John Cunningham virus

Last revised by Assoc Prof Craig Hacking on 18 Aug 2021

John Cunningham virus (or human polyomavirus 2), universally known as the JC virus, is a ubiquitous double-stranded DNA virus of the polyomaviridae family 1. In immunocompromised individuals, reactivation can lead to a variety of disease of the central nervous system, the most common of which is progressive multifocal leukoencephalopathy (PML).

It has been reported that ~70% of adults have been exposed to this virus; however, no significant clinical syndrome has been associated with this acquisition in the majority of immunocompetent hosts 1

Numerous causes of immunosuppression have been implicated in reactivation of the virus, including HIV/AIDS, malignancy (e.g. lymphoma), immonusuppressants, and immunomodulators (e.g. natalizumab for multiple sclerosis). 

Infection with JC virus, usually asymptomatic, results in latent infection in various organs and tissues of the body. When patients are immunocompromised, the virus can reactivate and migrate to the central nervous system, with a predilection for glial cells, thus resulting in the classical leukoencephalopathy of progressive multifocal leukoencephalopathy (PML) 6.

Occasionally, mutations of the virus result in other cell types being targeted, with resultant distinct clinical manifestations, including 4-6

The virus was first described by Åström et al. in 1958 2, and was first isolated in 1971 by Padgett et al. The latter group assigned the name of the patient to the virus 3.

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