Inflammasome response to bacterial infection

说明(申请人提供)：沙门氏菌在发展中国家和发达国家都是一个严重的公共卫生威胁，会引起伤寒或胃肠炎，最近在撒哈拉以南非洲被观察到是导致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，来操纵宿主细胞的生理。先天免疫系统在感染过程中检测到胞浆中的扰动。介导这种检测的一个重要的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，招募并激活Caspase-1，这是一种蛋白酶，随后将炎性细胞因子IL-1？和IL-18裂解成成熟的、分泌的形式。NLRP3和NLRC4检测到鼠伤寒沙门氏菌的感染，由此产生的Caspase-1激活主要通过IL-18的活性减少体内的细菌负荷。在这个应用中，我们将分析NLRC4(Aim 1)和NLRP3(Aim 2)检测的分子决定因素，以及在鼠伤寒沙门氏菌感染过程中IL-18的反应(Aim 3)。NLRC4对分泌到巨噬细胞胞浆中的鞭毛蛋白和杆状蛋白作出反应。我们将剖析这种检测的分子决定因素，并检查体内鞭毛蛋白和杆状蛋白检测的相对重要性。NLRP3对各种细胞扰动做出反应，我们将调查NLRP3检测到吞噬体内长期存在未消化细菌的假设。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出的鼠伤寒沙门氏菌的假设，而NLRP3在传播后检测细菌。最后，我们将确定NK细胞在IL-18反应中的作用。这些研究将通过两个炎症体对鼠伤寒沙门氏菌引发的不同胞浆扰动做出反应，从而深入了解先天免疫检测的复杂相互作用。我们的结果将对设计减毒活疫苗和疫苗佐剂具有指导意义。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-1ß 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.