Chemokine-Cytokine Nexus in Fungal Immunity

描述（由申请人提供）：二态真菌，荚膜组织原体（Hc）是美国中西部和东南部特有的。大多数感染是轻微的或无症状的。在免疫正常或免疫抑制的个体中，该有机体建立潜伏状态并可引起危及生命的感染。我们已经证明趋化因子受体CCR2在控制小鼠Hc肺部感染中起着至关重要的作用。这种受体的缺失与感染的加剧和非常规来源-巨噬细胞和树突状细胞-诱导白细胞介素(IL)-4的产生有关。IL-4的中和可恢复免疫力。我们已经获得证据表明，趋化因子CCL7和2（两种CCR2配体）的信号传导在最佳宿主防御中很重要。在下面的建议中，我们将探讨CCR2信号在抑制IL-4生成和促进有效细胞免疫反应中的重要作用机制。具体目标1将检查CCL2和7在宿主防御和炎症中的作用。我们将在原位和体外鉴定产生这些趋化因子的细胞。我们将研究受体或趋化因子的缺失是否会改变酵母细胞的体内驻留。我们将确定CCR2配体是否表现出直接或间接的吞噬细胞激活。在特定目标2中，我们将利用具有与IL-4基因相关的绿色荧光蛋白的小鼠来研究IL-4转录细胞的进化和时间外观。研究将确定Hc是否调节CCR2的表达。我们还将研究巨噬细胞和树突状细胞利用产生IL-4的途径。在具体目标3中，我们将研究CCR2和/或IL-4缺失导致免疫缺陷的机制。我们将评估CCR2缺失促进选择性活化的巨噬细胞或骨髓抑制细胞出现的可能性。我们将确定这两种人群中是否有一种或两种会抑制抗真菌免疫。我们将测试T细胞的功能和扩增情况。我们将评估T细胞在肺部扩张失败的可能性是主动抑制和表面受体调节的结果。这些研究的目的是更好地了解Hc的发病机制，从而提高Hc如何逃避宿主防御的知识。这些发现有助于趋化因子-细胞因子网络在微生物发病机制中的影响，并证明CCL7具有新的作用。

DESCRIPTION (provided by applicant): The dimorphic fungus, Histoplasma capsulatum (Hc) is endemic to the Midwestern and southeastern United States. Most infections are mild or asymptomatic. The organism establishes a latent state and can cause a life-threatening infection in immunocompetent or immunosuppressed individuals. We have shown that the chemokine receptor, CCR2, is critically important in controlling pulmonary infection with Hc in mice. The absence of this receptor is associated with exacerbation of infection and the induction of interleukin (IL)-4 by unconventional sources-macrophages and dendritic cells. Neutralization of IL-4 restores immunity. We have obtained evidence that signaling by the chemokines CCL7 and 2, two CCR2 ligands, are important in optimal host defenses. In the following proposal, we will explore the mechanisms by which CCR2 signaling is important in constraining IL-4 generation and promoting an effective cellular immune response. Specific aim 1 will examine the role of CCL2 and 7 in host defenses and inflammation. We will identify the cells producing these chemokines in situ and ex vivo. We will investigate if the absence of the receptor or the chemokines alters the in vivo residence of yeast cells. We will ascertain if CCR2 ligands manifest a direct or indirect activation of phagocytes. In specific aim 2, we will utilize a mouse that has green fluorescent protein linked to the IL-4 gene to investigate the evolution and temporal appearance of IL-4- transcribing cells. Studies will be performed to determine if Hc modulates expression of CCR2. We also will investigate the pathways that macrophages and dendritic cells utilize to generate IL-4. In specific aim 3, we will examine mechanisms by which the absence of CCR2 and/or IL-4 contributes to defective immunity. We will assess the possibility that the absence of CCR2 promotes the emergence of alternatively activated macrophages or myeloid suppressor cells. We will determine if either or both of these populations dampen antifungal immunity. We will test T cell function and expansion. We will assess the possibility that the failure of T cells to expand in the lungs is consequence of active inhibition as well as modulation of surface receptors. The goal of these studies is to better understand the pathogenesis of Hc, thereby enhancing knowledge of how Hc escapes host defenses. These findings contribute to the influence of the chemokine- cytokine network in microbial pathogenesis and evince a new role for CCL7. PUBLIC HEALTH RELEVANCE: This grant seeks to understand the interaction between two types of soluble mediators known as chemokines and cytokines in host resistance to a fungus that causes human disease, Histoplasma capsulatum. This fungus which is found world-wide is a serious cause of lung infection in both normal humans and those who have impaired immunity. Our work will demonstrate how important it is for appropriate signaling through a surface receptor for a particular chemokine in order that the host can survive.