INTERSPECIFIC COMPETITION BETWEEN RICKETTSIAE IN TICKS

蜱中立克次体之间的种间竞争

• 批准号: 7082927
• 负责人: Abdu F Azad
• 金额: $ 25.38万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7082927
• 关键词: Ixodes; Rickettsia; Rickettsia rickettsii; Rocky Mountain spotted fever; SDS polyacrylamide gel electrophoresis; arthropod borne communicable disease; comorbidity; complementary DNA; disease vectors; electron microscopy; epizootiology; genetic library; host organism interaction; immunocytochemistry; intracellular transport; laboratory mouse; polymerase chain reaction; restriction fragment length polymorphism; southern blotting; virulence; western blottings

DESCRIPTION (provided by applicant): Our preliminary studies and those of others clearly demonstrate a dominance of a single species of spotted fever group rickettsiae in ixodid tick vectors, Dermacentor variabilis and D. andersoni. Extensive tick surveys in Montana, Ohio, California, and Maryland revealed the dominance of nonpathogenic rickettsiae in tick populations. The presence of nonpathogenic tick symbionts may account for the low infection rates of Rickettsia rickettsii in D. andersoni and D. variabilis thus resulting in patchy distribution of human cases of Rocky Mountain spotted fever in the US. This project was initiated to investigate the molecular consequences and epidemiological significance of multiple rickettsial infections in ticks. We have proposed that the interactive effects between obligate intracellular rickettsiae within individual ticks may be of sufficient relevance and magnitude to alter the vector competence of ticks. Thus, we have focused on rickettsial symbionts acquired transovarially by D. variabilis ticks, namely Rickettsia montanensis and R. peacockii. We have investigated the prevalence and relative efficiency of transovarial interference of R. montanensis within D. variabilis ticks as mediated by R. rhipicephali. We have also focused on the D. variabilis genes that are differentially expressed in response to rickettsial infection within tick ovarian tissues. We have constructed several tissue-specific cDNA libraries from infected and uninfected D. variabilis. For the renewal application, we are proposing to further refine and characterize molecular mechanisms underlying transovarial interference. Studies under first aim define the functional role of identified molecules that initiate the exclusion of secondary rickettsial infections of tick ovaries. The second aim will be focused on investigating the role of the selected tick molecules in the maintenance and transmission of rickettsiae.

描述(申请人提供)：我们的初步研究和其他人的研究清楚地表明，斑点热群立克次体的单一物种在硬蜱媒介变种革螨和安德森革螨中占主导地位。在蒙大拿州、俄亥俄州、加利福尼亚州和马里兰州进行的广泛的壁虱调查显示，非致病性立克次体在壁虱种群中占主导地位。非致病性硬蜱共生体的存在可能解释了立克次体在安德森和变种立克次体中的低感染率，从而导致美国落基山斑点热人病例的斑块分布。该项目的启动是为了调查硬蜱中多重立克次体感染的分子后果和流行病学意义。我们已经提出，个体硬体内专性细胞内立克次体之间的相互作用可能具有足够的相关性和大小，以改变硬体的媒介能力。因此，我们将重点放在由变种立克次体--蒙丹立克次体和孔雀立克次体--获得的共生体上。我们调查了由Rhipicephali介导的蒙丹根结线虫在变色丝虫体内的经卵干扰的流行率和相对效率。我们还重点研究了在扁虱卵巢组织中因立克次体感染而差异表达的变种杜氏菌基因。我们已经从感染和未感染的变种石杉中构建了几个组织特异性的cDNA文库。对于更新换代的应用，我们建议进一步提炼和表征潜在的经卵巢干扰的分子机制。第一个目标下的研究确定了识别的分子的功能作用，这些分子启动了对硬体卵巢的继发性立克次体感染的排除。第二个目标将集中于研究选定的壁虱分子在立克次体的维持和传播中的作用。