Etiology of Progressive Multifocal Leukoencephalopathy: Identification of Papovavirus

Papovaviruses were identified in brains of 13 patients with progressive multifocal leukoencephalopathy, asubacute human demyelinating disease. Fluorescent-antibody staining and electron microscopical agglutination technics demonstrated the JC type of papovavirus in 11 patients. Simian-virus 40 and the virus of progressive multifocal leukoencephalopathy were isolated from the first two patients studied, but all subsequent isolates were of the JC-virus type, and the BK type was not implicated in the disease. The use of monospecific rabbit serums to identify viral antigens in the brain tissue of patients and to serotype by electron microscopy virions extracted directly from brain demonstrates that rapid diagnostic methods can be employed in this disease. (N Engl J Med 289:1278–1282, 1973) Although progressive multifocal leukoencephalopathy (PML) is a rare disease, the recovery of viruses from patients with this disorder has been of interest, since it is the first consistent association of viruses with a subacute or chronic human demyelinating disease.¹ Furthermore, these isolations have been the first evidence that viruses related to simian-virus 40 (SV40) can cause disease in man. The viruses recovered from patients with progressive multifocal leukoencephalopathy have proved oncogenic for hamsters, as indicated by Walker et al.² and by Narayan (unpublished data), and, in some cases, have transformed human cells in culture as found by Narayan (unpublished data).