XIX International AIDS Conference


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TUAA0201 - Oral Abstract

Unique regulatory mechanisms of CNS-derived HIV-1 LTRs associated with latency

Presented by Lachlan Gray (Australia).

L. Gray1,2, D. Cowley1,3, E. Crespan1, C. Welsh1,4, C. Mackenzie1,5, P. Gorry1,3,6, S. Wesselingh1,7, M. Churchill1,3,4

1Burnet Institute, Centre for Virology, Melbourne, Australia, 2Monash University, Department of Biochemistry and Molecular Biology, Clayton, Australia, 3Monash University, Department of Medicine, Clayton, Australia, 4Monash University, Department of Microbiology, Clayton, Australia, 5Monash University, Department of Immunology, Melbourne, Australia, 6The University of Melbourne, Department of Microbiology and Immunology, Melbourne, Australia, 7South Australian Health and Medical Research Institute, Adelaide, Australia

Background: HIV-1 penetrates the central nervous system (CNS) during early infection, establishing a viral reservoir. While macrophages and microglia represent the sites of productive HIV-1 infection, astrocytes undergo a restricted/latent infection. We recently demonstrated that astrocytes are extensively infected and may therefore constitute a significant potential reservoir of HIV-1 within the CNS. Here, we analyzed HIV-1 promoters (LTR) from matched CNS and non-CNS compartments to determine their role in virus restriction within CNS-derived cells. Determining the regulatory mechanisms of CNS-derived LTRs is essential to understanding the CNS as a HIV-1 viral reservoir, and in developing strategies aimed at HIV-1 eradication.
Methods: HIV-1 LTR sequences from a cohort of HIV-1 autopsy subjects consisting of matched CNS- and non-CNS-derived isolates were examined and their activity was determined in T-cells and SVG astrocyte cells. Electrophoretic mobility shift assays (EMSA) were used to analyze transcription factor binding activity within the core and basal promoter regions of the LTR.
Results: CNS-derived LTRs demonstrated restricted basal transcriptional activity in both T-cells and SVG cells, and non-CNS-derived LTRs showed decreased activity in SVG cells. Restricted basal activity mapped to the three Sp binding motifs, previously shown to be essential for both Tat-independent and Tat-dependent activation of the LTR in T-cells. Further repression in astrocytes was observed due to elevated levels of the repressor Sp3 in SVG cells.
Conclusions: The reduced transcriptional activity observed for CNS-derived HIV-1 promoters was found to correlate with a reduction in Sp1 binding, which mapped to mutations within the core Sp binding motif. Transcriptional activity in SVG cells was further regulated by Sp3, which outcompeted Sp1 for Sp-motif binding. These data suggest that CNS-derived viruses have a reduced capacity to initiate viral transcription in astrocytes and highlights that unique transcriptional mechanisms exist within the CNS, ultimately affecting the fate of viral infection and the development of latency.

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