WU and KI polyomaviruses remain orphans in adults.

To the Editor—We read with interest the brief report by Barzon et al [1] showing that WU and KI polyomaviruses (WUPyV and KIPyV) reactivate and are frequently detectable in the brains of human immunodeficiency virus (HIV)–positive patients without being associated with progressive multifocal leukoencephalopathy. We also recently disproved such an association between novel polyomaviruses (including lymphotropic polyomavirus [LPyV] and Merkel cell carcinoma polyomavirus [MCPyV]) and progressive multifocal leukoencephalopathy in HIV-negative patients [2]. However, because the prevalence of novel polyomaviruses remains high and because they have been shown to reactivate under conditions of immune deficiency [3], they could still prove to be useful as surrogate markers of functional immunodeficiency, as was recently proposed for another orphan virus, torquetenovirus (TTV) [4]. Therefore, we analyzed the occurrence of WUPyV, KIPyV, LPyV, and MCPyV viremia (by the same methods used previously [3]) at the time of peak TTV viremia after high-dose chemotherapy supported by autologous stem cell transplant in 17 patients with multiple myeloma, 1 with non-Hodgkin lymphoma, and 1 with systemic sclerosis. All samples tested negative. It remains difficult to identify the body site with the highest prevalence and, hence, the greatest sensitivity for these viruses; it could be feces [5], in contrast to urine for JC and BK polyomaviruses [6]. Given that many polyomaviruses are lymphotropic and retain oncogenic potential, we investigated their occurrence in lymph node biopsy samples from patients with lymphoma or leukemia. We could not find any occurrence of WUPyV, KIPyV, LPyV, and MCPyV in any of 49 lymph node samples tested (from, namely, 11 patients with follicular lymphoma, 14 with diffuse large B cell lymphoma, 10 with B cell chronic lymphocytic leukemia, 7 with Hodgkin lymphoma, 2 with hairy cell leukemia, 2 with mantle cell lymphoma, 1 with Burkitt lymphoma, 1 with splenic marginal zone lymphoma, and 1 with B cell acute lymphoblastic leukemia).