Association of human polyomavirus JC with peripheral blood of immunoimpaired and healthy individuals.

JC virus (JCV) infection is regularly asymptomatic in healthy individuals. In contrast, in immunocompromised individuals, highly activated virus replication may lead to PML. Peripheral blood cells (PBCs) are found to harbor JCV DNA in healthy and diseased individuals and it is discussed that they might be responsible for dissemination of the virus to the central nervous system (CNS) during persistence. To better understand the role of JCV DNA in PBCs for persistent infection and pathogenesis, the authors characterized the extent of JCV infection in Ficoll-gradient purified blood cells (peripheral blood mononuclear cells [PBMCs]) of healthy and human immunodeficiency virus type 1 (HIV-1)-infected individuals. Virus activation in PBMCs from healthy JCV-infected individuals was found at a rate of 0% to 38% at low polymerase chain reaction (PCR) sensitivity. In progressive multifocal leukoencephalopathy (PML) patients, a stronger signal was found, indicating increased virus activation. JCV DNA was regularly detected in T and B lymphocytes and in monocytes at low levels. However, granulocytes were shown to be the predominant reservoir of JCV DNA harboring high copy numbers. Although the overall distribution of viral genomes holds true for the population studied, in the individual, a markedly changed pattern of distribution can be found.