EXCEED THE SPACE PROVIDED. The primate lentiviral Vpr and Vpx proteins, although dispensable for viral replication in primary lymphocytes, have now been shown to be critical for the infection of macrophages, both in vitro and in vivo. However, the mechanism through which these proteins facilitate viral replication in macrophages is unknown. The goal of this Merit Application is to characterize the mechanism by which these proteins regulate the replication of the virus in macrophages both in vitro and in vivo. Our original suspicion was that these proteins interact with positive cellular factors that are important for a post-entry step in viral replication. Our recent studies suggest that these proteins may counteract the effects of negative cellular factors that restrict viral infection. This, however, does not greatly impact the experimental strategies or design. The studies to be undertaken in the next phase of this Merit Award can be summarized as follows: 1. Characterize cffector domains in the HIV-1 Vpr and SIVsM Vpx proteins that mediate macrophage infection 2. Identify cellular restriction factors that interact with the Vpr-Vpx proteins to impact viral replication. 3. Identify how the cellular restriction factor that is targeted by the Vpr and Vpx proteins influences viral replication and how the Vpr and Vpx proteins counteract its effect. 4. Define the in vivo phenotype of SIVsM Vpx mutants that are unable to counteract the restriction factor. It is expected that these studies will lead to the identification of novel restrictions that counteract primate lentivirus infection and reveal future targets for antiretroviral therapy. PERFORMANCE SITE ========================================Section End===========================================
