Delineation of Borrelia burgdorferi motility and chemotaxis in the development of

描述（由申请人提供）：莱姆病发展过程中伯氏疏螺旋体运动性和趋化性的描述莱姆病由螺旋体细菌伯氏疏螺旋体（Bb）引起，通过硬蜱传播给人类。该疾病被归类为一种新出现的传染病，是美国最流行的病媒传播疾病。莱姆病有多种临床表现，包括游走性红斑、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更具抗药性。目前没有疫苗可用，因此鉴定在导致莱姆病中重要的毒力机制对于开发有效的预防/治疗制度至关重要。细菌的运动性和趋化性是许多感染性疾病发展的核心。虽然运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殖过程中感染性较低或延迟，但Bb的类似突变体是非感染性的，并且在24-48小时内被小鼠清除，这表明运动性和趋化性对于Bb的地方性生命周期至关重要。这些发现与所提出的感染模型一致，其中蜱沉积细菌快速识别并适应其新宿主，利用其螺旋体运动性在细胞免疫应答之前通过致密皮肤组织快速传播，并利用趋化信号到达免疫豁免组织，在那里它们可以长期存在并逃避宿主抗体应答。根据我们的初步结果和已发表的报告，我们假设，Bb运动和趋化性是必不可少的Bb毒力。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。提出了三个具体的目标来验证这一假设：目标1将产生7个不同的运动和趋化基因的靶向敲除，并描述这些突变体的运动/趋化表型在体外。目的2将描述这些突变体在体内的相对感染性，并揭示它们是否能够完成自然的“小鼠-蜱-小鼠”感染周期。目标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株如何在活小鼠的皮肤组织内执行基本的毒力特性。总之，这些研究将描述这些基因中的每一个在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。 公共卫生相关性：莱姆病是美国和北方其他地区最常见的蜱传疾病，但目前没有疫苗可用。伯氏疏螺旋体利用其新颖的螺旋体运动性和趋化性特性有效地通过致密宿主组织传播并到达免疫保护性小生境的能力被认为对疾病建立至关重要。这些研究将利用许多靶向突变体来直接描述B的重要性。在蜱和鼠宿主中建立感染的burgdorferi运动性和趋化性基因，希望确定治疗性疗法或疫苗的靶点。

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. PUBLIC HEALTH RELEVANCE: Lyme disease is the most common tick-borne disease in the United States and the rest of the Northern hemisphere, however no vaccine is currently available. The ability of Borrelia burgdorferi to use their novel spirochetal motility and chemotaxis properties to efficiently disseminate through dense host tissues and reach immunoprotective niches are believed to be critical to disease establishment. These studies will utilize a number of targeted mutants to directly delineate the importance of B. burgdorferi motility and chemotaxis genes for establishing infection in both tick and murine hosts, with the hope of identifying targets for curative therapies or vaccines.