The long-term goal of this project is to develop and evaluate strategies for eradication of HIV-1 from infected individuals. These studies will be performed with an animal model that enables comprehensive analyses of viral reservoirs and replication dynamics during HAART. This model utilizes rhesus macaques infected by a chimeric virus of SIVmac239 containing the HIV-1 reverse transcriptase (RT) in place of the SIV RT (RT-SHIV). In this model a three-drug combination that is widely used in humans [efavirenz + (-)-FTC + PMPA] mimics HAART in HIV- 1-infected humans with respect to virus load (VL) suppression and rebound upon cessation of drug therapy. In order to study eradication strategies in the RT-SHIV/macaque model, we have developed a sensitive VL assay with a limit of detection of 1-2 copies of viral RNA (vRNA) per ml of plasma, and have also developed sensitive RT-PCR and PCR assays to measure vRNA and viral DNA (vDNA) in tissues. The goal of this project is to evaluate enhanced HAART in combinations that may more fully suppress plasma and tissue VLs to levels below detection with our sensitive PCR assays. Because a potential limitation of current antiretroviral therapy is access of drugs to key reservoir tissues, we will also determine levels of drugs in target tissues and use that information to optimize drug regimens. In addition to virological endpoints, the impact of these drug combinations will be evaluated in RT-SHIV-infected resting CD4+ lymphocyte populations. Importantly, the highly manipulatable RT-SHIV/macaque model enables assessment of potential clinical impact by determining effects on delay or reduction of viral rebound upon cessation of therapy. The drug combinations we propose are designed to evaluate: i) optimization of DNA chain termination with combinations of four potent nucleoside analogs (NRTI) in combination with efavirenz (NNRTI) or an integrase inhibitor, raltegravir;ii) combinations of the most effective NRTIs with both efavirenz and raltegravir;and iii) enhancement of the most potent drug combination with a protease inhibitor or a CCR5 antagonist. The overall Hypothesis of this project is that an intensified HAART regimen has the potential to eliminate RT-SHIV from infected macaques. These studies will provide insight on the requirements for complete suppression of virus replication in tissues and specific cell types as well as in plasma. Thus, this project aims to determine whether there is a limitation to suppression of residual viremia with antiviral drug combinations and whether eradication will also require """"""""induction"""""""" strategies for reactivation of latent virus.
It is likely that eradication of HIV-1 from infected individuals will require both full suppression of virus replication and the reactivation of latent virus during fully suppressive therapy. The focus of this project is elimination of residual virus replication in cells and tissues. The results will provide important information about the relative contributions of virus replication and other reactivation of latent virus to residual viremia during HAART, the relationship between drug levels and virus suppression in tissues and specific cell types, and the effect of enhanced therapy on latent reservoirs in resting CD4+ T lymphocytes. The results of this study will also contribute to future studies of strategies for eliminate the resting memory T cell reservoir of latent HIV-1. The success of such induction strategies will likely be dependent on the ability of fully suppressive HAART to prevent replication of reactivated virus.
