OmpR and SsrB Regulation of Salmonella Virulence

描述（由申请人提供）： 项目摘要 沙门氏菌感染是世界范围内的主要健康问题。沙门氏菌通过表达位于致病岛上的基因引起疾病。沙门氏菌致病岛-1（SPI-1）上的基因使沙门氏菌能够粘附并侵入上皮细胞，而SPI-2基因是全身感染所必需的。被称为III型分泌系统的专门分泌系统在每个致病岛上编码，其为沙门氏菌提供将效应分子分泌到宿主中的手段，所述效应分子改变宿主功能并促进发病。目前的建议集中在SPI-2基因表达的控制。它是沙门氏菌最关键的毒力决定因素之一，但其转录调控的复杂分子生物学，特别是体内基因表达途径的鉴定，仍然不清楚。我们的研究集中在分子方面定义这些途径。SPI-2基因表达受双组分调控系统SsrAB控制，其表达又受另外的调控网络控制，包括EnvZ-OmpR双组分系统、转录激活因子SlyA和全局阻遏物H-NS。SPI-2的复杂调控需要整合多种环境信号，以确保这些重要的毒力基因在巨噬细胞吞噬体内的适当时间表达。在这个建议中，关键的顺式和反式调控元件的ssrA/ssrB在各种环境条件下的表达将被确定。我们假设OmpR位于该调节层级的顶部，激活ssrA/B双组分调节系统的转录。SsrB刺激编码在感染期间分泌的III型分泌器和效应物的基因的表达。在巨噬细胞感染期间，SsrB被NO应激修饰，将在小鼠巨噬细胞、巨噬细胞样细胞系和小鼠组织中检查这种半胱氨酸修饰对SPI-2基因表达的影响，所述小鼠巨噬细胞、巨噬细胞样细胞系和小鼠组织在用沙门氏菌属野生型和ssrB突变株感染后。由于我们的研究，我们将有一个增强的理解，发生作为沙门氏菌感染的结果，以及这些修改如何改变宿主的基因表达的分子事件。 公共卫生相关性： 对退伍军人健康的影响 退伍军人患有急性和慢性细菌感染。我们的研究是机制性的，其影响超出了沙门氏菌，延伸到其他病原体。OmpR已被证明是霍乱弧菌、志贺氏菌、耶尔森氏菌和其他感染性物种中的毒力所必需的。此外，耐药性沙门氏菌感染是所有医院的一个问题，包括退伍军人医院，沙门氏菌引起的败血症是免疫受损的艾滋病毒阳性患者的一个问题，退伍军人的发病率很高。沙门氏菌相关急性胃肠炎是旅行者、部署的军事人员和高人口密度封闭社区（例如军事基地、医院或疗养院）中发病的重要原因。全世界每年伤寒病例超过3300万例，仍然是以前接种疫苗的旅行者和军事人员的潜在担忧。

DESCRIPTION (provided by applicant): PROJECT SUMMARY Salmonella infections are a major health problem worldwide. Salmonella causes disease by expressing genes that are located on pathogenicity islands. Genes that reside on Salmonella Pathogenicity Island-1 (SPI-1) enable Salmonella to adhere to and invade epithelial cells, whereas SPI-2 genes are required for systemic infection. Specialized secretory systems termed type III secretion systems are encoded on each pathogenicity island that provide Salmonella with the means to secrete effector molecules into the host that alter host functions and promote pathogenesis. The present proposal focuses on the control of SPI-2 gene expression. It is one of the most critical virulence determinants of Salmonella, yet the complex molecular biology of its transcriptional regulation, in particular the identification of the pathways for gene expression in vivo, remains poorly defined. Our research is focused on defining these pathways in molecular terms. SPI-2 gene expression is controlled by a two-component regulatory system SsrAB, whose expression is in turn controlled by additional regulatory networks, including the EnvZ-OmpR two-component system, the transcriptional activator SlyA and the global repressor H-NS. The complex regulation of SPI-2 requires integration of multiple environmental signals to ensure that these important virulence genes are expressed at the appropriate time within the macrophage phagosome. In this proposal, critical cis and trans regulatory elements for ssrA/ssrB expression under a variety of environmental conditions will be identified. We hypothesize that OmpR lies at the top of this regulatory hierarchy, activating transcription of the ssrA/B two-component regulatory system. SsrB stimulates expression of the genes encoding the type III secretory apparatus and effectors that are secreted during infection. SsrB is modified by NO stress during macrophage infection, the consequences of this cysteine-modification to expression of SPI-2 genes will be examined in both mouse macrophages, a macrophage-like cell line and mouse tissues upon infection with Salmonella wild type and ssrB mutant strains. As a result of our studies, we will have an enhanced understanding of the molecular events that occur as a result of Salmonella infection and how these modifications alter gene expression in the host. PUBLIC HEALTH RELEVANCE: Impact on Veteran's Health Veterans suffer from both acute and chronic bacterial infections. Our studies are mechanistic and have implications beyond Salmonella, extending to other pathogens. OmpR has been shown to be required for virulence in Vibrio cholerae, Shigella, Yersinia and other infectious species. Furthermore, drug-resistant Salmonella infections are a problem in all hospitals, including VA hospitals and septicemia due to Salmonella is a problem in immune-compromised HIV positive patients, a high incidence which occurs in veterans. Salmonella-associated acute gastroenteritis is a significant cause of morbidity among travelers, deployed military personnel and high population density closed communities (e.g. military bases, hospitals or nursing homes). The number of typhoid fever cases exceeds 33 million per year worldwide and remains a potential concern among previously vaccinated travelers and military personnel.