Papilloma viruses are small, nonenveloped, circular, double-stranded DNA viruses. These viruses are abundant in nature and cause infections in humans, dogs, cattle, monkeys, and many other species. The Papillomaviridae family (Table 1) includes the human papillomaviruses (HPVs). HPVs cause human warts. They exhibit a tissue tropism for either cutaneous or mucosal tissue. The viruses have not been cultivated in cell culture, which prevents the production of type-specific antigens and corresponding typing antisera. HPVs are divided into more than 200 genotypes based on the viral DNA sequences; approximately 80 of those have been well characterized. Much attention has been focused on the more than 30 sexually transmitted genotypes and their role in the pathogenesis of cancer. The various HPV genotypes have differing cellular tropisms, resulting in defined variation in the clinical presentation of the warts. For example, HPV-1 is associated with plantar warts; HPV-2 and HPV-4 are associated with common warts of the hands; and HPV-6, HPV-11, and others are associated with genital warts. Fifteen to 20 types of HPV cause virtu ally all cases of cervical cancer, with types 16 and 18 causing more than 60% of cases. Type 16 is also responsible for a subset of cancers of the oropharynx and penile cancer in men (Table 1).
Table1. Papillomaviruses
HPV infection is the most prevalent sexually transmit ted viral disease in the United States; it is estimated that more than 65 million Americans are living with an incur able STD, such as HPV or HSV infection. Infection is detected using histopathologic or cytologic examination of cutaneous biopsy or cells, respectively, and DNA probe assays for identification of specific genotypes in infected epithelial cells. A single, liquid-based cytology sample can be used for cytology and genotyping. Several commercial HPV assays currently are available in the United States, including HC2 (Qiagen), Cervista HPR HR (Hologic), Roche Amplicor HPV Test (Roche Molecular Diagnos tics), GenProbe Aptima HPV Test (GenProbe), Abbott RealTime High Risk HPV Test (Abbott Molecular), PreTect HPV-Proofer (Norchip) and NucliSENS Easy Q HPV v1 Test (bioMeriéux). Two vaccines for HPV are currently licensed by the FDA: Cervarix (Glaxo Smith Kline, United Kingdom and Gardasil (Merck & Co., Inc, Whitehouse Station, N.J.). The vaccines are a derivative of the protein viral coat and provide some protective immunity to HPV16.
