Project Summary Tuberculosis (TB), the leading cause of death due to an infectious disease, is faced by a number of challenges, one of which is our inability to predict disease outcome after exposure. The limited knowledge on risk factors for TB progression and the mechanisms by which these promote susceptibility limits the ability to develop new prevention and treatment approaches. Recently, our collaborators have identified moderate, subclinical vitamin A deficiency as a substantial risk factor for developing active TB, carrying a 10-fold higher risk when serum levels of the intermediate vitamin A metabolite, retinol, are below 200 µg/L. While vitamin A is known to play a critical role in immunity from innate function to polarization of antigen specific T cells, the contribution of vitamin A to protection from active TB disease has only been minimally explored. The substantial TB risk carried by deficiency in vitamin A highlights the need to understand the mechanisms by which this molecule contributes to protection, particularly in the context of malnutrition among TB-affected communities. Vitamin A functions through nuclear receptors that are ligand-activated transcription factors. Other nuclear receptors beyond vitamin A receptors have been shown to regulate immune function and contribute to response to M. tuberculosis infection, including PPARg, a nuclear receptor with obligatory association with vitamin A receptors. Because we have shown that rosiglitazone, an activator of PPARg, improves outcome of tuberculosis in guinea pigs, we hypothesize that that availability of vitamin A and PPAR ligands together influence the transcriptional outcome of TB and consequently, the ability to control infection. The goal of this research is to better understand the contribution of nuclear receptor-ligand interaction, and the impact of impaired vitamin A availability on immune response, control of bacterial growth, and TB disease outcome. These will be investigated through Aims using bone marrow-derived macrophage cell models and a guinea pig model of vitamin A deficiency, both developed in our laboratory. We will first determine the contribution of ligand activation of nuclear receptor heterodimers to transcriptional and microbicidal response to infection with M. tuberculosis in bone marrow macrophages through a combination of validated knock-down techniques targeting vitamin A (RAR, RXR) and PPARg receptors, alongside ligand agonists, all-trans retinoic acid (RAR), 9-cis retinoic acid (RXR), and thiazolidenones (PPARg). This will be followed by the use of our recently developed guinea pig model of dietary vitamin A deficiency to determine the impact of vitamin A and PPARg signaling on TB immunity. Guinea pigs with sufficient, partially deficient, and completely...