Dissecting Innate Immune Responses to Salmonella Enteritidis

项目摘要和摘要 肠沙门氏菌是美国食源性住院的主要原因。沙门氏菌 肠杆菌包括2500多个循环亚种或血清型，这些亚种或血清型会引起从自身到 将胃肠炎限制为严重的全身性疾病和死亡。沙门氏菌致病性和宿主的研究 对沙门氏菌的免疫反应依赖于有限数量的常用参考肠杆菌血清型 鼠伤寒杆菌(STM)或伤寒杆菌株。虽然这些研究已经定义了宿主的基本机制- 沙门氏菌之间的相互作用，它们不能反映沙门氏菌之间广泛的基因或表型多样性 这表明我们在理解宿主对沙门氏菌的反应方面存在着一个重要的差距。先天是如何 免疫系统对其他沙门氏菌血清型的识别和响应尤其令人感兴趣，因为它是一种重要的 部分疾病是由伤寒或鼠伤寒以外的血清型引起的。先天免疫系统扮演着 在宿主抵抗感染中起着至关重要的作用，因此是一个特别吸引人的研究目标。 沙门氏菌入侵并在巨噬细胞内复制，并利用保守的III型分泌系统 由称为沙门氏菌致病岛2(SPI-2)的基因组区域编码，以注入毒力因子， 称为“效应器”，进入宿主细胞质。这些效应器操纵宿主环境并允许 沙门氏菌维持细胞内的生态位。SPI-2效应器显示血清内和血清间遗传 多样性，这是宿主对感染反应的重要差异。虽然效应器很重要 对于细菌的毒力，它们还使宿主能够检测到细胞内的细菌。先天的一种机制 免疫识别涉及胞质先天免疫传感器，检测细菌配体或 胞浆内激活炎性caspase-1和/或-11的效应器(CASP1/11)。CASP1/11乳沟 并激活IL-1家族细胞因子和致孔蛋白Gasdermin-D(GSDMD)，导致 炎性细胞死亡称为上睑下垂。CASP1/11是常见的上睑下垂所必需的 研究了鼠伤寒沙门氏菌的菌株。有趣的是，与之前的研究不同，我的初步研究表明 包括肠炎链球菌在内的多个不同血清型的肠杆菌临床分离株首次触发CASP1/11- 独立的GSDMD裂解、IL-1释放和细胞死亡。此外，我的初步研究进一步 证明肠炎沙门氏菌和其他临床分离株在SPI中诱导这种不依赖CASP1/11的细胞死亡。 2-依赖方式。这些数据以及本提案中讨论的其他初步调查结果， 提出肠炎沙门氏菌具有独特的SPI-2效应因子的假设，该效应因子可触发 Casp8介导的上睑下垂。在这项提案中，我的目标是定义介导CASP1/11的宿主途径- 临床分离的沙门氏菌引起的独立细胞死亡(目标1)，与细菌因素(S)有关 触发细胞死亡(目标2)。拟议的项目将扩大我们对沙门氏菌的了解 对当前流行菌株的致病机理和宿主反应。

Project Summary and Abstract Salmonella enterica is the leading cause of food-borne hospitalizations in the United States. The Salmonella enterica species includes over 2500 circulating sub-species, or serovars, which cause disease ranging from self- limiting gastroenteritis to severe systemic disease and death. Studies of Salmonella pathogenicity and host immune responses to Salmonella rely on a limited number of commonly used reference S. enterica serovar Typhimurium (STm) or Typhi strains. While these studies have defined fundamental mechanisms of host- Salmonella interactions, they do not reflect the broad genotypic or phenotypic diversity among Salmonella enterica species, suggesting a crucial gap in our understanding of host responses to Salmonella. How the innate immune system recognizes and responds to other Salmonella serovars is of particular interest, as a significant fraction of disease is caused by serovars other than Typhi or Typhimurium. The innate immune system plays a crucial role in host defense against infection, and therefore represents a particularly attractive target for study. Salmonella invades and replicates within macrophages and utilizes a conserved type III secretion system encoded by a genomic region termed the Salmonella Pathogenicity Island 2 (SPI-2), to inject virulence factors, known as ‘effectors’, into the host cytosol. These effectors manipulate the host environment and permit Salmonella maintenance of an intracellular niche. SPI-2 effectors display intra- and inter-serovar genetic diversity, which contributes to important differences in host responses to infection. While effectors are important for bacterial virulence, they also enable the host to detect intracellular bacteria. One mechanism of innate immune recognition involves cytosolic innate immune sensors that detect bacterial ligands or the activity of effectors within the cytosol which activate the inflammatory caspases -1 and/or -11 (Casp1/11). Casp1/11 cleave and activate IL-1 family cytokines and the pore-forming protein Gasdermin-D (GSDMD), leading to an inflammatory cell death termed pyroptosis. Casp1/11 are necessary for pyroptosis in response to commonly studied strains of S. Typhimurium. Intriguingly, in contrast to prior studies, my preliminary studies show for the first time that multiple S. enterica clinical isolates of different serovars, including S. Enteritidis, trigger Casp1/11- independent GSDMD cleavage, IL-1 release, and cell death. Moreover, my preliminary studies further demonstrate that S. Enteritidis, and other clinical isolates, induce this Casp1/11-independent cell death in a SPI- 2-dependent manner. These data and as well as additional preliminary findings discussed in this proposal, provoke the hypothesis that Salmonella Enteritidis possesses a unique SPI-2 effector which triggers Casp8-mediated pyroptosis. In this proposal, I aim to define the host pathways mediating Casp1/11- independent cell death in response to clinical Salmonella isolates (Aim 1), and the bacterial factor(s) responsible for triggering this cell death (Aim 2). The proposed project will expand our understanding of Salmonella pathogenesis and host-responses to currently circulating strains.