INTERSPECIFIC COMPETITION BETWEEN RICKETTSIAE IN TICKS

描述（由申请人提供）：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种在硬蜱载体中占优势，可变革蜱和革蜱。安德森尼。在蒙大拿州、俄亥俄州、加州和马里兰州进行的广泛蜱调查显示，非致病性立克次体在蜱虫种群中占主导地位。非致病性蜱类共生体的存在可能是立克次体感染率较低的原因。andersoni和D.因此，导致美国落基山斑疹热人间病例呈片状分布。本项目旨在研究蜱类立克次体多重感染的分子后果和流行病学意义。我们已经提出，专性细胞内立克次体在个别蜱虫之间的相互作用可能是足够的相关性和幅度，改变蜱虫的载体能力。因此，我们重点研究了D经卵巢获得的立克次体共生体。variabilis蜱，即山地立克次体（Rickettsiamontanensis）和R.孔雀。我们调查了R. montanensis在D. variabilis ticks，由R.裂头兽我们还关注了D。变异体基因在蜱卵巢组织内对立克次体感染的应答中差异表达。我们从感染和未感染的D.变量对于更新申请，我们建议进一步完善和表征跨卵巢干扰的分子机制。第一个目标下的研究确定了启动排除蜱卵巢继发立克次体感染的已鉴定分子的功能作用。第二个目标将集中在调查的作用，选择蜱分子的维护和传播立克次体。

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.