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: 8511547
• 负责人: Kevin R. Macaluso
• 金额: $ 34.09万
• 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 2015-08-24
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8511547
• 关键词: Adhesions; Amblyomma; Binding Proteins; Biological; Biological Assay; Competence; Dermacentor; Ecology; Epidemiology; Event; Fever; Fluorescent in Situ Hybridization; Generations; Genetic Transcription; Goals; Health; Horizontal Disease Transmission; Human; Immune; Individual; Infection; Kinetics; Laboratories; Mediating; Modeling; Molecular; Nature; Pathogenicity; Protein Binding; Proteins; RNA; 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; 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（由申请人提供）：立克次体是美国最严重的蜱传疾病之一的病原体。立克次体致病性和蜱传播途径（水平和垂直）的复合因素影响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蜱传播立克次体的核心分子机制。尽管自然界中蜱与多种立克次体有重叠分布，但单个蜱种并未感染多种立克次体。因此，正在测试的广泛假设是，斑疹热群（SFG）立克次体的成功水平和垂直传播需要独特的蜱源因子。初步证据表明立克次体传播取决于适当的蜱/立克次体关系和立克次体的致病性质。我们还知道，蜱虫会对感染性立克次体做出积极反应。然而，蜱源性分子的调节对于立克次体在蜱内的存活所需的程度尚不清楚。因此，本提案的实验重点是描绘蜱/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，并通过对不同蜱和立克次体物种的比较分析来定义与立克次体感染相关的蜱源分子。先前未定义的蜱/立克次体相互作用参数将在以下具体目标中确定。 1) 表征致病性和非致病性 SFG 立克次体在蜱宿主体内的水平和垂直传播。先前未知的六种 SFG 立克次体的传播动力学将在 Amblyomma 和 Dermacentor 蜱中进行评估。将使用蜱感染的实验室模型来确定立克次体从感染立克次体的蜱到脊椎动物宿主的水平传播。将通过荧光原位杂交和定量实时 PCR (qPCR) 评估立克次体的垂直传播效率，并评估 SFG 立克次体携带对蜱适应性的影响。 2) 检查典型和非典型蜱/立克次体感染过程中蜱衍生分子和 SFG 立克次体之间的相互作用。蛋白质-蛋白质相互作用测定将用于鉴定整个蜱组织中存在的立克次体结合蛋白。研究将利用配对的蜱组织和 SFG 立克次体进行比较性下拉和蛋白质结合测定。我们将通过生物测定（包括粘附/入侵阻断测定、免疫/抗菌活性评估和 RNA 介导的干扰 (RNAi)）来鉴定关键蜱蛋白并描述它们在立克次体建立中的作用。还将评估各个立克次体物种对特定分子的利用。公共卫生相关性 尽管蜱虫与多种立克次体物种重叠分布，但在自然界中，单个蜱虫物种不会感染多种立克次体物种。我们将研究蜱/立克次体关系的特异性，并描述斑疹热立克次体蜱媒介能力的分子机制，以更好地了解蜱传立克次体疾病的生态学和流行病学。