Seroepidemiology of human polyomaviruses.

In addition to the previously characterized viruses BK and JC, three new human polyomaviruses (Pys) have been recently identified: KIV, WUV, and Merkel Cell Py (MCV). Using an ELISA employing recombinant VP1 capsid proteins, we have determined the seroprevalence of KIV, WUV, and MCV, along with BKV and JCV, and the monkey viruses SV40 and LPV. Soluble VP1 proteins were used to assess crossreactivity between viruses. We found the seroprevalence (+/- 1%) in healthy adult blood donors (1501) was SV40 (9%), BKV (82%), JCV (39%), LPV (15%), KIV (55%), WUV (69%), MCV strain 350 (25%), and MCV strain 339 (42%). Competition assays detected no sero-crossreactivity between the VP1 proteins of LPV or MCV or between WUV and KIV. There was considerable sero-crossreactivity between SV40 and BKV, and to a lesser extent, between SV40 and JCV VP1 proteins. After correcting for crossreactivity, the SV40 seroprevalence was approximately 2%. The seroprevalence in children under 21 years of age (n = 721) for all Pys was similar to that of the adult population, suggesting that primary exposure to these viruses likely occurs in childhood.

KI, WU and Merkel cell polyomaviruses: a new era for human polyomavirus research.

The recent discoveries of KI, WU, and Merkel cell polyomaviruses (PyVs) have rekindled interest in the Polyomaviridae and their relation to human disease. Although it may be too early to draw firm conclusions, it seems apparent that these new viruses follow precedents established by other Py viruses: a benign initial infection at an early age, widespread prevalence in the population, and pathologic consequences only in the elderly and/or immunosuppressed. The discovery of Merkel cell PyV (MCPyV) integration into the malignant cell genome immediately implicates this agent in an oncogenic process predicted by previous research with SV40 and murine PyV (MPyV). Their discovery is another reminder that we certainly have not seen the end of novel human polyomavirus identification, but rather the beginning of a new era.