Signal Transduction During Toxoplasma Infection

弓形虫感染期间的信号转导

• 批准号: 7774375
• 负责人: ERIC Y DENKERS
• 金额: $ 37.53万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-15 至 2013-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7774375
• 关键词: Affect; Area; Biochemical; Categories; Cell Communication; Cell surface; Cells; Cessation of life; Dendritic Cells; Down-Regulation; Employee Strikes; Ensure; Failure; Funding; Genes; Goals; Health; Human; Immune system; Immunity; In Vitro; Infection; Inflammation Mediators; Inflammatory; Inflammatory Response Pathway; Interleukin-12; Invaded; Investigation; Lead; Ligands; Mediating; Methods; Molecular; Mus; National Institute of Allergy and Infectious Disease; Natural Immunity; Nature; Organism; Parasites; Pathogenesis; Pathology; Phenotype; Population; Prevention strategy; Production; Public Health; Reporter; Research; STAT3 gene; Signal Pathway; Signal Transduction; Signaling Molecule; TNF gene; Testing; Toll-like receptors; Toxoplasma; Toxoplasma gondii; Toxoplasmosis; Virulence; Work; base; biodefense; cytokine; immune function; immunosuppressed; improved; in vivo; macrophage; microbial; mutant; pathogen; prevent; promoter; response; transcription factor; treatment strategy

DESCRIPTION (provided by applicant): 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 pro-inflammatory cytokine responses. The underlying hypothesis to be tested is that T. gondii possesses molecular mechanisms to subvert host signaling pathways leading to pro-inflammatory cytokine production. Recent work has revealed the ability of Toxoplasma to down-regulate cytokines such as TNF-1 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 pro-inflammatory 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 pro-inflammatory cytokines IL-12 and TNF-1, will be examined. The nature of TNF-1 suppression in infected macrophages is profound. Therefore, we will employ molecular methods to determine how the parasite influences promoter activity of the TNF-1 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-1 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.

描述(申请人提供)：本申请的长期目标是了解细胞内原生动物弓形虫感染的分子发病机制。该寄生虫是免疫抑制人群中的一种重要病原体，被NIAID列为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没有症状的。宿主在感染期间的生存需要强大的1型细胞因子产生，但过度兴奋的反应可能导致宿主病理和死亡。因此，寄生虫和宿主都受益于受调控的促炎细胞因子反应。有待检验的基本假设是，弓形虫具有颠覆宿主信号通路导致促炎细胞因子产生的分子机制。最近的工作揭示了弓形虫在感染细胞内下调细胞因子，如肿瘤坏死因子-1的能力。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作实现的。这项建议的目的是阐明弓形虫颠覆先天免疫系统中促炎症信号级联的机制，特别是在体内感染的细胞中，如巨噬细胞和树突状细胞。将使用细胞和生化方法来确定弓形虫干扰宿主信号转导的点。在这方面，寄生虫诱导的信号分子STAT3的激活将被检测，已知的信号分子STAT3参与了促炎细胞因子IL-12和TNF-1的下调。在感染的巨噬细胞中抑制肿瘤坏死因子-1的本质是深刻的。因此，我们将使用分子方法来确定寄生虫如何影响肿瘤坏死因子-1基因的启动子活性。这项提案的最后部分将集中精力检查寄生虫感染的巨噬细胞和树突状细胞在体内感染小鼠时是否表现出抑制表型。这将使用细胞和免疫学方法来确定体内感染细胞中IL-12和TNF-1的产生，以及它们在体内对定义的Toll样受体配体的反应能力。此外，还将分析巨噬细胞和树突状细胞表达的细胞表面活化标志物。通过这些研究，我们希望获得有关弓形虫如何与宿主先天性免疫系统相互作用的重要信息，从而更深入地了解这种重要的机会性病原体的感染。 项目说明/相关性：该项目与公共卫生的相关性在于，弓形虫感染了全世界30%-80%的人口。虽然通常是一种无症状感染，但由于免疫功能不佳，这种寄生虫会成为一种毁灭性的、有时甚至是致命的感染。该项目将加强我们对寄生虫免疫的了解，从而改进治疗策略。