Highly active antiretroviral therapy (HAART) successfully reduces the viral load to below the limit of detection, but HIV replication resumes soon after patients cease therapy. It is believed that a small subset of persistent HIV- infected resting CD4+ T cells are activated in the absence of HAART and contribute to the rebound in patient viral load. This has led to a new treatment strategy that proposes a combination of latency-purging drugs and HAART, with the expectation that activating HIV-infected resting CD4+ T cells will eliminate the persistent viral reservoir by virus-mediated cell death, by the immune system, and by HAART. Reactivation of HIV latency in resting CD4+ T cells can also be induced nonchemically by heat shock. In ongoing experiments, we have found that heat shock protein 90 (Hsp90) is essential for HIV replication and that heat shock (39.5oC) significantly increases HIV infectivity with a simultaneous increase in Hsp90 protein expression. Similar studies by others suggest that reactivation of HIV latency by heat shock is dependent on Hsp90 expression. HIV latency is maintained in resting CD4+ T cells by suppression of the level of virus- specific proteins. Cellular activation results in production of these host factors, but these proteins need to be activated in order to induce HIV reactivation. The active P-TEFb complex and the NF-?B family of transcription factors are essential for HIV reactivation, and these cellular proteins are activated by the Hsp90 chaperone machinery. Similarly, certain chromatin-remodeling proteins that control HIV latency are activated by Hsp90 and lead to HIV reactivation. The examples mentioned above are part of a larger body of work showing that heat shock, and specifically Hsp90, influence HIV replication. Given these observations, we hypothesize that Hsp90 has a functional role in reactivating HIV latency. This hypothesis will be addressed in the experiments of the following Specific Aims: (1) to study how Hsp90 reactivates HIV latency in resting CD4+ T cells, and (2) to identify Hsp90-interacting proteins that reactivate HIV latency. These studies include expressing Hsp90 in untransformed primary human lymphocytes and analyzing the specific Hsp90-interacting proteins that induce HIV reactivation in latently infected resting CD4+ T cells. This hypothesis will be validated in the humanized NSG-BLT mouse model of HIV latency. The objective of this proposal is to identify Hsp90-interacting proteins that reactivate HIV latency, and analysis of these proteins may reveal novel targets for elimination of the latent HIV reservoir.
The proposed studies are innovative and relevant to public health for the following reasons. First, they may identify an additional mechanism of HIV latency and reactivation and second, they may lead to specific therapeutic strategies for long term remission without treatment or complete eradication of persistent virus and achievement of a full cure for HIV infection and AIDS.