Detection of Human Polyomavirus 6 DNA in the Cerebrospinal Fluid of HIV negative Patients with Neurological Diseases

Introduction: The family Polyomaviridae comprises thirteen human viruses that have been detected in various specimen types, mainly urine, skin and blood. Among all of them, only JC Polyomavirus (JCPyV) genome has been detected in Cerebrospinal Fluid (CSF). Recently, the unexpected finding of Human Polyomavirus 6 (HPyV6) DNA in the CSF from an HIV positive patient with leukoencephalopathy was reported. JCPyV being a recognized cause of Progressive Multifocal Leukoencephalopathy (PML) in immunodeficient subjects provides a precedent for polyomavirus causing neurological symptoms, but alternative explanations should be considered. The aims of the study was to explore the prevalence of the newly discovered HPyV6, Human Polyomavirus 7 (HPyV7) and Human Polyomavirus 9 (HPyV9), Merkel Cell Polyomavirus (MCPyV) in neurological diseases, in comparison with those of JCPyV. Material and methods:CSF have been collected from 51 HIV-positive patients affected with HIV-related leukoencephalopathies and 191 HIV-negative patients affected with other neurological diseases (OND), such as meningitis, encephalitis, and en-cephalomyelitis. DNA was isolated and real-time PCR assays for JCPyV, HPyV6, HPyV7, HPyV9 and MCPyV were conducted. RESULTS:JCPyV genome was detected in the CSF of 16/51 (31.4%) HIV-related leukoencephalopathies patients, HPyV6 genome in the CSF of 2/51 (3.9%) HIV-related leukoencephalopathies patients and in 37/191 (19.4%) HIV-negative patients with OND. MCPyV DNA was present in 9/191 (4.71%) CSF from HIV-negative OND patients, while HPyV7 and HPyV9 genomes were not amplified in any clinical specimens. Discussion and Conclusions: HPyV6 genome was found in a high percentage of the CSF of the OND patients, followed by MCPyV, whereas HPyV7 and HPyV9 genomes were not detected. HPyV6 has not been previously associated with any disease, and it is nonetheless possible that the HPyV6 sequences originated from the skin during CSF collection. Whether HPyV6 detection in CSF is associated with patients’s neurological disease, is indicative of contamination with skin microbiota, or reflects increased blood-brain permeability is unknown. Demonstrating a causative role will require further studies.