Genotypic variation and B. burgdorferi pathogenesis

描述（由申请人提供）：莱姆病是美国最常见的节肢动物传播疾病，报告的病例数量在过去十年中翻了一番，每年超过20,000例。莱姆病是由感染了螺旋体、伯氏疏螺旋体（该病的病原）的蜱虫叮咬引起的。在之前的资助期内，我们已经确定了伯氏疏螺旋体临床分离株的遗传多样性，并发现从皮肤和血液中获得的分离株的基因型分布明显不同。此外，从皮肤标本中容易培养的特定基因型很少从血液中培养。这些发现表明，不同基因型的伯氏疏螺旋体在受感染宿主中具有不同的传播潜力。在初步研究中，我们观察到人外周血单核细胞（PBMCs）暴露于伯氏疏螺旋体导致I型干扰素（IFN）反应的强烈诱导，该反应是通过toll样受体(TLR)-7和TLR-9介导的。此外，缺乏线性质粒的伯氏疏螺旋体菌株变体，特别是lp36，不能诱导这种反应。我们假设lp36编码的一个或多个因子被吞噬细胞特异性识别，通过吞噬溶酶体内部的TLR7/9信号导致I型IFN的摄取和随后的刺激产生，并且伯氏疏螺旋体菌株诱导I型IFN反应的能力可能在螺旋体传播中发挥重要作用。在这个修订应用程序中，我们将通过遗传学，细胞生物学和动物研究的结合来检验这一假设。具体来说，lp36编码的IFN-a产生因子将被确定，吞噬细胞对不同伯氏疏螺旋体分离株的相对摄取将被确定，I型IFN反应的早期诱导与螺旋体传播之间的相关性将在小鼠莱姆病模型中被探索。本修订申请是为了响应NOTOD- 09-058：“NIH宣布为竞争性修订申请提供恢复法案资金”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。它们将揭示受感染患者症状发展的基础，以及导致伯氏疏螺旋体在人类中传播的因素——这是父母资助的一个中心目标。

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.