded DNA viruses, which are tropic for mucosal tissues. The genome consists of three functionally divided regions: (a) a noncoding regulatory region; (b) an early proteins region, which encodes for six early proteins (E1, E2, E4-E7); and (c) a late region, which encodes for the viral capsid proteins L1 and L2. HPVs infect basal epithelial (skin or mucosal) cells. More than 200 HPV genotypes have been identified. Oncogenic genotypes include HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 66.
