Polyomaviruses: Progressive multifocal leukoencephalopathy and other diseases

Abstract

Polyomaviruses are small, nonenveloped, double-stranded DNA viruses, which are widely distributed in nature. Viruses of this family infect many species including humans, monkeys, cattle, rabbits, rodents, and birds. The viruses are species specific and they do not naturally infect any species other than their natural hosts. Primary infections with human polyomaviruses generally occur in childhood and are not associated with serious illness, but the viruses persist in the infected host. Most of the diseases associated with human polyomaviruses occur later in life in immunosuppressed groups, probably as a result of recrudescence of active infection brought about by the immune deficiency of the host. Human illnesses associated with these viruses include progressive multifocal leukoencephalopathy (PML) which is caused by JC polyomavirus (JCPyV) and is a frequent complication in individuals with HIV/AIDS, nephropathy in renal transplant recipients, and hemorrhagic cystitis in bone marrow transplant recipients, both caused by BK polyomavirus (BKPyV) and Merkel cell carcinoma, which is associated with the recently recognized Merkel cell polyomavirus (MCPyV).