Analysis of interacellular host defenses in Salmonella pathogenesis

描述(申请人提供)：肠道沙门氏菌对世界各地的人和动物健康造成相当大的负担。为了了解这种细胞内病原菌的发病机制和调节宿主防御的寄主因素，人们已经做出了重大努力。临床和实验证据已经明确地证明，CD4+T细胞和IFN3对于预防非伤寒沙门氏菌引起的全身疾病至关重要。IFN3可能在抵抗这种细胞内细菌方面发挥不同的功能，包括激活巨噬细胞的抗菌库。最近的研究表明，IFN3与沙门氏菌配体具有协同作用，可以增强iNOS的转录。由此产生的高NO合成介导了IFN3诱导的巨噬细胞大部分深刻而持久的抗沙门氏菌活性。然而，IFN3激活的NO合成增强巨噬细胞抗沙门氏菌活性的分子机制(S)仍然很大程度上是未知的。我们已经产生了生化和遗传学证据来支持这样一个模型，在该模型中，介导全球沙门氏菌致病岛2(SPI2)转录的SSRB反应调节因子C203是活性氮物种(RNS)的重要目标。这项应用的目的是确定RNS介导的SPI2转录抑制的分子机制。假设没有同系物通过SSRB反应调节因子二聚化结构域的(-SNO)C203抑制SPI2的转录。具体地说，我们建议1)确定RNS介导的使SSRB调节功能失活的修饰；2)在沙门氏菌抗亚硝化防御的背景下检查SPI2的功能；3)选择使SSRB信号对RNS不敏感的SSRB变异等位基因；以及4)表征对二聚化至关重要的SSRB残基。与公共卫生相关的肠炎沙门氏菌对世界范围内的人和动物健康构成相当大的负担。沙门氏菌病的发病机制尚不完全清楚。这项拟议的研究将阐明宿主病原体之间的相互作用，这些相互作用调节着一种毒力因子的表达，而这些毒力因子是沙门氏菌导致人类疾病的关键。

DESCRIPTION (provided by applicant): Salmonella enterica represents a considerable burden to human and animal health worldwide. A significant effort has been made to understand the pathogenesis of this intracellular pathogen and the host factors that mediate host defense. Clinical and experimental evidence have unequivocally demonstrated that CD4+ T cells and IFN3 are critical for preventing systemic disease by non-typhoidal Salmonella. IFN3 likely exerts diverse functions in resistance to this intracellular bacterium, including the activation of the antimicrobial arsenal of macrophages. Recent studies have indicated that IFN3 synergizes with Salmonella ligands to enhance the transcription of iNOS. The resultant high NO synthesis mediates most of the profound and long-lasting anti-Salmonella activity of IFN3-primed macrophages. The molecular mechanism(s) by which IFN3- activated NO synthesis enhances the anti-Salmonella activity of macrophages remains, however, largely unknown. We have generated biochemical and genetic evidence in support of a model in which C203 of the SsrB response regulator that mediates global Salmonella pathogenicity island 2 (SPI2) transcription is an important target of reactive nitrogen species (RNS). The goal of this application is to identify the molecular mechanisms underlying the RNS-mediated repression of SPI2 transcription. It is hypothesized that NO congeners repress SPI2 transcription by S-nitrosylating (-SNO) C203 of the dimerization domain of the SsrB response regulator. Specifically, we propose to 1) determine the RNS-mediated modifications that inactivate SsrB regulatory functions; 2) examine SPI2 function in the context of Salmonella antinitrosative defenses; 3) select for ssrB variant alleles that render SsrB signaling insensitive to RNS; and 4) characterize SsrB residues critical for dimerization. PUBLIC HEALTH RELEVANCE Salmonella enterica represents a considerable burden to human and animal health worldwide. The mechanisms underlying the pathogenesis of salmonellosis are incompletely understood. The proposed research will shed light on the host pathogen interactions that modulate the expression of a virulence factors key to the ability of Salmonella to cause human disease.