Papillomavirus

Papillomavirus refers to viruses in the family Papillomaviridae, a large group of non-enveloped, icosahedral viruses with circular double-stranded DNA genomes. They infect keratinocytes of stratified squamous epithelia, including skin and mucosal surfaces, and establish site-specific infections that are often chronic.

The viral life cycle is tied to epithelial differentiation. L1 and L2 encode structural proteins; expression of late genes occurs in the superficial layers, while early genes such as E6 and E7 modulate the host cell cycle. Some high-risk types express oncoproteins that can disrupt p53 and Rb pathways, contributing to cellular changes associated with neoplasia.

Transmission typically occurs by direct contact; skin-to-skin, sexual contact, or fomites. Infections range from benign warts on hands or feet to mucosal lesions such as genital or oral warts. Certain human papillomavirus (HPV) types are associated with cancer, while others remain low risk.

Taxonomy centers on the Papillomaviridae family. Genera include Alphapapillomavirus (which includes most mucosal, high-risk HPV types), Betapapillomavirus, and others. The viruses have tropism for epithelial tissues and can be cutaneous or mucosal.

Diagnosis is usually clinical for external warts; HPV DNA testing is used in cervical cancer screening alongside cytology (Pap tests). There is no antiviral cure for established infection; treatment focuses on removing or reducing lesions and monitoring precancerous changes.

Prevention relies on vaccines based on virus-like particles composed of the L1 protein. Prophylactic HPV vaccines (bivalent, quadrivalent, nonavalent) protect against multiple HPV types and reduce infection, genital warts, and cancer risk. Vaccination is recommended for preadolescents and certain older age groups.

Animal papillomaviruses cause disease in various species and are used in comparative studies of viral oncogenesis.