Although highly active antiretroviral therapy (HAART) is successful to block active replication of HIV in AIDS patients, it does not eradicate viruses. Presence of latent HIV reservoirs remains a major obstacle to the cure. Reactivated viral replication from latency induces cytopathic effects and leads to cell death of reservoir cells. There are several promising small compounds being currently tested for HIV reactivation from latency. However, they are either less potent in vivo or associate with severe toxicity. Recently, it was uncovered that the size of latent HIV reservoirs is much larger than previously estimated, suggesting that a combinatory regimen targeting multiple restrictive mechanisms of HIV latency may be required. Thus, identification of novel gene targets for anti-latency therapy is urgent. Our recent studies o host factors modulating HIV replication identified the bromodomain protein, BRD4, plays an important role in maintaining HIV latency. More importantly, we found that the BRD4 inhibitor, JQ1, is able to synergize with other HIV latency reversers to activate latent HIV in certain cases. These preliminary data suggest that BRD4 is a promising gene target for HIV anti-latency therapy, but the ideal gene to be targeted simultaneously with BRD4 for reaching a better effect remains to be identified. Our recent studies, using an integrated approach to combine proteomic study of host proteins physically associating with HIV TAT protein and genetic results of host proteins regulating HIV replication using RNAi-mediated gene silencing, identified a set of HIV TAT-associated inhibitory proteins (TIPs) that negatively regulate HIV transcription through interacting TAT. In this proposal, we will first verify the role of a small set of TIPs in HIV transcription and latency in primary CD4+ T cells. We will further study their cooperative interactions with BRD4. Genetic interactions of TIPs and BRD4 as well as the physical interactions of TIPs with TAT-LTR elements at HIV latency and reactivation are measured. These data are subjected to computational analyses of this small host network including TAT-LTR, BRD4-P-TEFb, and TIPs.
We aim to identify the kinetically and thermodynamically significant TIPs in this network that can be targeted by small compounds. An in vitro TIP-TAT interaction assay will be developed for high-throughput small compound screens to identify inhibitors that potently disrupt such interaction. These compounds may release the suppressive effect of TIP on TAT activity to allow full activation of HIV transcription, and thus are useful to revert HIV latency. We will evaluate them in both primary cell model of HIV latency as well as the CD8+ T cells depleted peripheral blood mononuclear cells (PBMCs) isolated from HAART-treated AIDS patients. Beneficial effect of these compounds together with BRD4 inhibitor JQ1 will be determined as well to identify better drug pair(s) for HIV anti-latency therapy using JQ1. We believe that our study of novel TIPs will improve our understanding of host machineries controlling HIV transcription and latency, and further target those druggable ones for reverting HIV latency and elimination.
Although the antiretroviral therapy is efficient to treat HIV/AIDS and slow the course of the disease, the presence of HIV latent reservoirs hinders the viral elimination and there is still no cure. We propose to verify the roles of a set of HIV TAT-associated inhibitory proteins (TIPs) in HIV latency in primary T cells and study their cooperative interactions with BRD4 that regulates viral latency and reactivation. For those TIPs with kinetic and thermodynamic significance we will further identify small compounds disrupting TIP-TAT interactions and test their activity to revert latent HIV in reservoir T cells that can be ultimatey eliminated.
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