Merkel cell polyomavirus DNA in CSF of paediatric patients with suspected meningitis or encephalitis

Background The clinical significance of Merkel cell polyomavirus (MCPyV) in pediatric central nervous system (CNS) infections remains uncertain, particularly in immunocompromised children. Objective To determine the frequency of MCPyV DNA in cerebrospinal fluid (CSF) from children with suspected viral meningitis or encephalitis and evaluate its association with HIV infection, CSF findings, and clinical outcomes. Methods CSF samples from 46 pediatric patients with suspected viral CNS infection were analyzed using TaqMan probe-based quantitative PCR targeting the large T-antigen gene. Positive specimens were confirmed by amplification of an independent VP1 target and bidirectional Sanger sequencing following conventional PCR re-amplification. Clinical, laboratory, and outcome data were compared using appropriate statistical tests. Results MCPyV DNA was detected in 6/46 patients (13.0%), all of whom were HIV-positive ( p = 0.001; sensitivity analysis excluding patients with unknown HIV status, p = 0.002). Four isolates belonged to genotype I and two to genotype IIc. Compared with MCPyV-negative patients, MCPyV-positive patients had higher CSF lymphocyte percentages (89% vs. 84%; p = 0.048), higher protein concentrations (79 vs. 68 mg/dL; p = 0.022), lower glucose concentrations (51 vs. 55 mg/dL; p = 0.038), and more frequent altered consciousness (83.3% vs. 37.5%; p = 0.039). EBV DNA co-detection was identified in one MCPyV-positive patient. Conclusions MCPyV DNA was detected exclusively in HIV-positive children and was associated with inflammatory CSF abnormalities. These findings suggest a possible association between MCPyV detection, immunosuppression, and CNS inflammation but do not establish causality. Larger multicenter studies are required.