Expression of HIV regulatory and structural mRNA in the central nervous system

Objective: HIV encephalitis is observed in approximately one-half of AIDS autopsies. Although most investigators would agree that central nervous system (CNS) macrophages are the predominant infected cell in HIV encephalitis, there remains some controversy regarding whether other CNS cells can be infected by HIV and thus show the molecular characteristics of such an infection. Design and methods: Using reverse transcriptase polymerase chain reaction (PCR) and immunocytochemistry (ICC), we examined CNS tissues from AIDS and control autopsies for the presence of non-productive HIV infection. Results: Single-spliced mRNA for structural envelope proteins were detected in the basal ganglia of only one of nine HIV-seropositive autopsies without HIV encephalitis and none of five seronegative autopsy controls. Double-spliced mRNA for regulatory proteins (e.g., Nef and Tat) were not detected in either the seropositive non-HIV encephalitis or seronegative controls. Both single and double-spliced viral RNA could be detected in basal ganglia of 10 out of 13 autopsies with HIV encephalitis. Similar findings were obtained when cerebral white matter was examined. Using PCR primers that distinguish single from double-spliced mRNA, we found no evidence for selective expression of the Nef regulatory gene. Conclusions: These data suggest that expression of HIV mRNA in the CNS is limited to those patients with HIV encephalitis. Further HIV encephalitis appears to be a chronic permissive infection of the CNS, without evidence of restricted Nef transcript expression.