Attacking HIV provirus: therapeutic strategies to disrupt persistent infection

The therapeutic armamentarium for human immunodeficiency virus type 1 (HIV-1) infection continues to expand. New targets such as entry and integration have recently been successfully exploited. However, HIV-infected patients in need of treatment are currently committed to lifelong suppressive therapy. The persistence of integrated HIV DNA genomes capable of producing virus is a fundamental obstacle to the eradication or cure of HIV infection. Rational molecular or pharmacologic strategies to eliminate persistent HIV proviral genomes are an unaddressed therapeutic need. Coupled with potent antiretroviral therapy, treatments that could efficiently deplete the persistent DNA reservoir of HIV could radically alter treatment paradigms. Prior attempts to target persistent proviral infection deployed intensive antiretroviral therapy (ART) in combination with global inducers of T-cell activation. Initial trials of this approach were unsuccessful. Non-specific T-cell activation may induce high-level viral replication above a level that can be fully contained by ART, while increasing the susceptibility of uninfected cells. Selective targeting of HIV provirus via agents that induce the expression of quiescent HIV, but have limited effects on the uninfected host cell is an alternate approach to attack latent HIV. Recent studies define the role of repressive chromatin structure in maintaining HIV quiescence, and suggest that mechanisms that remodel chromatin about the HIV promoter are a possible therapeutic target. Other studies have uncovered specific factors that may act to induce or maintain latency by limiting the efficiency of HIV gene expression. Attempts to deplete latent HIV using drugs that alter chromatin structure have entered clinical study.