Genotypic variation and B. burgdorferi pathogenesis

描述(申请人提供)：莱姆病是美国最常见的节肢动物传播疾病，在过去的十年中，报告的病例数量翻了一番，达到每年20,000多例。莱姆病是由感染了伯氏疏螺旋体的扁虱叮咬引起的，伯氏疏螺旋体是莱姆病的病原体。在过去的资助期间，我们曾测定伯氏杆菌临床分离株的遗传多样性，并发现从皮肤获得的分离株与从血液中获得的分离株的基因分布明显不同。此外，从皮肤样本中容易培养出的特定基因很少从血液中培养出来。这些发现表明，不同的伯氏杆菌基因型具有不同的在受感染宿主中传播的潜力。在初步研究中，我们观察到，人外周血单个核细胞(PBMC)暴露于伯氏杆菌后，可强烈诱导通过Toll样受体(TLR)-7和TLR-9介导的I型干扰素(IFN)反应。此外，缺乏线性质粒的伯氏杆菌菌株变异体，特别是lp36，不能诱导这种反应。我们推测，由lp36编码的一个或多个因子可被吞噬细胞特异性识别，导致吞噬小体内通过TLR7/9信号摄取并随后刺激I型干扰素的产生，伯氏杆菌株诱导I型干扰素反应的能力可能在螺旋体传播中发挥重要作用。在这个修订的应用程序中，我们将结合遗传学、细胞生物学和动物研究来检验这一假设。具体地说，将确定负责产生干扰素-a的lp36编码因子，将确定吞噬细胞对不同伯氏杆菌分离株的相对摄取，并将在小鼠莱姆病模型中探索早期诱导I型干扰素反应与螺旋体传播之间的相关性。本修订申请是为了响应NOTOD-09-058：“NIH宣布恢复法案资金可用于竞争性修订申请”而提交的。拟议的研究明确地建立和扩大了父母补助金的目标，将加快科学研究的节奏，并允许保留工作。他们将阐明感染患者症状发展的基础，以及导致伯氏杆菌在人类中传播的因素--这是父母赠款的核心目标。 公共卫生相关性：莱姆病是美国最常见的节肢动物传播疾病，是由感染了伯氏疏螺旋体的壁虱叮咬引起的，伯氏疏螺旋体是这种疾病的病原体。我们观察到了一条新的、以前未描述的伯氏杆菌TLR7/TLR9介导的信号通路，该通路导致人PBMCs产生高水平的I型IFN，并假设这一反应在螺旋体传播中发挥作用。拟议的研究将阐明感染患者症状发展的基础，以及导致伯氏杆菌在人类中传播的因素。

DESCRIPTION (provided by applicant): Lyme disease is the most commonly reported arthropod-borne disease in the United States and the number of reported cases has doubled to over 20,000 per year during the past decade. Lyme disease is caused by the bite of a tick infected with the spirochete, Borrelia burgdorferi, the etiologic agent of the disease. During previous funding periods, we have determined the genetic diversity among clinical isolates of B. burgdorferi and found a significantly different distribution of genotypes in isolates obtained from skin compared with blood. Furthermore, a particular genotype that is readily cultivated from skin specimens is rarely cultured from blood. These findings demonstrate that different genotypes of B. burgdorferi possess varying potential for dissemination in an infected host. In preliminary studies, we have observed that exposure of human peripheral blood mononuclear cells (PBMCs) to B. burgdorferi results in robust induction of a type I interferon (IFN) response that is mediated through toll-like receptor (TLR)-7 and TLR-9. Furthermore, B. burgdorferi strain variants lacking linear plasmids, in particular lp36, cannot induce this response. We hypothesize that one or more factors encoded by lp36 are specifically recognized by phagocytic cells, leading to uptake and subsequent stimulation of type I IFN production via TLR7/9 signaling from within the phagolysosome and that the ability of a B. burgdorferi strain to induce a type I IFN response may play an important role in spirochetal dissemination. In this revision application we will test this hypothesis by a combination of genetic, cell biology and animal studies. Specifically, the lp36-encoded factor responsible for IFN-a production will be identified, the relative uptake of diverse B. burgdorferi isolates by phagocytic cells will be determined and the correlation between early induction of a type I IFN response and spirochetal dissemination will be explored in a murine Lyme disease model. This revision application is submitted in response to NOTOD- 09-058: "NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications". The proposed studies clearly build and expand on the aims of the parent grant, will accelerate the tempo of scientific research and allow for job retention. They will shed light on the basis for symptom development in infected patients and on the factors contributing to dissemination of B. burgdorferi in humans - a central goal of the parent grant. PUBLIC HEALTH RELEVANCE: Lyme disease, the most commonly reported arthropod-borne disease in the United States is caused by the bite of a tick infected with the spirochete, Borrelia burgdorferi, the etiologic agent of the disease. We have observed a novel and previously undescribed TLR7/TLR9-mediated signaling pathway for B. burgdorferi, which results in the production of high levels of type I IFNs by human PBMCs and hypothesize that this response plays a role in spirochetal dissemination. The proposed studies will shed light on the basis for symptom development in infected patients and on the factors contributing to dissemination of B. burgdorferi in humans.