Innate immune resistance to intracellular bacterial pathogens

描述（由申请人提供）：总结：本提案的总体目标是了解哺乳动物细胞如何检测和响应细胞内细菌病原体的存在。尽管使用了抗生素，但细菌感染仍然是一个重大的公共卫生挑战。我的研究集中在革兰氏阴性细胞内病原体嗜肺军团菌，一种严重的肺炎称为军团病的病原体。军团菌的毒力取决于其在巨噬细胞内存活和生长的独特能力。以前的工作已经确定，一种名为Naip 5的基因有助于协调细胞防御，保护巨噬细胞免受军团菌感染，但Naip 5赋予军团菌抗性的分子机制在很大程度上仍然是个谜。Naip 5表现出与胞质病原体检测蛋白的大家族的同源性，所述大家族还包括Ipaf、Nods和Nalps。我们的初步结果表明，军团菌的抗性依赖于激活的快速半胱天冬酶-1介导的细胞死亡，这是在检测到细菌鞭毛蛋白在巨噬细胞胞质溶胶中触发。因此，这项拨款建议的具体目标是：1。为了检验Naip 5通过启动快速半胱天冬酶-1依赖性巨噬细胞死亡来限制军团菌生长的假设。2.测试假设，有一个胞质监视系统，检测鞭毛蛋白和诱导快速巨噬细胞死亡。3.使用体外和体内模型产生和表征Naip 5敲除小鼠的表型4.开发一种明亮发光的军团菌菌株，以允许高通量筛选试验，以鉴定限制（或允许）军团菌生长所需的宿主蛋白质。相关性：预计从上述工作中获得的结果将允许更深入地了解细菌如何引起疾病以及哪些因素导致对这些细菌的成功免疫应答。这些知识应该有助于设计新的抗菌疗法的合理方法。

DESCRIPTION (provided by applicant): Summary: The overall goal of this proposal is to understand how mammalian cells detect and respond to the presence of intracellular bacterial pathogens. Despite antibiotics, bacterial infections continue to present a significant public health challenge. My studies focus on the gram-negative intracellular pathogen Legionella pneumophila, the causative agent of a severe pneumonia called Legionnaires' Disease. The virulence of Legionella depends on its unique ability to survive and grow within macrophages. Previous work has established that a gene called Naip5 is instrumental in orchestrating cellular defenses that protect macrophages from Legionella infection, but the molecular mechanism by which Naip5 confers resistance to Legionella has remained largely mysterious. Naip5 exhibits homology to a large family of cytosolic pathogen-detector proteins that also includes Ipaf, Nods and Nalps. Our preliminary results suggest that resistance to Legionella depends on activation of a rapid caspase-1-mediated cell death that is triggered upon the detection of bacterial flagellin in the macrophage cytosol. Thus, the specific aims of this grant proposal are: 1. To test the hypothesis that Naip5 restricts Legionella growth in by initiating a rapid caspase-1 dependent macrophage cell death. 2. Test the hypothesis that there is a cytosolic surveillance system that detects flagellin and induces rapid macrophage cell death. 3. Generate and characterize the phenotype of a Naip5 knockout mouse using in vitro and in vivo models 4. Develop a brightly luminescent strain of Legionella to permit high throughput screening assays to identify host proteins required for restricting (or permitting) Legionella growth. Relevance: It is anticipated that results obtained from the above work will permit a deeper understanding of how bacteria cause disease and of what factors lead to successful immune responses to these bacteria. Such knowledge should contribute to rational approaches to designing novel antibacterial therapies.