Human papillomavirus 39 (HPV39) is a high‑risk type of human papillomavirus belonging to the alpha‑7 species group. It infects mucosal epithelial cells and contributes to a small fraction of cervical, vulvar, vaginal and anal cancers. HPV39 is a circular double‑stranded DNA virus in the Papillomaviridae family.
Virology and Pathogenesis
HPV39 has an approximately 8 kb circular double‑stranded DNA genome encoding early proteins (E1, E2, E4, E5, E6 and E7) and late capsid proteins (L1 and L2). The virus enters basal keratinocytes through microabrasions and persists as an episome, with replication coordinated with epithelial differentiation. Persistent infection may lead to integration of viral DNA into the host chromosome, typically disrupting the E2 regulatory gene and leading to overexpression of the E6 and E7 oncoproteins. HPV39 E6 promotes degradation of p53, while E7 binds and inactivates the retinoblastoma protein, driving cells into the S phase and blocking apoptosis. These interactions disrupt cell cycle control and contribute to genomic instability and malignant transformation. HPV39 is less prevalent than HPV16 and HPV18 but shares similar oncogenic mechanisms. The virus evades host immunity by downregulating interferon signalling and antigen presentation. Factors such as smoking, a high number of sexual partners and immunosuppression increase the risk of persistence.
Clinical Associations and Prevention
HPV39 is detected in a minority of cervical cancers and high‑grade cervical intraepithelial neoplasia, including adenocarcinomas. It has also been reported in vulvar, vaginal, penile and anal cancers, though less frequently. HPV39 does not usually cause visible genital warts. Currently available HPV vaccines (bivalent, quadrivalent and nonavalent) do not include HPV39, so protection must rely on other measures. Cervical screening with Papanicolaou cytology and HPV DNA testing enables early detection of high‑risk infections and precancerous lesions. High‑grade lesions are managed with excisional or ablative procedures to prevent progression. Behavioural strategies such as condom use, limiting the number of sexual partners and smoking cessation reduce transmission and persistence but do not provide complete protection. Continued research may lead to broader vaccines covering types like HPV39. HPV39 is a high‑risk papillomavirus that contributes to a small fraction of cervical and other anogenital cancers. Although less common than other high‑risk types, its E6 and E7 proteins disrupt key tumour suppressors and drive oncogenesis. Without vaccine coverage, screening and safe sexual practices remain the primary means of controlling HPV39 infection. Related Terms: High‑risk HPV, HPV18, Cervical adenocarcinoma, HPV45, Screening