HIV-1 Vpr and Mucosal Immunopathogenesis

About This Grant

PROJECT SUMMARY Unraveling the basic functional properties of individual HIV-1 proteins could provide important clues relevant towards novel therapies and cure strategies. The functional properties of most HIV-1 proteins had been dissected in great detail, but among the viral `accessory' proteins, HIV-1 Vpr remains enigmatic. HIV-1 Vpr has been linked to diverse phenotypes that include significant effects on apoptosis, cell-cycle arrest, innate immune regulation and latency reactivation by interacting with a multitude of host proteins. Interestingly, Vpr-associated replication phenotypes were most consistent in myeloid cells such as macrophages and dendritic cells, but not in CD4 T cells. These data are puzzling, as in persons with HIV-1 infection (PWH), macrophage-tropic viruses typically do not emerge until later clinical stages. As a highly conserved virion-associated protein, HIV-1 Vpr is expected to exert its effects very early on, when mucosal CD4+ T cells serve as critical cellular infection targets. Specifically, during acute HIV-1 infection, high levels of HIV-1 replication and CD4 T cell depletion in the gastrointestinal (GI) tract contributes to a dysregulated epithelial barrier. The subsequent translocation of bacteria and/or bacterial products from the gut lumen to the underlying lamina propria and systemic circulation leads to persistent inflammation and chronic immune activation that does not resolve with antiretroviral therapy. Recently, HIV-1 Vpr was reported to alter the transcriptome and/or proteome of CD4 T cell lines and mitogen-activated blood CD4 T cells, but without a significant effect on virus replication. We suspect that inconsistencies reported for HIV-1 Vpr function could be due to the use of infection models that may not capture fundamental attributes of early HIV-1 replication in vivo. Previously, we established the Lamina Propria Aggregate Culture (LPAC) model to study the biology of clinically relevant HIV-1 strains in primary immune cell types derived from the GI tract. Using the LPAC model, we observed that Vpr in the context of transmitted/founder HIV-1 had a consistent defect in (Aim 1) replication and (Aim 2) depletion of primary gut CD4 T cells. To begin to decipher the underlying molecular mechanisms, we propose to evaluate critical virological determinants linked to various Vpr functional attributes. Linking unbiased proteomic and transcriptomic approaches with focused strategies to track the replication block, we will pinpoint candidate pathways and molecular partners in gut CD4 T cells for subsequent in-depth analyses. Altogether, this exploratory study promises to expand our understanding of HIV-1 Vpr biology in CD4 T cells, the main cellular targets of HIV-1, and in the process, enrich our understanding of HIV-1 mucosal pathogenesis.