Innate immune resistance to intracellular bacterial pathogens

描述(由申请人提供)：摘要：这项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。尽管有抗生素，但细菌感染仍然是一个重大的公共卫生挑战。我的研究重点是革兰氏阴性的细胞内病原体嗜肺军团菌，它是一种名为军团病的严重肺炎的病原体。军团菌的毒力取决于它在巨噬细胞内生存和生长的独特能力。之前的研究已经证实，一种名为Naip5的基因有助于协调保护巨噬细胞免受军团菌感染的细胞防御，但Naip5赋予军团菌抵抗力的分子机制在很大程度上仍然是个谜。NAIP5与一个细胞质病原体检测蛋白大家族同源，该家族还包括IPAF、NODS和NALPS。我们的初步结果表明，对军团菌的耐药性依赖于caspase-1介导的细胞死亡的快速激活，这种死亡是在巨噬细胞胞浆中检测到细菌鞭毛蛋白后触发的。因此，这项拨款提案的具体目的是：1.检验Naip5通过启动依赖caspase-1的巨噬细胞快速死亡来限制军团菌生长的假设。2.验证存在检测鞭毛蛋白并诱导巨噬细胞快速死亡的胞浆监视系统的假设。3.利用体外和体内模型建立和鉴定Naip5基因敲除小鼠的表型4.开发一种发光的军团菌菌株，以允许高通量筛选，以鉴定限制(或允许)军团菌生长所需的宿主蛋白。相关性：预计从上述工作中获得的结果将使人们能够更深入地了解细菌是如何致病的，以及哪些因素会导致对这些细菌的成功免疫反应。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.