Signal Transduction During Toxoplasma Infection

项目概要/摘要 本申请的长期目标是了解感染的分子发病机制， 细胞内的弓形虫。寄生虫是免疫抑制的重要病原体 种群，并被NIAID分类为B类生物防御生物。然而，在大多数情况下， 感染这种广泛传播的寄生虫是无症状的。感染期间宿主存活需要强健的1型 细胞因子的产生，但过度旺盛的反应可导致宿主病理和死亡。因此， 寄生虫和宿主受益于受调节的促炎细胞因子应答。潜在的假设是 测试结果表明，T。弓形虫具有破坏宿主信号传导途径的分子机制， 促炎细胞因子的产生。最近的工作揭示了弓形虫能够下调 细胞因子如TNF-？从受感染的细胞内。越来越多的证据表明，这是通过 对宿主细胞内信号级联的复杂操纵。本提案的目的是阐明 弓形虫破坏先天免疫系统中促炎信号级联的机制， 特别是在体内感染靶向的细胞如巨噬细胞和树突细胞内。蜂窝 将采用生物化学方法来确定弓形虫干扰宿主信号的点 转导在这方面，寄生虫诱导的信号分子STAT 3的激活，已知参与了 下调促炎细胞因子IL-12和TNF-β，将被审查。TNF-？ 感染的巨噬细胞中的抑制是深刻的。因此，我们将采用分子方法来确定 寄生虫如何影响TNF-α的启动子活性？基因该提案的最后一部分将集中精力 在检查寄生虫感染的巨噬细胞和树突状细胞是否在感染过程中表现出抑制表型时， 小鼠体内感染。这将使用细胞和免疫学方法来确定IL-12 TNF-？在体内感染细胞中的产生和它们在体内应答确定的Toll样受体的能力 ?配体。此外，巨噬细胞和树突状细胞表达的细胞表面活化标志物将被 分析了从这些研究中，我们期望获得重要的信息，T。弓形虫与宿主相互作用 先天免疫系统，使更深入地了解感染这一重要的机会 病原体项目叙述/相关性 该项目与公共卫生的相关性是，弓形虫感染了30-80%的人类， 全球人口。虽然通常是无症状感染，但寄生虫的免疫功能不佳， 以毁灭性的有时甚至致命的感染形式出现。该项目将提高我们对 对寄生虫的免疫力，从而改善治疗策略。

Project Summary/Abstract The long-term objective of this application is to understand the molecular pathogenesis of infection with the intracellular protozoan Toxoplasma gondii. The parasite is an important pathogen in immunosuppressed populations and is classified by the NIAID as a category B biodefense organism. Nevertheless, in most cases infection with this widespread parasite is asymptomatic. Host survival during infection requires robust Type 1 cytokine production, yet overly exuberant responses can result in host pathology and death. Thus, both parasite and host benefit from regulated proinflammatory cytokine responses. The underlying hypothesis to be tested is that T. gondii possesses molecular mechanisms to subvert host signaling pathways leading to proinflammatory cytokine production. Recent work has revealed the ability of Toxoplasma to down-regulate cytokines such as TNF-? from within infected cells. Increasing evidence indicates this is achieved through sophisticated manipulation of host intracellular signaling cascades. The goal of this proposal is to elucidate mechanisms by which Toxoplasma subverts proinflammatory signaling cascades in the innate immune system, in particular within cells such as macrophages and dendritic cells that are targeted for in vivo infection. Cellular and biochemical methods will be employed to define the points at which Toxoplasma interferes with host signal transduction. In this regard, parasite-induced activation of signaling molecule STAT3, known to be involved in down-regulation of proinflammatory cytokines IL-12 and TNF-?, will be examined. The nature of TNF-? suppression in infected macrophages is profound. Therefore, we will employ molecular methods to determine how the parasite influences promoter activity of the TNF-? gene. The last part of this proposal will focus effort on examining if parasite-infected macrophages and dendritic cells display a suppression phenotype during in vivo mouse infections. This will be accomplished using cellular and immunological methods to determine IL-12 and TNF-? production in infected cells in vivo and their in vivo ability to respond to defined Toll-like receptor ? ligands. In addition, macrophage and dendritic cell expression of cell surface activation markers will be analyzed. From these studies, we expect to gain important information on how T. gondii interacts with the host innate immune system, allowing a deeper understanding of infection with this important opportunistic pathogen. PROJECT NARRATIVE / RELEVANCE The relevance of the project to public health is that Toxoplasma infects between 30-80% of the human population worldwide. While normally an asymptomatic infection, with suboptimal immune function the parasite emerges as a devastating and sometimes lethal infection. This project will enhance our understanding of immunity to the parasite, leading to improved treatment strategies.