The impact of antiretroviral therapy represents a major demonstration of the capability and success of modern drug discovery, development, and implementation. Nevertheless, in infected individuals this success lasts only as long as adherence to the regimen is maintained. Discontinuation of treatment results in viral rebound, necessitating the chronic, lifelong administration of antiretroviral therapy. The requirement for lifelong therapy results from the inability to deplete the persistent reservoir of latently infected cells. The admittedly ambitious ultimate goal of this application is to purge the latently infected reservoir with the objective of eradicating the infection or minimizing the HIV reservoir sufficiently to attain durable immunologic control. This Program Project has been designed with three Projects and two Scientific Cores. Project 1 will identify and characterize potent histone deacetylase inhibitors for the initial studies, while using a human genome siRNA library to identify additional targets for small molecule intervention. These treatment strategies will be systematically evaluated in the following models: (1) the in vitro model of latently infected primary human CD4 lymphocytes developed in our laboratory (Project 2), (2) CD4 lymphocytes obtained ex vivo from chronically infected, HAART-suppressed patients (project 2), and (3) an SIV/Rhesus macaque model (Project 1). Latent infection will be quantified by the two scientific cores. The Molecular Virology Core will measure infectivity, HIV (SIV) nucleic acid species including integrated DNA, and ability of CD4 lymphocytes to express p24 (p27) upon activation. The Molecular Imaging Core (Haase lab) will quantify and characterize infection in antiretroviral drug-suppressed cells from the in vitro HIV model and from macaque tissues. While assessing treatment efficacy and minimizing toxicity, potential collateral immunological consequences of these interventions targeted to host functions will be systematically characterized in Project 3. This highly coordinated, collaboration which ranges from target and drug discovery through animal model proof-of-concept will reveal new insights regarding the pathogenetic mechanisms of HIV latency;however, the goal of the Program Project is to cure AIDS, PROJECT 1: (Hazuda, D) PROJECT 1 DESCRIPTION (provided by applicant): The long term goal of therapy for HIV-1 infection should be to develop treatment regimens either to provide durable control of viral replication and/or eradicate the infection. Among the limitations of current therapy are the incomplete suppression of viral replication in many patients and the inability to affect the latent population of HIV-1 in quiescent CD4+ T-lymphocytes. While new agents in development may enhance the potency and durability of antiretroviral treatments, these will not address the longer term problem of latency. The current program application proposes to evaluate the hypothesis that histone deacetylase (HDAC) inhibitors or other LTR-activating compounds can affect latent infection in a rhesus macaque model of retroviral latency. This hypothesis is based on in vitro observations suggesting that HIV-1 latency is maintained by cellular mechanisms that control chromatin structure and that derepression of HIV-1 transcription can be induced by HDAC inhibitors without activating T-cells. In Project 1 of the application, we will identify and provide inhibitors as well as carry out a genome-scale siRNA screen to identify LTR-suppressing factors to identify different pathways for derepressing HIV-1 transcription. Additionally, we will develop critical assays required to establish an SIV model to test this hypothesis and support the evaluation of the HDAC inhibitor, vorinostat, and other LTR activators in vivo. The objectives of Project 1 include providing potent integrase inhibitors for a novel combination regimen (ART) that will be effective in SIV infection, providing vorinostat and other LTR-activating compounds and evaluating their effects on SIV latency, establishing pharmacodynamic assays for HDAC activity that will be used to select doses and identifying novel LTR-activators with enhanced potency and selectivity for testing in this model. The objective is to assess the susceptibility of the latent reservoirs to therapeutic intervention with the ultimate goal of identifying inhibitors and establishing treatment paradigms suitable for clinical testing.
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