Virologic and serologic studies of progressive multifocal leukoencephalopathy.

The human polyomavirus JCV has been associated with diseased brain tissue from 54 cases of PML. The disease occurred in persons of all ages--the youngest being 5 years old--whose immune mechanisms were depressed for any of a variety of reasons. In six patients the disease ceased progressing and they stabilized or improved. The brains of two of these, who died months or years later, were found to be free of active PML at autopsy. Sera from 21 patients had HAI antibodies against JCV, but none had antibodies against T or the common internal antigens, and only one had IgM antibodies detectable by immunofluorescent staining. Nine CSF were devoid of JCV-related antibodies except for one which gave an HAI titer of 8. Virus has been isolated from 15 PML brains, and preliminary studies indicate that one isolate, while clearly of JCV type, is serologically distinguishable from prototype Mad 1 JCV.