Detection of HIV-1 DNA in microglia/macrophages,astrocytes and neurons isolated from brain tissue with HIV-1 encephalitis by laser capture microdissection

In HIV-1 encephalitis, HIV-1 replicates predominantly in macrophages and microglia. Astrocytes also carry HIV-1, but the infection of oligodendrocytes and neurons is debated. In this study we examined the presence of HIV-1 DNA in different brain cell types in 6 paraffin embedded, archival post-mortem pediatric and adult brain tissues with HIV-1 encephalitis by Laser Capture Microdissection (LCM). Sections from frontal cortex and basal ganglia were stained by immunohistochemistry for CD68 (microglia), GFAP (astrocytes), MAP2 (neurons), and p24 (HIV-1 positive cells) and different cell types were microdissected by LCM. Individual cells or pools of same type of cells were lysed, the cell lysates were subjected to PCR using HIV-1 gag SK38/SK39 primers, and presence of HIV-1 DNA was confirmed by Southern blotting. HIV-1 gag DNA was consistently detected by this procedure in the frontal cortex and basal ganglia in 1 to 20 p24 HIV-1 capsid positive cells, and in pools of 50 to 100 microglia/macrophage cells, 100 to 200 astrocytes, and 100 to 200 neurons in HIV-1 positive cases but not in HIV-1 negative controls. These findings suggest that in addition to microglia, the infection of astrocytes and neurons by HIV-1 may contribute to the development of HIV-1 disease in the brain.