POLYOMAVIRUSES AND CENTRAL-NERVOUS-SYSTEM DISEASE

There are two human polyomaviruses, JC virus (JCV) and BK virus (BKV). Most of the population is infected with these viruses at an early age and the viruses can persist indefinitely without known adverse effect s in immunocompetent individuals. There are conflicting reports whethe r these two viruses are latent in the central nervous system or are re stricted initially to the renal system. Both JCV and BKV, together wit h the simian polyomavirus simian virus 40 (SV40), have been associated with central nervous system disease. In particular, JCV is associated with the demyelinating disease progressive multifocal leukoencephalop athy (PML) which was once considered only a rare complication of immun osuppression in transplant recipients. With the advent of the AIDS pan demic, PML has become of increasing importance and is now considered r esponsible for the death of 4% of HIV-infected individuals. Both BKV a nd SV40 have been detected in the human central nervous system, but th ere is still controversy on what correlation, if any, these two viruse s have with disease. Current research has focused on the epidemiology and pathogenesis of polyomavirus infections to try to understand the r e-activation process in immunosuppressed individuals. This will lead t o improvements in the differential diagnosis and treatment of PML. Fur ther analysis of other neurological complications, to see what role po lyomavirus plays in these infections, are required. (C) 1998 Chapman & Hall.