TEMPORAL PATTERNS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 TRANSCRIPTS IN HUMAN FETAL ASTROCYTES

Human immunodeficiency virus type 1 (HIV-1) infection of the developin g central nervous system results in a dementing process in children, t ermed HIV-1-associated encephalopathy. Infection of astroglial element s of the pediatric nervous system has been demonstrated and suggests t hat direct infection of some astrocytes may contribute to the neurolog ic deficit. In this model, HIV-1 establishes a persistent state of inf ection in astrocytes, which can be reactivated by the cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta). To better understand the natural history of viral persistence in astro glial cells, We characterized infection at the transcriptional level. The most abundant viral transcript during the establishment of persist ence was the subgenomic multiply spliced 2-kb message, similar to mono nuclear cell models of HIV-1 latency. Following reactivation with TNF- alpha or IL-1 beta the multiply spliced 2-kb message remained the most abundant viral transcript, in contrast to infected mononuclear cells in which reactivation leads to the reemergence of the 9- and 4-kb tran scripts. Further characterization of the persistent 2-kb transcript by PCR amplification of in vitro-synthesized viral cDNA showed that, in the absence of cytokine stimulation, the most abundant multiply splice d transcripts were the Nef- and Rev-specific messages. However, follow ing cytokine stimulation, double- and triple-spliced Tat-, Rev-, and N ef-specific messages could be identified. Immunohistochemical staining demonstrated that, during viral persistence, astrocytes expressed Nef protein but few or no viral structural proteins. These results demons trate that viral persistence in astrocytes at the transcriptional leve l is fundamentally different from that seen in mononuclear cells and c ould account for the virtual absence of astroglial expression of viral structural antigens in vivo.