The blockade of transcriptional repression at the HIV LTR allows outgrowth of virus from the resting T cells of aviremic patients.

David M Margolis (1,3), L. Ylisastigui (1), G. Lehrman (1), V.C. Rucker (2), and P.B. Dervan (2). University of Texas Southwestern Medical Center at Dallas, Department of Medicine, Division of Infectious Diseases, Dallas, TX 75390 (1); Department of Chemistry and Chemical Engineering and Beckman Institute, California Institute of Technology, Pasadena, CA 91125 (2); and North Texas Veterans Health Care Systems, Dallas, TX 75216 (3); (USA)

Background: The latent reservoir of HIV-1 within resting CD4⁺ T cells is an obstacle to the long-term treatment of HIV infection.  Without activation, the HIV-1 long terminal repeat (LTR) remains quiescent within these cells.  The host factors LSF and YY1 bind the LTR, recruit histone deacetylase, resulting in inhibition of LTR expression. Material and Methods: To test the biological relevance of this hypothesis we utilized pyrrole-imidazole polyamides, small molecules designed to target specific DNA sequences, which we find can enter the nucleus of primary resting CD4+ cells.  We obtained resting CD4 cells from durably aviremic (< 50 copies/ml) HAART-treated HIV+ patients.  We exposed these cells to LTR-specific polyamides, designed to block repressor action at the HIV promoter. Results: Following exposure to LTR-binding polyamides, replication-competent HIV was recovered from the resting CD4+ cells of 6 of 8 HIV+ patients samples, whereas HIV was recovered in 7 of 8 patient samples following maximal cell activation.  Viral variants recovered as studied by heteroduplex analysis are equally diverse after exposure to polyamides or activation. Conclusions: Specific LTR-binding polyamides derepress integrated but quiescent HIV-1 in resting CD4⁺ cells obtained from HIV⁺ patients, resulting in viral replication and outgrowth.  These findings suggest that host factors restrict LTR expression in primary resting CD4⁺ cells, and therefore may play an important role in the establishment or maintenance of latency.  Therapeutic approaches to disrupt latency in the resting CD4⁺ reservoir of HIV infection targeted to the HIV promoter, without global activation of uninfected T cells, may therefore be considered.  Complementary data using other approaches to derepress HIV and induce viral outgrowth from HIV+ patients’ resting cells will be presented.