Murine Typhus: Vector Biology and Transmission

描述(由申请人提供)：我们建议的研究强调几个主要概念，如立克次体毒力问题，不同脊椎动物和无脊椎动物宿主中立克次体的适合性，以及病原体-宿主(蚤/鼠)相互作用的分子动力学。在这个相互竞争的更新应用中，我们建立在最近的成就基础上，现在专注于剖析定义小鼠斑疹伤寒人畜共患病的分子相关性。因此，我们将使用包括立克次体基因组数据挖掘、病原体系统发育分析和实证研究相结合的综合方法来研究立克次体和寄主转录组的模式，并确定寄主关联是否指导立克次体的毒力程度。这一竞争性更新的目的是(1)确定跳蚤免疫反应蛋白是否限制伤寒杆菌的生长(目标I)和(2)从功能上表征一组被确定为对毒力具有潜在作用的立克次体基因(目标II)。该提案的具体目的是为了突出宿主和斑疹伤寒杆菌为确保自身生存而采取的策略。在目标I下，我们将检验跳蚤免疫反应蛋白限制伤寒杆菌生长的假设。为了揭示伤寒杆菌与每个免疫反应蛋白在体内的相互作用，将使用免疫学、生化和分子方法来证明每个免疫反应蛋白的共定位和抗立克次体特性。此外，RNAi将用于确定抑制免疫基因表达是否会影响体内立克次体的生长。在第二个目标下，我们将检验分泌蛋白在立克次体毒力中起主要作用的假设。为了验证这一假设，我们将利用一种综合的方法，包括对伤寒杆菌分泌蛋白的全基因组鉴定和分子分析，以及通过反义RNA技术对选定的潜在毒力基因进行功能分析。项目简介：小鼠斑疹伤寒是一个很好的例子，这种疾病的重要性只有患者才能充分认识到，即使在今天，在世界上大多数地区，他永远不会知道自己得了什么病，因为诊断不会做出。随着农村地区城市化程度的提高，鼠(地方性)斑疹伤寒、老鼠及其跳蚤的病原体之间的密切联系是这种疾病扩展到农村社区的基础。因此，伤寒杆菌不仅由于放松卫生而在世界许多沿海地区重新出现，而且还成为农村动物种群中的一种新的病原体。我们提出的研究通过使用小鼠斑疹伤寒动物模型，强调了立克次体毒力和致病机制的几个主要概念。我们的研究通过提供可用于开发更好的立克次体疫苗和/或疗法的病原体基因产物的信息，促进了对伤寒杆菌生物学的理解。

DESCRIPTION (provided by applicant): Our proposed research underscores several major concepts such as the issue of rickettsial virulence, rickettsial fitness in diverse vertebrate and invertebrate hosts, and molecular dynamics of pathogen-host (flea/rat) interactions. In this competing renewal application, we build upon recent accomplishments, and now focus on dissecting the molecular correlates that define the murine typhus zoonosis. Thus, we will use an integrated approach including the combination of rickettsial genome data mining, pathogen phylogenomic analysis and empirical studies to investigate the patterns of rickettsial and host transcriptome profiles and to define whether host-association directs the degree of rickettsial virulence. The aims of this competitive renewal is to (1) determine if flea immune response proteins limit the growth of R. typhi (Aim I) and (2) functionally characterize a set of rickettsial genes that were identified as having a potential role in virulence (Aim II). The specific aims of the proposal are designed to highlight the strategies employed by both the host and the Rickettsia typhi to ensure their own survival. Under the aim I, we will test the hypothesis that flea immune responsive proteins limit R. typhi growth. To implicate an interaction between R. typhi and each immune responsive protein in vivo, immunological, biochemical and molecular approaches will be used to demonstrate colocalization and anti-rickettsial properties of each immune responsive protein. Additionally, RNAi will be used to determine if suppression of immune gene expression affects rickettsial growth in vivo. Under the second aim we will test the hypothesis that secretory proteins play a cardinal role in rickettsial virulence. In order to assess this hypothesis, we will utilize an integrated approach that includes a genome-wide identification and molecular analysis of R. typhi secretory proteins and functional analysis of selected potential virulence genes by anti-sense RNA technology. PROJECT NARRATIVE: Murine typhus is a good example of a disease whose importance is not adequately appreciated except by the patient, and, even today, in most parts of the world, he will never know what ails him because the diagnosis will not be made. An intimate association between the causative agent of murine (endemic) typhus, Rickettsia typhi, rats and their fleas underlie the expansion of this disease into rural communities as the urbanization of rural settings is on the increase. Thus, R. typhi not only re-emerge in many coastal regions of the world as a result of relaxed hygiene but also become an emerging pathogen in rural animal populations. Our proposed research underscores several major concepts in rickettsial virulence and pathogenesis by using murine typhus animal model. Our research advances the understanding the biology of R. typhi by providing information on pathogen gene products that could be used in developing better rickettsial vaccines and/or therapeutics.