Salmonella-induced Cytopathology in Human Macrophages

描述(由申请人提供)：本研究项目的目标是确定严重播散性沙门氏菌感染背后的细菌毒力因子和巨噬细胞宿主反应。非伤寒沙门氏菌是食源性疾病的常见原因，播散性感染导致相当大的发病率和死亡率。我们对沙门氏菌如何引起肠外疾病的了解有限。本项目关注人类巨噬细胞与沙门氏菌两个主要基因座的蛋白产物之间的宿主-病原体相互作用：SPV基因座是传播的关键毒力决定因素，以及沙门氏菌致病岛SPI-2。Spv操纵子编码SpvB蛋白，这是一种修饰肌动蛋白单体的腺苷二磷酸转移酶。SPI-2编码一种细菌III型分泌系统，当沙门氏菌在细胞内时，该系统特别活跃。其具体目的是：1)确定沙门氏菌对人巨噬细胞的细胞毒作用所需的细菌毒力基因。2)分析细菌效应物诱导细胞病变的机制，包括细胞凋亡。3)探讨巨噬细胞吞噬沙门氏菌时Toll样受体(TLR)信号转导途径及其对丝裂原活化蛋白激酶(MAPK)通路的影响。假设在吞噬过程中，沙门氏菌脂多糖(LPS)触发TLR-4介导的细胞信号通路，刺激p38MAPK，导致最初的细胞凋亡抑制。这为生物体在细胞内增殖提供了时间。SpvB分泌然后分解细胞肌动蛋白，启动细胞程序性死亡。这会触发细胞表面的定位标记，以供其他未感染的巨噬细胞吞噬，从而促进沙门氏菌的传播。我的长期目标是获得一份全职学术任命，对病原体进化为克服巨噬细胞先天免疫反应的分子遗传机制进行独立研究。该项目由加州大学圣迭戈分校的导师指导，并辅以研究生课程，将提供细菌分子遗传学、信号转导分析和巨噬细胞凋亡方面的培训。

DESCRIPTION (provided by applicant): The goal of this research project is to define the bacterial virulence factors and macrophage host responses underlying serious, disseminated Salmonella infection. Non-typhoid Salmonella are common causes of food born illness, disseminated infection causes substantial morbidity and mortality. Our understanding of how Salmonella produces extra-intestinal disease is limited. This project focuses on the host-pathogen interaction between human macrophages and the protein products of 2 major Salmonella loci: the spv locus, a critical virulence determinant of dissemination, and the Salmonella Pathogenicity Island, SPI-2. The spv operon encodes SpvB protein, an ADPribosyl transferase, which modifies actin monomers. SPI-2 encodes a bacterial type III secretion system specifically active when Salmonella are intracellular. The specific aims are: 1)To define bacterial virulence genes required for Salmonella-induced cytotoxicity in human macrophages. 2)To analyse the mechanisms bacterial effectors use to induce this cytopathology, including apoptosis. 3)To determine the Toll-like receptor (TLR) signaling and effect on Mitogen Activated Protein Kinase (MAPK) pathways when macrophages phagocytose Salmonella. The hypothesis is that on phagocytosis, Salmonella lipopolysaccaride (LPS) triggers a TLR-4 mediated cell signaling pathway, stimulating p38 MAPK, causing initial inhibition of apoptosis. This allows time for the organism to proliferate, intracellularly. SpvB secretion then breaks down cellular actin, and programmed cell death is initiated. This triggers cell surface localization markers, for phagocytosis by other uninfected macrophages, facillitating Salmonella spread. My long term objective is to gain a full-time academic appointment to conduct independent research on molecular genetic mechanisms pathogens have evolved to over come macrophages innate immune responses. The project outlined, guided by mentors at UCSD and supplemented by graduate courses, will provide training in bacterial molecular genetics, signal transduction analysis, and apoptsis in macrophages.