Surface Lipoproteins and Serum Resistance in Borrelia burgdorferi

伯氏疏螺旋体的表面脂蛋白和血清耐药性

• 批准号: 8075005
• 负责人: DARRIN R. AKINS
• 金额: $ 18.14万
• 依托单位: UNIVERSITY OF OKLAHOMA HLTH SCIENCES CTR
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-24 至 2013-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8075005
• 关键词: Bacteria; Binding; Binding Proteins; Blood; Borrelia; Borrelia burgdorferi; Borrelia burgdorferi OspE protein; C3bi; Cell surface; Collaborations; Complement; Complement 3b; Complement Factor H; Complement Inactivators; Congenital neurologic anomalies; Data; Disease; Environment; Family; Generations; Genes; Heart; Immunologic Surveillance; In Vitro; Infection; Joints; Laboratories; Lead; Lipoproteins; Lyme Disease; Mammals; Mediating; Midgut; Mus; Mutate; Neuraxis; Open Reading Frames; Order Spirochaetales; Organism; Pathogenesis; Play; Proteins; Public Health; Reporting; Resistance; Role; Serum; Skin; Suggestion; Surface; System; Therapeutic; Tick-Borne Infections; Ticks; Tissues; United States; Virulence; Virulent; base; cytotoxic; enzootic; in vivo; insight; interest; killings; mouse model; mutant; novel; novel vaccines; outer surface lipoprotein; public health relevance; transmission process

DESCRIPTION (provided by applicant): Lyme disease is caused by spirochetes that have been grouped into three different genospecies, Borrelia burgdorferi, B. afzelii, and B. garinii. Interestingly, all three genospecies seem to populate different niches in the mammalian host during infection. For example, B. burgdorferi and B. afzelii are commonly associated with disease involving the heart, joints, and skin, while B. garinii often causes central nervous system abnormalities. It was recently shown that both B. burgdorferi and B. afzelii bind host serum complement inhibitor factor H on their cell surface, which possibly enhances their resistance to serum. By contrast, most B. garinii isolates do not bind factor H and are killed by mammalian serum. This observation has led to the suggestion that B. garinii organisms persistently infect the central nervous system because it is an environment limited in cytotoxic complement. Recently, several B. burgdorferi outer surface lipoproteins (Osp) were identified by us and others that can bind factor H in vitro. The factor H binding proteins that are most relevant include a family of lipoproteins related to OspE as well as a borrelial surface lipoprotein designated CspA. Consistent with their ability to bind factor H, all of these surface lipoproteins have been shown to enhance serum resistance. We and others have previously reported that expressing the B. burgdorferi strain 297 OspE protein in a serum sensitive B. garinii strain results in increased resistance to serum-mediated killing. We also have shown that mutating the cspA gene in a virulent strain of B. burgdorferi results in a mutant that is exquisitely sensitive to serum-mediated killing. Furthermore, we also have recently shown that CspA expression is required for B. burgdorferi to survive in the midgut of ticks as they engorge on mammalian blood. The combined observations are consistent with our hypothesis that CspA and the OspE surface lipoproteins are integral to serum resistance in B. burgdorferi. To directly examine this underlying hypothesis and further examine the mechanistic role played by these proteins in transmission of B. burgdorferi from the tick to mammal, we propose the following two Specific Aims. In Specific Aim 1 we will use several novel strains we recently generated to examine the role of CspA in virulence and disease pathogenesis using the mouse model of Lyme disease. In Specific Aim 2 we will examine a strain that lacks expression of the OspE-related lipoproteins in both wild type B. burgdorferi and in our CspA mutant strain to better assess their role(s) in serum resistance and Lyme disease pathogenesis during the borrelial enzootic cycle. Finally, in the revised proposal we have included more mechanism-based studies to determine if factor H binding to CspA and OspE actually enhances degradation of C3b to iC3b on the surface of this organism, which is the current dogma in the field. Since our last submission, we have generated interesting data indicating that factor H binding proteins may not enhance generation of iC3b on the surface of B. burgdorferi after all, and we will examine this observation in more detail in our revised Aim 2. PUBLIC HEALTH RELEVANCE: The combined studies could result in the identification of new mechanisms that allow Lyme disease bacteria to evade the initial host immune surveillance system after infection. Information derived from the proposed studies could be used to generate a new vaccine or disease modulating therapeutic for Lyme disease. Given that Lyme disease is the most prevalent tick-borne infection in the United States, unique insight from the proposed studies that could lead to a new vaccine strategy for Lyme disease could greatly benefit overall public health in the United States and abroad.

描述（由申请人提供）：莱姆病是由螺旋体引起的，螺旋体分为三种不同的基因种，伯氏疏螺旋体，阿夫泽利螺旋体和加里尼螺旋体。有趣的是，在感染期间，这三种基因种似乎在哺乳动物宿主中占据不同的生态位。例如，伯氏疏螺旋体和阿氏疏螺旋体通常与涉及心脏、关节和皮肤的疾病有关，而加里尼疏螺旋体通常导致中枢神经系统异常。最近研究表明，B. burgdorferi和B. afzelii都能在细胞表面结合宿主血清补体抑制因子H，这可能增强了它们对血清的抗性。相比之下，大多数加里尼布氏杆菌分离株不结合因子H，被哺乳动物血清杀死。这一观察结果表明，加里尼布氏杆菌持续感染中枢神经系统，因为它是一个限制在细胞毒性补体的环境。近年来，我们等人在体外鉴定了几种能结合H因子的伯氏疏螺旋体外表面脂蛋白（Osp）。最相关的因子H结合蛋白包括与OspE相关的脂蛋白家族以及被称为CspA的螺旋体表面脂蛋白。与它们结合因子H的能力一致，所有这些表面脂蛋白都被证明可以增强血清抵抗力。我们和其他人之前报道过，在血清敏感的B. garinii菌株中表达B. burgdorferi菌株297 OspE蛋白会增加对血清介导的杀伤的抵抗力。我们还表明，突变伯氏疏螺旋体毒力菌株的cspA基因导致突变体对血清介导的杀伤非常敏感。此外，我们最近还表明，当蜱虫吞食哺乳动物血液时，伯氏疏螺旋体需要CspA表达才能在蜱虫的中肠中存活。综合观察结果与我们的假设一致，即CspA和OspE表面脂蛋白是伯氏疏螺旋体血清抗性的组成部分。为了直接检验这一潜在的假设，并进一步研究这些蛋白在蜱虫向哺乳动物传播伯氏疏螺旋体中所起的机制作用，我们提出了以下两个具体目标。在Specific Aim 1中，我们将使用我们最近生成的几种新菌株，使用莱姆病小鼠模型来检查CspA在毒力和疾病发病机制中的作用。在特异性目标2中，我们将研究在野生型伯氏疏螺旋体和CspA突变株中缺乏ospe相关脂蛋白表达的菌株，以更好地评估它们在伯氏疏螺旋体地方性动物循环期间在血清耐药性和莱姆病发病机制中的作用。最后，在修订后的提案中，我们纳入了更多基于机制的研究，以确定因子H与CspA和OspE的结合是否实际上增强了该生物体表面C3b到iC3b的降解，这是目前该领域的教条。自上次提交以来，我们获得了有趣的数据，表明因子H结合蛋白可能不会增强伯氏疏体表面iC3b的生成，我们将在修订后的Aim 2中更详细地研究这一观察结果。