Ultrastructural studies in the lytic phase of progressive multifocal leukoencephalopathy in AIDS patients

Brain fragments from eight cases (four autopsies and four biopsies) of patients with acquired immune deficiency syndrome (AIDS) with JC virus (JCV) lytic infections were examined ultrastructurally. Particular efforts were made to look for virions and their subcellular distribution in cells not usually involved by papovavirus infection. The cellular and subcellular distribution of virions was investigated with emphasis on cell types not normally associated with papovavirus infection. The pattern of JCV infection was as follows: 1) oligodendrocytes; nucleus only, 7 cases; cytoplasm only, no cases; 2) astrocytes (normal and bizarre; nucleus and cytoplasm, two cases; cytoplasm only, four cases; 3) macrophages; nucleus and cytoplasm, one case; cytoplasm only, four cases; and 4) neurons; nucleus and cytoplasm, two cases; cytoplasm only, three cases. Perivascular, endothelial, ependymal, and microglial cells were never infected. Our ultrastructural data indicate that cell types other than oligodendrocytes can be involved productively by JCV in the lytic phase of progressive multifocal leukoencephalopathy (PML) in AIDS patients. Neuronal cells, especially, can be infected productively by the JCV, and this should be considered in clinical interpretation of cortical symptoms and signs in suspected or proven cases of PML.