Molecular basis for spotted fever group Rickettsia vector competence in ticks

蜱中斑疹热群立克次体载体能力的分子基础

• 批准号: 7735597
• 负责人: Kevin R. Macaluso
• 金额: $ 37万
• 依托单位: LOUISIANA STATE UNIV A&M COL BATON ROUGE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-20 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7735597
• 关键词: Adhesions; Amblyomma; Binding Proteins; Biological; Biological Assay; Competence; Dermacentor; Ecology; Epidemiology; Event; Fever; Fluorescent in Situ Hybridization; Generations; Genetic Transcription; Goals; Horizontal Disease Transmission; Human; Immune; Individual; Infection; Kinetics; Laboratories; Mediating; Modeling; Molecular; Nature; Pathogenicity; Protein Binding; Proteins; RNA Interference; Rickettsia; Rickettsia Infections; Rickettsia rickettsii; Role; Route; Specificity; Spottings; Testing; Tick Infestations; Tick-Borne Diseases; Ticks; Time; Tissues; Translating; United States; Vertical Disease Transmission; Virulence; antimicrobial; base; comparative; fitness; in vivo; in vivo Bioassay; in vivo Model; interest; novel strategies; pathogen; prevent; protein protein interaction; public health relevance; receptor; transmission process; vector

DESCRIPTION (provided by applicant): Rickettsia rickettsii is the causative agent of one of the most severe tick-borne diseases in the United States. The compounding factors of rickettsial pathogenicity and route of tick transmission (horizontal and vertical) influence the ecology and epidemiology of human rickettsioses. Our long term goal is to elucidate the molecular mechanisms that are central to rickettsial transmission by ticks. Despite the overlapping distribution of ticks with multiple Rickettsia species in nature, individual tick species are not infected with a diverse range of rickettsial species. Therefore, the broad hypothesis being tested is that unique tick-derived factors are required for successful horizontal and vertical transmission of spotted fever group (SFG) Rickettsia. Preliminary evidence indicates rickettsial transmission is dependent on the appropriate tick/Rickettsia relationship and the pathogenic nature of the Rickettsia. It is also known that ticks actively respond to the infecting rickettsiae; however, the extent to which modulation of tick-derived molecules is required for rickettsial survival within the tick is not known. Thus, the experimental focus of this proposal is to delineate the specificity of tick/Rickettsia relationships, the relationship between rickettsial pathogenicity and transmission, and to define the tick-derived molecules associated with rickettsial infection via comparative analysis of different tick and Rickettsia species. The previously undefined parameters of tick/Rickettsia interactions will be determined in the following specific aims. 1) Characterize the horizontal and vertical transmission of pathogenic and nonpathogenic SFG Rickettsia in tick hosts in vivo. The previously unknown kinetics of transmission for six species of SFG Rickettsia will be assessed in Amblyomma and Dermacentor ticks. Horizontal transmission of rickettsiae from Rickettsia-infected ticks to vertebrate hosts will be determined using a laboratory model of tick infestation. The efficiency of vertical transmission of Rickettsia will be assessed by fluorescence in situ hybridization and quantitative real-time PCR (qPCR) and the influence of SFG Rickettsia carriage on tick fitness will be assessed. 2) Examine the interaction between tick-derived molecules and SFG Rickettsia during infection in typical and atypical tick/Rickettsia relationships. Protein-protein interaction assays will be used to identify rickettsial binding proteins present in whole tick tissues. Studies will utilize paired tick tissues and SFG rickettsiae in comparative pull-down and protein binding assays. We will identify key tick proteins and delineate their role in the establishment of Rickettsia via bioassays including adhesion/invasion blocking assays, immune/antimicrobial activity assessment, and RNA-mediated interference (RNAi). The utilization of specific molecules by individual species of Rickettsia will also be assessed. PUBLIC HEALTH RELEVANCE Despite the overlapping distribution of ticks with multiple Rickettsia species, in nature, individual tick species are not infected with a diverse range of rickettsial species. We will examine the specificity of tick/Rickettsia relationships and delineate the molecular mechanisms of tick vector competence for spotted fever Rickettsia to better understand the ecology and epidemiology of tick-borne rickettsial diseases.

描述(申请人提供)：立克次体是美国最严重的壁虱传播疾病之一的病原体。立克次体致病性的复合因素和硬蜱传播途径(水平和垂直)影响着人类立克次体病的生态学和流行病学。我们的长期目标是阐明壁虱传播立克次体的核心分子机制。尽管在自然界中，硬蜱与多种立克次体重叠分布，但个别硬壳类不会感染不同种类的立克次体。因此，正在检验的广泛假设是，斑点热群立克次体的成功水平和垂直传播需要独特的壁虱来源因子。初步证据表明，立克次体的传播取决于适当的立克次体/立克次体关系和立克次体的致病性质。人们还知道，壁虱对感染的立克次体有积极的反应；然而，壁虱来源的分子在多大程度上需要调节，才能使立克次体在壁虱体内存活，这一点尚不清楚。因此，这项建议的实验重点是通过比较分析不同种类的硬蜱和立克次体，来描述硬质立克次体/立克次体关系的特异性，立克次体致病性和传播之间的关系，并确定与立克次体感染相关的硬质来源分子。以前未定义的壁虱/立克次体相互作用参数将在以下具体目标中确定。1)描述致病性和非致病性SFG立克次体在体内宿主体内的水平和垂直传播特征。先前未知的六种SFG立克次体的传播动力学将在Amblyomma和Dermacentor ticks中进行评估。立克次体从感染立克次体的壁虱向脊椎动物宿主的水平传播将使用壁虱感染的实验室模型来确定。将通过荧光原位杂交和定量实时聚合酶链式反应(QPCR)评估立克次体垂直传播的效率，并评估SFG立克次体携带对硬蜱适合性的影响。2)在典型和非典型的硬体/立克次体关系中，检查感染过程中硬体来源的分子与SFG立克次体之间的相互作用。蛋白质-蛋白质相互作用分析将被用来鉴定存在于整个硬蜱组织中的立克次体结合蛋白。研究将利用成对的扁虱组织和SFG立克次体进行比较下拉和蛋白质结合分析。我们将通过包括黏附/侵袭阻断试验、免疫/抗菌活性评估和RNA介导的干扰(RNAi)在内的生物测定，识别关键的壁虱蛋白，并描述它们在立克次体建立过程中的作用。还将评估个别立克次体对特定分子的利用。与公共卫生相关尽管硬体与多种立克次体重叠分布，但在自然界中，个别硬体不会感染多种立克次体。为了更好地了解硬质立克次体疾病的生态学和流行病学，我们将研究硬质立克次体/立克次体关系的特异性，并描述斑点热立克次体的硬质媒介能力的分子机制。