Cytosolic sensing of intracellular Brucella infection

描述(申请人提供)：布鲁氏菌病是一种传播最广的人畜共患传染病，每年新增病例超过50万例。该病主要由细菌病原体布鲁氏菌和流产布鲁氏菌引起，通过食用未经巴氏灭菌的乳制品或接触受感染的动物而感染。布鲁氏菌病是一种以发热为特征的多系统疾病，通常为骨关节病。由于据估计只有4%的布鲁氏菌病病例被报告，实际数字可能要大得多。该病的一个重要特征是其长期性，这是由于网状内皮系统持续的细菌定植和全身性传播所致。然而，病原体和宿主之间导致成功定植和逃避免疫系统清除的特定相互作用在很大程度上尚不清楚。而布鲁氏菌。似乎缺乏大多数经典的毒力因子，我们的工作表明，编码IV型分泌系统(T4SS)的VIRB基因座对于单核巨噬细胞的生存和小鼠感染模型的毒力是必不可少的。虽然T4SS介导的细胞内持久性的分子机制尚不清楚，但我们最近确定了(I)T4SS的第一个底物，以及(Ii)T4SS在体内触发肉芽肿性炎症的作用。我们的长期目标是确定布鲁氏菌与宿主相互作用导致疾病的分子机制。这项应用的目的是在细胞水平上精确定位T4SS如何与先天免疫信号通路相互作用，以触发有利于定植的反应。这一应用的中心假设是，T4SS通过在感染细胞中引发依赖caspase-1的促炎反应来在宿主中建立一个生态位。中心假设将得到检验，这一应用的目标将通过(1)确定检测细胞内布鲁氏菌感染的胞液传感器和(2)确定分泌的T4SS底物在调节caspase-1炎症小体中的作用来实现。我们期待这项工作的结果将建立T4SS如何引发细胞反应的新范式，以促进布鲁氏菌在其宿主生态位中的建立，从而显著影响推动该领域的概念和方法。 与公共卫生相关：布鲁氏菌是一种细菌病原体，在食用了受细菌污染的未经巴氏灭菌的山羊、绵羊或牛奶的人或职业接触受感染动物的工人中，会导致发热性疾病。在世界范围内，每年有超过50万新的布鲁氏菌病病例。布鲁氏菌引起的发烧尤其令人虚弱，如果治疗不当，在首次感染后可能会复发数年。这项应用旨在确定布鲁氏菌如何能够利用宿主的免疫反应持续存在于免疫系统的受感染细胞和组织中。了解这种病原体如何利用宿主的免疫反应来造福，可能会揭示布鲁氏菌病预防和治疗的新靶点。

DESCRIPTION (provided by applicant): Brucellosis is a one of the most widespread zoonotic infection, with over 500,000 new cases each year. The disease, caused primarily by the bacterial pathogens Brucella melitensis and Brucella abortus, is acquired by consumption of unpasteurized dairy products or by contact with infected animals. Brucellosis is a multisystem disease characterized by fever, and frequently, osteoarticular disease. Since it has been estimated that only 4% of brucellosis cases are reported, the actual number is likely to be much larger. An important feature of the disease is its protracted nature that results from persistent bacterial colonization of the reticuloendothelial system and systemic dissemination. However, the specific interactions between pathogen and host that result in successful colonization and evasion of clearance by the immune system are largely uncharacterized. While Brucella spp. appear to lack most classical virulence factors, our work has shown that the virB locus, encoding a Type IV secretion system (T4SS), is essential for survival in mononuclear phagocytes and virulence in a mouse infection model. While the molecular mechanisms underlying T4SS-mediated intracellular persistence are unknown, we have recently identified (i) the first substrates of the T4SS, and (ii) a role for the T4SS in triggering granulomatous inflammation in vivo. Our long-range goal is to define molecular mechanisms of Brucella interaction with the host that lead to disease. The objective of this application is to pinpoint at the cellular level, how the T4SS interacts with innate immune signaling pathways to trigger a response that is favorable for colonization. The central hypothesis of this application is that the T4SS functions in establishing a niche in the host by eliciting caspase-1 dependent proinflammatory responses in infected cells. The central hypothesis will be tested and the objectives of this application accomplished by (1) Identifying the cytosolic sensors that detect intracellular Brucella infection and (2) Determining the role of secreted T4SS substrates in modulating the caspase-1 inflammasome. We expect that the results of this work will establish new paradigms of how the T4SS elicits cellular responses to promote establishment of Brucella in its host niche, thereby significantly influencing concepts and methods driving the field. PUBLIC HEALTH RELEVANCE: Brucella is a bacterial pathogen that causes a febrile illness in people who have consumed unpasteurized goat, sheep or cow's milk contaminated with the bacteria or in workers occupationally exposed to infected animals. Worldwide, there are over 500,000 new cases of brucellosis each year. The fevers caused by Brucella are particularly debilitating and if not treated properly, can recur for years after the initial infection. This application proposes to determine how Brucella is able to use the host's immune response to persist in infected cells and tissues of the immune system. Understanding how this pathogen exploits the host's immune response to its benefit is likely to reveal new targets for prevention and therapy of brucellosis.