Human papillomavirus 31 (HPV31) is a high‑risk type of human papillomavirus belonging to the alpha‑9 species group. It infects mucosal epithelium and is implicated in a subset of cervical, anal and other anogenital cancers. HPV31 is a circular double‑stranded DNA virus in the Papillomaviridae family.
Virology and Pathogenic Features
HPV31 has an approximately 8 kb circular double‑stranded DNA genome encoding early proteins (E1, E2, E4, E5, E6 and E7) and late structural proteins (L1 and L2). Infection occurs through microabrasions that allow the virus to enter basal keratinocytes. The viral genome persists as an episome and replicates in synchrony with epithelial differentiation. In persistent infections the viral genome may integrate into host chromosomes, disrupting the E2 regulatory gene and driving increased expression of the E6 and E7 oncoproteins. HPV31 E6 promotes degradation of p53, while E7 binds and inactivates the retinoblastoma protein, leading to uncontrolled cell cycle progression and inhibition of apoptosis. Although less common than HPV16 or HPV18, HPV31 has significant oncogenic potential and is frequently detected in high‑grade cervical intraepithelial neoplasia. The virus can downregulate interferon signalling and antigen presentation to evade host immunity. Clearance is mediated by cell‑mediated immune responses but is less likely in the presence of co‑factors such as smoking, long‑term hormonal contraception, multiple sexual partners and immunosuppression.
Clinical Significance and Prevention
HPV31, together with types 33, 45, 52 and 58, contributes to approximately 15 % of cervical cancers and high‑grade precursor lesions. It is associated with squamous and glandular lesions of the cervix and has been detected in anal, vulvar, vaginal and penile cancers. High‑grade cervical intraepithelial neoplasia caused by HPV31 can progress to invasive carcinoma if untreated. The nonavalent HPV vaccine includes HPV31 and generates neutralising antibodies against its L1 capsid protein, providing prophylactic protection. HPV DNA testing and cytology allow detection of HPV31 infection and associated lesions during screening. Management of high‑grade lesions involves excisional or ablative therapy. Because transmission occurs mainly through sexual contact, risk can be reduced by condom use, limiting numbers of partners and smoking cessation, but these measures do not eliminate infection risk. HPV31 is a high‑risk papillomavirus that contributes to a notable fraction of cervical and other anogenital cancers. Its E6 and E7 oncoproteins disrupt critical tumour suppressor pathways, and its inclusion in the nonavalent vaccine underlines its public health importance. Vaccination, regular screening and safe sexual practices help mitigate the impact of HPV31 infection. Related Terms: Oncogenic HPV, Nonavalent HPV vaccine, High‑grade cervical intraepithelial neoplasia, HPV33, HPV16