Immunosuppression increases JC polyomavirus large T antigen DNA load in the brains of patients without progressive multifocal leukoencephalopathy

The relationship between latent JC polyomavirus ( JCV) infection and progressive multifocal leukoencephalopathy (PML) remains unclear. In this study, JCV DNA was quantified by real-time polymerase chain reaction (qPCR) in brain and kidney tissue from patients without PML. Immunosuppressed patients had significantly higher JCV DNA levels in brain, compared with immunocompetent patients (P = .001). An inverse relationship was observed between CD4+ T-cell counts and qPCR-determined brain JCV load among patients with HIV infection (r² = -0.9; P = .01; n = 7). Higher kidney JCV DNA load was strongly associated with higher brain JCV DNA load (Spearman p = 0.65; P = .004; n = 18). These findings highlight the importance of latent JVC brain infection to the pathogenesis of PML.