Epidemic Typhus Pathogenesis

描述（由申请人提供）：流行性斑疹伤寒，也被称为监狱热，监狱热或饥荒热，是由革兰氏阴性细菌拉兹氏立克次体引起的。这种由虱子传播的疾病在历史上造成了毁灭性的广泛流行，特别是在战争、饥荒和恶劣的社会经济条件期间和之后，并且是唯一已知的在长潜伏期后可复发的立克次体病（Brill-Zinsser病）。proproazekii被列为CDC/NIAID B类生物战病原体，在所有已知立克次体物种中首次对其全基因组进行了测序。尽管最近在普罗瓦泽氏弧菌的基因操作方面取得了巨大的进展，但关于与血管内皮相互作用的分子方面的知识仍然处于起步阶段，血管内皮是人类感染过程中首选的细胞类型。内皮细胞，参与宿主防御和炎症的关键免疫反应细胞，也密切参与立克次体感染的表现。根据宿主内皮细胞与proproazekii和R. typhi（地方性斑疹伤寒的病原）的相互作用，我们已经确定了核因子κ B (NF-？B)和应激激活的p38蛋白激酶作为至关重要的调节信号机制，有助于宿主细胞的激活和对感染的反应。本探索性拨款申请的具体目标1旨在确定NF-？B和MAP激酶信号通路，并验证细胞内信号机制的潜在差异决定宿主细胞对强毒的Breinl、弱毒的马德里E和强毒的逆毒的Evir菌株的激活强度。目的2将侧重于建立和描述一种鼠模型，该模型密切模仿人类流行性斑疹伤寒的主要病理特征，即弥散性内皮感染和血管炎症。综上所述，这些研究将解决我们目前对斑疹伤寒立克次体病期间血管内皮与猪瘟弧菌之间的体外和体内相互作用以及“内皮激活”机制的理解中的关键空白。该项目的长期目标是通过鉴定体外激活的特殊血管细胞信号通路，并随后详细分析其参与先天和适应性免疫反应的决定，为全面了解流行性斑疹伤寒的发病机制奠定基础，目的是制定针对靶向干预的独特化疗策略。此外，对类似于人类疾病的小动物感染模型的详细描述将使我们能够确定流行性斑疹伤寒的毒力因素和发病机制的独特特征，扩大我们对体内免疫反应的理解，并测试新型抗生素和候选疫苗的功效。公共卫生相关性：由虱传的普氏立克次体引起的斑疹伤寒流行造成的死亡人数超过了所有战争造成的死亡人数的总和，最近的流行病学证据表明，流行性斑疹伤寒在世界不同地理位置重新出现。由于血管功能障碍和损伤是人类立克次体病并发症的主要病理后遗症，因此获得宿主内皮细胞与不同毒力的普拉兹克氏杆菌菌株之间信号相互作用的定义，以及对小鼠血管播散性感染模型的详细描述，是推进我们对流行性斑疹伤寒发病机制理解的第一步。这将最终导致新的治疗和免疫策略的发展，以对抗这种使人衰弱的立克次体病。

DESCRIPTION (provided by applicant): Epidemic typhus, also known as Gaol fever, Jail fever, or Famine fever, is caused by the Gram-negative bacterium Rickettsia prowazekii. This louse-borne disease has been responsible for devastating widespread epidemics throughout history, especially during and after the wars, famine, and poor socio-economic conditions, and is the only known rickettsiosis that can recur after a long period of latency (Brill-Zinsser disease). R. prowazekii is classified as a CDC/NIAID Category B biological warfare pathogen, the entire genome for which was the first to be sequenced among all known Rickettsia species. Although tremendous strides have recently been made in the genetic manipulation of R. prowazekii, the knowledge of molecular aspects of interactions with the vascular endothelium, the preferred cell type infected during human infections, still remains in its infancy. Endothelial cells, key immunoreactive cells involved in host defense and inflammation, are also intimately involved in the manifestations of rickettsial infections. On the basis of interactions of host endothelial cells with R. prowazekii and R. typhi (the etiologic agent of endemic typhus), we have identified activation of nuclear factor kappa B (NF-?B) and stress-activated p38 protein kinase as critically important regulatory signaling mechanisms that contribute to host cell activation and responses to infection. Specific Aim 1 of this exploratory grant application is designed to define the intensity and kinetics of the activation of NF-?B and MAP kinase signaling pathways after R. prowazekii infection of vascular endothelial cells in vitro and test the hypothesis that potential differences in intracellular signaling mechanisms determine the intensity of host cell activation in response to virulent Breinl versus attenuated Madrid E versus virulent revertant Evir strains of R. prowazekii. Aim 2 will focus on establishing and characterizing a mouse model of R. prowazekii infection that closely mimics the major pathological features, i.e. disseminated endothelial infection and vascular inflammation, of epidemic typhus disease in humans. Taken together, these studies will address critical gaps in our current understanding of in vitro and in vivo interactions between vascular endothelium and R. prowazekii and mechanisms underlying 'endothelial activation' during typhus rickettsioses. The long-term objective of this project is to establish the foundation for comprehensive understanding of epidemic typhus pathogenesis by identifying specialized vascular cell signaling pathways activated in vitro and subsequent detailed analysis of their involvement in determination of innate and adaptive immune responses with an aim to develop unique chemotherapeutic strategies focused at targeted intervention. In addition, detailed characterization of a small animal model of infection akin to disease in humans will allow us to define unique features of virulence factors and pathogenesis of epidemic typhus, to expand our understanding of in vivo immune responses, and to test the efficacy of novel antibiotics and vaccine candidates. PUBLIC HEALTH RELEVANCE: Typhus epidemics due to louse-borne Rickettsia prowazekii have caused more deaths than all the wars combined and recent epidemiological evidence documents the reemergence of epidemic typhus in different geographic locations of the world. Since vascular dysfunction and damage are the major pathologic sequelae responsible for complications of human rickettsial diseases, obtaining a definition of signaling interactions between host endothelial cells and R. prowazekii strains of varying virulence and detailed characterization of a mouse model of disseminated infection of the vasculature represent first major steps in advancing our understanding of pathogenesis of epidemic typhus, which will ultimately lead to the development of novel therapeutic and immunologic strategies to combat this debilitating rickettsial disease.