HPV Definitions & Epidemiology
Human Papillomavirus (HPV) is a double-stranded DNA virus of the family Papovaviridae. It infects only epithelial cells in humans such as skin and mucus membranes. It can affect the lower genital tract including the vulva, vagina, urethra, penis, anal canal and perianal skin.
- Member of family Papovaviridae
- Double-strand DNA tumor viruses
- Circular genome of 7,800 base pairs
- Non-enveloped virion
- 45 – 55 nm. icosohedral capsid
- More than 100 sub-types of HPV
HPV Sub-types
The anogenital types of HPV can be divided into two groups:
Little or no oncogenic potential
(low risk)
- HPV 6, 11, 42, 43, 44
- Usually present as raised, acuminate, verrucous lesions but may also be flat non-pigmented papillomas
Significant oncogenic potential
(high risk)
- HPV 16, 18, 31, 33, 35, 51 and 52
- Almost always flat warts
Oncogenic viral types integrate the host cells’ DNA. This is accomplished by an alteration in the viral DNA at the site (E1 and E2 gene) that is responsible for regulation of the E6 and E7 viral genes. The loss of regulatory control produced by disturbed function of the viral E1 and E2 genes, allows excess production of HPV E6 and E7 proteins, which inactivate the host cells’ tumor suppressing efforts, allowing uncontrolled proliferation of the permanently mutated host cell.
Cofactors involved in HPV-induced oncogenesis
- Impaired immune response
- Epithelial cell type
- Co-carcinogens (i.e., cigarette use)
- Age of first intercourse