Delineation of Borrelia burgdorferi motility and chemotaxis in the development of

描述（由申请人提供）：描述伯氏疏螺旋体在莱姆病发展中的运动性和趋化性莱姆病是由螺旋体细菌伯氏疏螺旋体（Bb）引起的，它通过蜱虫传播给人类。这种疾病被归类为一种新出现的传染病，是美国最流行的媒介传播疾病。莱姆病有多种临床表现，包括红斑、皮疹、关节炎、心脏炎和神经系统症状。虽然可以用抗生素治疗，但某些慢性病例甚至对静脉注射抗生素产生更大的耐药性。目前尚无疫苗可用，因此，确定在引起莱姆病中起重要作用的毒力机制对于制定有效的预防/治疗制度至关重要。细菌的运动性和趋化性对许多传染病的发展至关重要。尽管移动性和趋化性相关基因占Bb基因组的6%，但这些基因中的大多数在逃避免疫清除中的作用尚未被描述。值得注意的是，虽然许多细菌中的某些运动性和趋化性突变体被证明在定植过程中传染性较低或延迟，但Bb的类似突变体是非传染性的，并在24-48小时内被小鼠清除，这表明运动性和趋化性对Bb的动物生命周期至关重要。这些发现与提出的感染模型一致，其中蜱虫沉积的细菌迅速识别和适应其新宿主，利用其螺旋体运动性在细胞免疫反应之前迅速传播通过致密的皮肤组织，并利用趋化信号到达免疫特权组织，在那里它们可以长期存在并逃避宿主抗体反应。根据我们的初步结果和已发表的报告，我们假设Bb的运动性和趋化性对Bb的毒力至关重要。长期目标是描述Bb如何利用趋化性和运动性侵入宿主组织并逃避免疫清除，从而导致疾病发展。我们提出了三个具体的目标来验证这一假设：Aim 1将产生7个不同的运动性和趋化性基因的靶向敲除，并在体外描述这些突变体的运动性/趋化性表型。目的2将描述这些突变体在体内的相对传染性，并揭示它们是否能够完成自然的“小鼠-蜱-小鼠”感染周期。目的3将利用多光子显微镜和新的活体成像技术，直接可视化和描述这些突变菌株如何在活小鼠的皮肤组织中表现出基本的毒力特性。总之，这些研究将描述这些基因在Bb毒力中的重要功能和关键作用，并可能确定预防和/或治疗莱姆病的治疗靶点。

DESCRIPTION (provided by applicant): Delineation of Borrelia burgdorferi motility and chemotaxis in the development of Lyme disease Lyme disease is caused by the spirochetal bacteria Borrelia burgdorferi (Bb), which is transmitted to humans by Ixodes ticks. The disease is categorized as an emerging infectious disease and is the most prevalent vector borne disease in the United States. Lyme disease has various clinical manifestations including erythema migrans rash, arthritis, carditis, and neurological symptoms. Though treatable with antibiotics, certain chronic cases are much more resistant, even to intravenous antibiotics. No vaccine is currently available, thus identification of virulence mechanisms that are important in causing Lyme disease is critical for developing effective prevention/treatment regimes. Bacterial motility and chemotaxis are central to the development of many infectious diseases. Although motility- and chemotaxis-associated genes constitute 6% of the Bb genome, a role for most of these genes in escaping immune clearance has not been described. Notably, while certain motility and chemotaxis mutants in many bacteria were shown to be less infectious or delayed in colonization processes, a similar mutant of Bb is non-infectious and cleared by mice within 24-48 hours, indicating motility and chemotaxis are vital for the enzootic life cycle of Bb. These findings agree with the proposed infection model, where tick-deposited bacteria quickly recognize and adapt to their new host, utilize their spirochetal motility to rapidly disseminate through dense skin tissues ahead of the cellular immune responses, and utilize chemotactic signals to reach immunoprivileged tissues where they can persist for long periods and evade the host antibody responses. Based on our preliminary results and published reports, we hypothesize that Bb motility and chemotaxis are essential for Bb virulence. The long term goal is to describe how Bb utilizes chemotaxis and motility to invade host tissues and evade immune clearance, allowing for disease development. Three specific aims are proposed to test this hypothesis: Aim 1 will generate targeted knockouts of 7 different motility and chemotaxis genes, and describe the motility/chemotaxis phenotype of these mutants in vitro. Aim 2 will delineate the relative infectivity of these mutants in vivo and reveal whether they can complete the natural "mouse-to-tick-to-mouse" infection cycle. Aim 3 will utilize multiphoton microscopy and novel intravital imaging techniques to directly visualize and describe how these mutant strains perform essential virulence properties within the skin tissues of living mice. Together, these studies will delineate the important functions and critical roles of each of these genes in Bb virulence and potentially identify targets for therapies to prevent and/or treat Lyme disease.