Beta-papillomavirus DNA loads in hair follicles of immunocompetent people and organ transplant recipients

There is increasing evidence of an association between human papillomaviruses (HPV) of the beta-genus (beta-PV) and the development of cutaneous squamous cell carcinoma (SCC). The viral DNA load may be an important determinant of pathogenicity, but there are currently no baseline epidemiological data relating to load in people without SCC. We investigated DNA-loads of eight beta-PV types previously associated with risk of SCC. We collected eyebrow hairs from immunocompetent people (ICP) and organ transplant recipients (OTR), determined load by quantitative PCR and obtained demographic, phenotypic, and sun exposure information. Viral loads for ICP from Australia (n = 241) and Italy (n = 223) and OTR from across Europe (n = 318) spanned seven orders of magnitude. The median loads for all types were below one viral DNA copy per 60 cells and were highest for HPV5, HPV8 and HPV20. None of the populations had consistently higher viral loads for all 8 types. However, a higher proportion of OTR were in the top deciles of viral load distributions for six of the eight beta-PV types examined. In a nested analysis of Italian OTR and ICP, this finding was significant for six beta-PV types and cumulative load. Increasing age was significantly associated with higher viral loads in Australia, and there was a weak trend for higher loads with the time elapsed since transplantation in the OTR. We observed a wide distribution of beta-PV loads with OTR significantly more likely to have the highest viral loads. Thus, viral loads may be an important contributor to the higher risk of SCC in OTR.