Molecular and Cellular Determinants of Immunity to Histoplasmosis

描述（由申请人提供）： 二型真菌荚膜组织胞浆菌（Histoplasma capsulatum，Hc）在世界范围内都有发现，并且是美国中西部和东南部的特有种。该微生物可在免疫功能正常或免疫抑制的个体中引起危及生命的感染。我们已经表明，趋化因子受体CCR 5的缺乏，增强了小鼠清除HC感染的能力。加速消退与调节性T细胞和白细胞介素（IL）-17+细胞之间平衡的扰动有关。缺乏CCR 5受体的小鼠表现出肺中调节性T细胞数量减少和IL-17水平升高。调节性T细胞的缺乏是多因素的。这些细胞不会从胸腺中迁移出来，并且它们在肺中增殖不良。此外，我们已经证明，CCR 5的缺乏减弱了肿瘤坏死因子（TNF）-α拮抗作用的有害影响。在此，我们将探讨CCR 5信号传导的缺乏在扰乱调节性T细胞和IL-17之间的平衡方面的重要机制。具体目标1将研究导致调节性T细胞和IL-17之间失衡的具体机制。我们将产生表达Foxp 3-绿色荧光蛋白（GFP）和IL-17-GFP的CCR 5-/-小鼠，以跟踪特定细胞群的迁移。我们将研究为什么调节性T细胞不增殖，为什么它们不能从胸腺迁移。我们还将在体内分析这些细胞群的功能属性。在具体目标2中，我们将分析增强真菌清除的细胞和分子效应物。我们将研究CCR 5配体在指示清除中的作用，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CCR 5的缺失对缺乏TNF-α的小鼠有益的机制。我们将1）确定缺乏TNF-α的小鼠中调节性T细胞和IL-17+细胞的运输，2）阐明特异性分子效应物的作用，和3）测试CCR 5抑制剂是否模拟CCR 5缺乏的效果。这些研究的目的是更好地了解宿主的防御机制，被激活，以打击HC。在缺乏TNF-α的小鼠中调查缺乏CCR 5的有益效果的研究与接受TNF拮抗剂的患者中进行性组织胞浆菌病的报道特别密切相关。我们的研究结果将有助于更好地了解宿主如何成功地抵御组织胞浆菌病。 公共卫生相关性： 这项资助旨在了解被称为趋化因子的可溶性介质如何无法与其受体沟通，从而增强宿主清除导致人类疾病的真菌组织胞浆菌感染的能力。这种真菌在世界各地都有发现，是正常人和免疫力受损者肺部感染的严重原因。这些研究与退伍军人群体有关，特别是那些居住在流行地区或在训练或海外服役期间可能接触过真菌的人。如果他们出现免疫抑制状况，这些研究将揭示真菌如何攻击以及如何对抗。从这些研究中可能会出现危及生命的组织胞浆菌病的新的治疗进展。

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.