The fine structure of acquired immunodeficiency syndrome encephalopathy.

Involvement of the central nervous system with the human immunodeficiency virus is thought to underlie the clinical and pathologic features of acquired immunodeficiency syndrome (AIDS) encephalopathy. Although morphologic, immunocytochemical, and molecular data point to predominant human immunodeficiency virus infection of multinucleated and mononuclear macrophages, neuroglial and other cells are thought to be involved as well. Electron microscopic studies of biopsy tissue that might further define the neuropathologic changes have been limited. The opportunity to study well-preserved biopsy tissue from a 38-year-old man with the acute onset of dementia and AIDS encephalopathy prompted this report. Human immunodeficiency virus was seen budding from the surface of multinucleated and mononuclear cells with morphologic features of macrophages; a rare astrocyte process showed evidence of viral infection as well. Macrophages were noted within the walls of blood vessels and in intimate contact with lymphocytes within the neuropil. Notably rare were tubuloreticular inclusions, interferon-related cytoplasmic structures commonly found in systemic endothelial cells and lymphocytes in AIDS. Their relative scarcity may signify reduced interferon production in AIDS encephalopathy.