Inflammasome response to bacterial infection

描述（由申请人提供）：沙门氏菌是发展中国家和发达国家的一个重大公共卫生威胁，可引起伤寒或胃肠炎，最近在撒哈拉以南非洲被观察到是引起社区获得性菌血症的新病原体。沙门氏菌使用毒力因子，包括III型分泌系统，来操纵宿主细胞生理学。先天免疫系统检测感染期间胞质溶胶中的扰动。介导这种检测的胞质模式识别受体的一个重要家族是Nod样受体（NLR）。一些NLR，包括NLRP 3和NLRC 4，形成炎性体，其募集并激活半胱天冬酶-1，半胱天冬酶-1是一种蛋白酶，其随后将炎性细胞因子IL-1和IL-18切割成其成熟的分泌形式。NLRP 3和NLRC 4检测鼠伤寒沙门氏菌感染，并且所产生的胱天蛋白酶-1活化主要通过IL-18的活性降低体内细菌负荷。在本申请中，我们将分析NLRC 4（Aim 1）和NLRP 3（Aim 2）检测的分子决定因素，以及S.鼠伤寒感染NLRC 4响应分泌到巨噬细胞胞质溶胶中的鞭毛蛋白和杆状蛋白。我们将剖析这种检测的分子决定因素，并研究鞭毛蛋白和杆蛋白在体内检测的相对重要性。NLRP 3响应于各种细胞扰动，我们将研究NLRP 3检测吞噬体内未消化细菌的长期存在的假设。我们将比较NLRP 3和NLRC 4检测的解剖定位，检验NLRC 4具有检测S的离散时间窗的假设。NLRP 3检测最近从肠腔迁移的鼠伤寒沙门氏菌，而NLRP 3检测传播后的细菌。最后，我们将定义NK细胞在IL-18应答中的作用。这些研究将提供深入了解先天免疫检测的复杂相互作用，通过两个炎性小体，响应于不同的胞质扰动触发的S。鼠伤寒。本研究结果对减毒活疫苗及疫苗佐剂的设计具有指导意义。这些研究揭示的一般机制也将促进对炎症性疾病的理解。

DESCRIPTION (provided by applicant): Salmonellae are a significant public health threat in both developing and developed countries, causing Typhoid fever or gastroenteritis, and recently have been observed as emerging pathogens causing community acquired bacteremia in sub-Saharan Africa. Salmonellae use virulence factors, including type III secretion systems, to manipulate host cell physiology. The innate immune system detects perturbations in the cytosol during infection. An important family of cytosolic pattern recognition receptors that mediate this detection is the Nod- like receptors (NLR). Some NLRs, including NLRP3 and NLRC4, form inflammasomes that recruit and activate Caspase-1, a protease that subsequently cleaves the inflammatory cytokines IL-1 and IL-18 to their mature, secreted forms. NLRP3 and NLRC4 detect Salmonella typhimurium infection, and the resulting Caspase-1 activation reduces bacterial burden in vivo primarily through the activities of IL-18. In this application, we will analyze the molecular determinants of detection by NLRC4 (Aim 1) and NLRP3 (Aim 2), and the IL-18 response (Aim 3) during S. typhimurium infection. NLRC4 responds to flagellin and rod protein secreted into the macrophage cytosol. We will dissect the molecular determinants of this detection and examine the relative importance of flagellin and rod protein detection in vivo. NLRP3 responds to a variety of cellular perturbations, and we will investigate the hypothesis that NLRP3 detects the prolonged presence of undigested bacteria within the phagosome. We will compare the anatomic localization of NLRP3 and NLRC4 detection, testing the hypothesis that NLRC4 has a discrete window of time to detect S. typhimurium that have recently emigrated from the gut lumen, while NLRP3 detects bacteria after dissemination. Finally, we will define the role of NK cells in the IL-18 response. These studies will provide insight into the complex interplay of innate immune detection through two inflammasomes that respond to different cytosolic perturbations triggered by S. typhimurium. Our results will be instructive for designing live attenuated vaccines as well as vaccine adjuvants. The general mechanisms revealed by these studies will also facilitate the understanding of inflammatory disease.