Molecular and Cellular Determinants of Immunity to Histoplasmosis

描述(由申请人提供)： 项目摘要：囊状组织胞浆菌是一种二相性真菌，广泛存在于世界各地，是美国中西部和东南部特有的真菌。这种微生物可以在免疫能力强或免疫抑制的人中引起危及生命的感染。我们已经证明，缺乏趋化因子受体CCR5，增强了小鼠清除HC感染的能力。加速分解与调节性T细胞和白介素17+细胞之间的平衡紊乱有关。缺乏CCR5受体的小鼠表现出肺部调节性T细胞数量的减少和IL-17水平的升高。调节性T细胞的缺乏是多因素的。这些细胞不会从胸腺迁出，而且它们在肺部的增殖能力很差。此外，我们已经证明，CCR5的缺失可以减弱肿瘤坏死因子(TNF)--一种拮抗剂--的有害作用。在这里，我们将探索CCR5信号的缺乏在调节T细胞和IL-17之间的平衡紊乱中起重要作用的机制。具体目标1将调查导致调节性T细胞和IL-17之间失衡的具体机制。我们将培育表达Foxp3-绿色荧光蛋白(GFP)和IL-17-GFP的CCR5-/-小鼠，以跟踪特定细胞群的迁移。我们将调查为什么调节性T细胞没有增殖，以及为什么它们不能从胸腺迁移。我们还将分析这些细胞群体在体内的功能属性。在具体目标2中，我们将分析促进真菌清除的细胞和分子效应。我们将研究CCR5配体在决定清除中的作用，IL-17的直接和间接影响，以及转化生长因子-b和IL-23的作用。在具体目标3中，我们将定义CCR5缺失对缺乏肿瘤坏死因子-α的小鼠有益的机制。我们将1)确定调节性T细胞和IL-17+细胞在缺乏TNF-a的小鼠中的运输，2)阐明特定分子效应器的作用，3)测试CCR5抑制剂是否模拟缺乏CCR5的影响。这些研究的目的是为了更好地了解被激活以对抗HC的宿主防御机制。在缺乏肿瘤坏死因子-a的小鼠中，研究CCR5缺失的有益效果的研究与接受肿瘤坏死因子拮抗剂治疗的进行性组织胞浆菌病的报道尤其相关。我们的发现将有助于更好地理解宿主如何成功地防御组织胞浆菌病。 公共卫生相关性： 这笔赠款旨在了解被称为趋化因子的可溶性介体无法与其受体沟通如何增强宿主清除导致人类疾病的真菌--组织胞浆菌的感染的能力。这种真菌在世界各地都有发现，对正常人和免疫力受损的人来说，都是肺部感染的严重原因。这些研究与退伍军人的人口有关，特别是那些居住在疫区的人，或者那些在训练期间或在海外执行任务时可能接触到这种真菌的人。如果他们出现免疫抑制情况，这些研究将揭示这种真菌是如何攻击的，以及如何对抗它。这些研究可能会为威胁生命的组织胞浆菌病带来新的治疗进展。

DESCRIPTION (provided by applicant): Project Summary The dimorphic fungus, Histoplasma capsulatum (Hc) is found world-wide, and endemic to the Midwestern and southeastern United States. The organism can cause a life- threatening infection in immunocompetent or immunosuppressed individuals. We have shown that the absence of chemokine receptor, CCR5, enhances the ability of mice to clear infection with Hc. Accelerated resolution is associated with a perturbation in the balance between regulatory T cells and interleukin (IL)-17+ cells. Mice lacking the CCR5 receptor manifest a decrement in the number of regulatory T cells in lungs and higher levels of IL-17. The paucity of regulatory T cells is multi-factorial. These cells do not emigrate from the thymus, and they proliferate poorly in the lungs. Moreover, we have demonstrated that the absence of CCR5 attenuates the deleterious effects of tumor necrosis factor (TNF)-a antagonism. Herein, we will explore the mechanisms by which the lack of CCR5 signaling is important in disturbing the balance between regulatory T cells and IL-17. Specific aim 1 will investigate the specific mechanisms that lead to the imbalance between regulatory T cells and IL-17. We will produce CCR5-/- mice that express Foxp3-green fluorescent protein (GFP) and IL-17-GFP to track the migration of specific cells populations. We will investigate why regulatory T cells do not proliferate and why they fail to migrate from the thymus. We also will analyze the functional attributes of these cell populations in vivo. In specific aim 2, we will analyze the cellular and molecular effectors that enhance fungal clearance. We will investigate the role of CCR5 ligands in dictating clearance, the direct and indirect influence of IL-17 and the roles of transforming growth factor-b and IL-23. In specific aim 3, we will define the mechanisms by which the absence of CCR5 is salutary to mice lacking TNF-a. We will 1) determine the trafficking of regulatory T cells and IL-17+ cells in mice lacking TNF-a, 2) elucidate the role of specific molecular effectors, and 3) test if CCR5 inhibitors mimic the effect of the absence of CCR5. The goal of these studies is to better understand the host defense mechanisms that are activated to combat Hc. The studies investigating the salutary effect of the absence of CCR5 in mice lacking TNF-a are particularly germane to reports of progressive histoplasmosis in patients receiving TNF antagonists. Our findings will contribute to a greater understanding of how the host can successfully defend against histoplasmosis. PUBLIC HEALTH RELEVANCE: This grant seeks to understand how the inability of soluble mediators known as chemokines to communicate with their receptor enhances the ability of the host to clear infection with a fungus, Histoplasma capsulatum, that causes human disease. This fungus, which is found world-wide, is a serious cause of lung infection in both normal humans and those who have impaired immunity. These studies are relevant to the veteran's population, especially those who reside in the endemic area or in those who may have been exposed to the fungus during training or in overseas duty. If they develop an immunosuppressive condition, these studies will enlighten how the fungus attacks and how it can be combated. New therapeutic advances for life-threatening histoplasmosis will possibly emerge from these studies.