Human papillomavirus (HPV) is a double-stranded DNA virus containing only eight genes. It infects epithelial cells and is usually transmitted by sexual contact.
There are more than 100 subtypes of HPV:
- low risk – HPV 6 and 11, which can cause anogenital warts and respiratory papillomatosis
- high risk – HPV 16 and 18, which can cause cervical, anogenital and head and neck cancers. Other high risks are 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 68. HPV 16, 18 are responsible for 70% of cervical cancers. Currently, the DNA amplication tests used in the NHS only differentiate between 'high-risk' and 'low-risk' HPVs varieties.
HPV infection is endemic within the population.
HPV proteins E6, E7 interact with cell proteins p53, pRb.
In total, 99% of cervical cancers are estimated to be owing to HPV. Note that most women build up an immunity to the virus. If this was not the case, exposure to HPV would lead to cervical carcinoma in all women.