Human Papilloma Virus (HPV)

Categorization
Genome: DNA Virus, dsDNA Virus Structure: Nonenveloped Virus, Icosahedral Virus
Overview
  • Human Papilloma Viruses (HPV) are a family of related dsDNA viruses characterized by their capacity to promote tumorigenesis and their tropism for mucocutaneous tissues. A variety of different serotypes exist which differ in their tropism for different mucocutaneous geographies and oncogenic power.
Transmission
  • HPV is transmitted by close contact or fomites. Infections of genital epithelial tissues occurs via sexual transmission.
Pathogenesis
  • HPV can infect any type of squamous epithelium and establishes a chronic infection in the epithelial basal layer. As basal cells differentiate, HPV viruses replicate, assemble, and are ultimately shed with sloughed epithelial cells. The virus synthesizes two proteins, E6 and E7, which promote proliferation of epithelial cells, resulting in expansion of all the squamous epithelium's layers. In skin this manifests as acanthosis, parakeratosis, and hyperkeratosis. Certain serotypes of HPV, especially serotypes 16 and 18, are especially oncogenic and are associated with a variety of epithelial neoplasms, especially cervical cancer.
Clinical Consequences
  • Common Warts: Tend to occur on the hands
  • Plantar Warts: Occur on the sole of the feet
  • Anogenital Warts: Are sexually transmitted and are usually caused by subtypes 6 and 11
  • Cancers: A variety of cancers are associated with the highly oncogenic subtypes of HPV 16 and 18. Refer to interlinks but particularly note the association of HPV with cervical cancer
Prevention
  • Gardasil is a new vaccine against the subtypes of HPV which are most oncogenic (HPV 16 and 18) and those which tend to cause anogenital warts (HPV 6 and 11) is now available.