Inflammasome response to bacterial infection

描述（由申请人提供）：沙门氏菌在发展中国家和发达国家都是一个重大的公共卫生威胁，引起伤寒或肠胃炎，最近在撒哈拉以南非洲被观察到作为新出现的病原体引起社区获得性菌血症。沙门氏菌利用毒力因子，包括III型分泌系统，来操纵宿主细胞生理学。先天免疫系统在感染期间检测到细胞质中的扰动。介导这种检测的一个重要细胞质模式识别受体家族是Nod样受体（NLR）。一些nlr，包括NLRP3和NLRC4，形成炎性小体，招募和激活Caspase-1， Caspase-1是一种蛋白酶，随后将炎症细胞因子IL-1和IL-18切割成成熟的分泌形式。NLRP3和NLRC4检测鼠伤寒沙门氏菌感染，由此产生的Caspase-1激活主要通过IL-18的活性来减少体内细菌负荷。在本应用中，我们将分析鼠伤寒沙门氏菌感染期间NLRC4 （Aim 1）和NLRP3 （Aim 2）检测和IL-18应答（Aim 3）的分子决定因素。NLRC4响应巨噬细胞胞浆分泌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，并检查鞭毛蛋白和杆状蛋白检测在体内的相对重要性。NLRP3对各种细胞扰动作出反应，我们将研究NLRP3检测吞噬体内未消化细菌长期存在的假设。我们将比较NLRP3和NLRC4检测的解剖定位，验证NLRC4有一个离散的时间窗口来检测最近从肠腔迁移的鼠伤寒沙门氏菌，而NLRP3检测传播后的细菌的假设。最后，我们将定义NK细胞在IL-18反应中的作用。这些研究将深入了解先天免疫检测的复杂相互作用，通过两种炎症小体对鼠伤寒沙门氏菌引发的不同细胞质扰动作出反应。我们的研究结果将对减毒活疫苗和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有助于理解炎症性疾病。

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.