Modulation of immunity to tuberculosis through vitamin A-dependent nuclear receptors

项目摘要 结核病（TB）是传染病导致死亡的主要原因，面临着许多挑战， 其中之一是我们无法预测暴露后的疾病结果。对危险因素的认识有限， 结核病的进展及其促进易感性的机制限制了开发新的结核病药物的能力。 预防和治疗方法。最近，我们的合作者已经确定了中度，亚临床维生素 缺乏作为发展活动性结核病的一个重要风险因素，风险高出10倍。大幅 缺乏维生素A所带来的结核病风险强调了了解这一机制的必要性。 分子有助于保护，特别是在结核病影响社区营养不良的情况下。 维生素A通过核受体发挥作用，核受体是配体激活的转录因子。其他核 维生素A受体以外的受体已被证明可以调节免疫功能，并有助于应答 对m说肺结核感染。特别是，过氧化物酶体增殖物激活受体γ，一种与维生素A强制性结合的核受体， 受体在巨噬细胞中富集并影响TB期间的免疫应答。因为我们已经证明 罗格列酮，一种过氧化物酶体增殖物激活物γ的激活剂，改善豚鼠结核病的预后，我们假设， 维生素A和过氧化物酶体增殖物激活受体配体的可用性共同影响结核病期间的转录结果， 因此，控制感染的能力。这项研究的目的是为了更好地了解 核受体-配体相互作用，以及维生素A可用性受损对免疫应答的影响， 细菌生长和结核病的结果。这些将通过Aims使用骨髓进行研究- 衍生的巨噬细胞模型和豚鼠模型的维生素A缺乏症，都是在我们的研究中开发的。 实验室我们将首先确定核受体异源二聚体的配体活化对 转录和杀微生物反应感染M.骨髓巨噬细胞中的结核病。这 该方法使用了针对维生素A（RAR，RXR）和PPAR γ的经验证的敲低技术的组合 受体和维生素A转化酶RALDH，以及配体激动剂，全反式视黄酸（RAR）， 9-顺式维甲酸（RXR）和噻唑烷酮（PPAR γ）。随后将使用我们最近开发的 饮食维生素A缺乏的豚鼠模型，以确定维生素A和过氧化物酶体增殖物激活受体γ信号传导对 肺结核免疫。维生素A充足或严重缺乏的豚鼠将接受或不接受 罗格列酮，一种特异性的PPAR γ激动剂，基于我们之前在豚鼠中对这种药物的评估， 免疫应答和疾病结果。完成这些实验后，我们将 确定了维生素A和核受体控制对感染反应的影响， 结核病结果。这些结果将指导新的宿主导向疗法的开发，以最大限度地降低风险， 改善结核病流行地区暴露结果。

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. 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, which 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. In particular, PPARγ, a nuclear receptor with obligatory association with vitamin A receptors is enriched in macrophages and influences the immune response during TB. Because we have shown that rosiglitazone, an activator of PPARγ, improves outcome of tuberculosis in guinea pigs, we hypothesize that that availability of vitamin A and PPAR ligands together influence the transcriptional outcome during 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. This approach uses a combination of validated knock-down techniques targeting vitamin A (RAR, RXR) and PPARγ receptors, and the vitamin A converting enzyme RALDH, alongside ligand agonists, all-trans retinoic acid (RAR), 9-cis retinoic acid (RXR), and thiazolidenones (PPARγ). 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 PPARγ signaling on TB immunity. Guinea pigs with sufficient or severely deficient vitamin A status will be treated with or without rosiglitazone, a specific PPARγ agonist, based on our previous assessment of this drug in guinea pigs and immune response and disease outcome measured. Upon completing these experiments, we will have determined the impact of vitamin A and nuclear receptor control over response to infection and consequently, TB disease outcome. These results will guide development of new host-directed therapies to minimize risk and improve outcome of exposure in TB-endemic regions.