Abstract The goal of proposed experiments in this application is to determine how HIV infection disrupts intestinal barrier function. It is now appreciated that microbial translocation across an impaired epithelial barrier leads to circulating LPS, persistent immune activation and chronic inflammation in people living with HIV (PLWH). These HIV associated effects are important contributors to premature development of neurocognitive disorders, cardiovascular disease, metabolic syndrome and bone abnormalities even in PLWH on optimal combination antiretroviral therapy (cART). Untreated infection is characterized by the production of proinflammatory cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNFα). Following therapy, cytokine levels decline but chronic inflammation continues. Prevention of inflammation-induced comorbidities requires the development of more specific therapeutics targeting the underlying cause. However, a gap exists in our understanding of the underlying molecular pathways involved. This proposal will capitalize on an established collaboration between investigators with expertise in HIV biology and intestinal barrier function/pathobiology. We have generated strong preliminary data that provides a framework for understanding the underlying link between disrupted intestinal epithelial barrier function and HIV infection. While the overall chronic inflammatory manifestations of HIV infection are likely to be multi-factorial, our exciting results support an overarching hypothesis that lamina propria HIV-1 infected primary human CD4+T lymphocytes that closely interact with intestinal epithelial initiate a process leading to enhanced production of pro-inflammatory cytokines that negatively impact epithelial homeostasis resulting in a leaky intestinal barrier. Given these important new insights, funding is requested to support a major collaborative effort between established investigators in the areas of HIV biology and intestinal inflammation/barrier disruption to determine the mechanism(s) through which primary human intestinal epithelial cells (IECs) and HIV-infected primary T cells synergize to cause intestinal pathobiology. Specifically, we will determine the HIV-dependent mechanisms that alter T-cell function and disrupt the intestinal barrier. In addition, we will identify the pathways altered in IECs exposed to HIV infected T-cells that lead to barrier dysfunction. Findings generated from these studies will allow a better understanding of the mechanisms underlying HIV related enteropathy that is known to be a major source of morbidity and mortality in HIV-infected individuals and will lead to development of new strategies to improve the health of HIV infected people. 1