Papillomaviridae are small non-encapsulated viruses with a double-stranded DNA circular genome of approximately 8 kbp. Papillomavirus (PV) DNA has been recovered from the skin and lesions of many mammalian species. Moreover, PVs or their genetic material have also been found in birds and turtles. Many PVs seem to cause asymptomatic infections and have been recovered from the healthy skin of many mammals. Negative results in certain mammals could reflect inadequacies in experimental techniques or extinction/sorting events in certain host species. Other PVs induce conspicuous infections of the epithelia and give rise to hyperkeratotic lesions, such as plantar and hand warts in humans caused by HPV1, oral warts in dogs caused by CPV1 and horny warts in the cottontail rabbit caused by SfPV1. Infections by particular human PVs, such as HPV6 and HPV11, cause genital warts and are among the most common sexually transmitted infections.
Infectious agents can account for 20% of the global cancer burden. Several PVs are recognized by the World Health Organization as human carcinogens, as the link between cancer of the cervix and infection by so-called ‘high-risk’ human PVs (e.g. HPV16 or HPV18) is well established. World estimations in 2004 attribute more than 270,000 deaths to cervical cancer, 85% of them in developing countries (http://www.who.int/hpvcentre/en/). Globally, PVs account for more than 30% of all infection-associated cancers in humans, as they are also putatively involved in cancers of the penis, vagina, vulva, anus, perianal region and head and neck. The 2008 Nobel Prize in Physiology and Medicine awarded to Harald zur Hausen “for his discovery of human papilloma viruses causing cervical cancer” acknowledges the importance of this connection (http://nobelprize.org/nobel_prizes/medicine/laureates/2008/). Two vaccines using capsid proteins as immunogens from the most clinically relevant human PVs that cause cervical cancer have been recently licensed and seem to offer at least mid-lasting protection (4–6 years). Certain PV-related malignancies could thus become preventable diseases, but projections for 2030 still foresee more than 470,000 deaths and almost 4 million years of life lost due to cervical cancer in the absence of a widespread application of human PV vaccines (http://www.who.int/healthinfo/global_burden_disease/projections/en/index.html).
From: The clinical importance of understanding the evolution of papillomaviruses. Ignacio G. Bravo, Silvia de Sanjosé and Marc Gottschling. Trends in Microbiology. Volume 18, Issue 10, October 2010, Pages 432-438.
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