Human polyomavirus 7 (HPyV7) is a non‑enveloped double‑stranded DNA virus in the Polyomaviridae family. It was identified in 2010 through rolling circle amplification of skin samples and is a common component of the cutaneous flora of healthy adults.
Explanation
HPyV7 was discovered concurrently with HPyV6 using rolling circle amplification, which selectively amplifies circular DNA genomes. The virus was found in normal skin swabs and hair samples along with Merkel cell polyomavirus and HPyV6. Comparative genomic analyses show that HPyV7 shares roughly 68 % sequence identity with HPyV6 and both viruses are classified in the genus Deltapolyomavirus. The ~5 kilobase genome of HPyV7 encodes small and large T antigens and the capsid proteins VP1, VP2, and VP3, reflecting a typical polyomavirus organization. Serologic studies indicate that HPyV7 infection is widespread but somewhat less prevalent than HPyV6; antibody prevalence ranges from about 35 % to 85 % and increases with age. Detection of HPyV7 DNA in cutaneous samples is lower, with reported prevalence from around 2 % to 14 % and occasional persistent shedding. As with other cutaneous polyomaviruses, HPyV7 is thought to be acquired in early childhood and to remain latent or persistent in the skin. The clinical importance of HPyV7 remains unclear. Surveys of tumour tissues have failed to show significant viral loads, suggesting that HPyV7 is unlikely to contribute to oncogenesis. A few case reports have identified pruritic, velvet-textured plaques in lung transplant recipients receiving immunosuppressive therapy, where high viral loads of HPyV7 were detected in affected skin. Histologically, viral particles were observed in keratinocytes, pointing to an active local infection. However, such reports are rare and causal associations are not established, leaving HPyV7 primarily considered a commensal virus.
Noteworthy Findings
Serologic surveys show that HPyV7 antibodies are present in roughly 35–85 % of adults, with the lowest prevalence observed in young children and a steady rise through adolescence and adulthood. DNA-based studies report skin prevalence of 2–14 %, with a minority of individuals shedding virus over time. The virus has not been detected at meaningful levels in blood or urine, underscoring its skin tropism. Rare case reports describe intensely itchy, velvet-like plaques in immunosuppressed transplant recipients, where biopsy specimens revealed HPyV7 replication in keratinocytes. Phylogenetically, HPyV7 clusters with other Deltapolyomaviruses, including HPyV6, MW polyomavirus and STL polyomavirus, supporting a shared evolutionary history. Human polyomavirus 7 is a common inhabitant of the human skin and appears to persist without causing disease in most individuals. While occasional case reports suggest a link to pruritic dermatoses under conditions of immunosuppression, current evidence points to HPyV7 as a benign part of the cutaneous virome. Related Terms: Human Polyomavirus 6, MW Polyomavirus, STL Polyomavirus, New Jersey Polyomavirus, Merkel Cell Polyomavirus