Structure-Function of Borrelia Surface Lipoproteins

疏螺旋体表面脂蛋白的结构-功能

基本信息

批准号：
7061554
负责人：
WOLFRAM R ZUECKERT
金额：
$ 7.35万
依托单位：
UNIVERSITY OF KANSAS MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2004
资助国家：
美国
起止时间：
2004-04-15 至 2007-03-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Borrelia spirochetes causing relapsing fever (RF) can persist in an infected host by antigenic variation of Vsps and Vlps, two families of variable, immunodominant and thus serotype-defining surface lipoproteins. Vsps and Vlps induce a T-independent neutralizing IgM response, which leads to complement-independent elimination of that specific serotype. Yet, these antibodies do not protect from subsequent spirochetemia of other serotypes. Highlighting an additional evasion strategy, one of two Vsps with different binding affinities to glycosaminoglycans (GAGs) has been implicated in targeting RF Borrelia to the central nervous system, an immunopriviledged site. The overall objective of this proposal is to gain an in-depth understanding of these pathogenic processes by defining the structural and functional basis of Vsp- and VIp-mediated immune evasion and tissue tropism. Their demonstrated overlapping role in both mechanisms lead us to initially focus on the Vsps. Our preliminary data indicate that Vsps share a conserved dimeric and alpha-helical structural fold, with hypervariable loops connecting the alpha helices. We hypothesize that these variable and membrane-distal loops (i) form the Vsp-specific antibody epitopes, and (ii) also confer the surface properties involved in tissue localization. To significantly facilitate our studies, we have developed a novel surface display system, which allows us to stably express and present functional Vsps and Vlps on the surface of the Lyme disease (LD) spirochete Borrelia burgdorferi. We will now apply this system to test our hypothesis and have formulated two major specific aims: 1. to define the neutralizing antibody epitopes of Vsp proteins: Based on the three-dimensional structure of two Vsps and using specific IgG and newly generated IgM monoclonal antibodies, we will map antibody epitopes by analyzing Vsp escape mutants and antibody interactions with Vsp chimeras and point mutants. 2. to define the Vsp domains interacting with GAGs: Chimeras and point mutants of two Vsps will be examined for binding to purified GAGs, glial and endothelial cells as well as for neurotropic characteristics. These studies will significantly increase our understanding of the pathogenesis of Borrelia infections, and shed more light on the mechanisms of antigenic variation and immune evasion of microbes in general. Furthermore, they will yield important clues for the design of future intervention strategies.

描述（由申请人提供）：导致回归热（RF）的疏螺旋体螺旋体可以通过 Vsps 和 Vlps 的抗原变异在感染宿主中持续存在，Vsps 和 Vlps 是两个可变的、免疫显性的、因此定义血清型的表面脂蛋白家族。 Vsps 和 Vlps 诱导 T 独立的中和 IgM 反应，从而导致该特定血清型的补体独立消除。然而，这些抗体不能预防随后的其他血清型的螺旋体血症。突出显示了另一种逃避策略，与糖胺聚糖 (GAG) 具有不同结合亲和力的两个 Vsp 之一已涉及将 RF 伯氏疏螺旋体靶向中枢神经系统（一个免疫豁免位点）。该提案的总体目标是通过定义 Vsp 和 VIp 介导的免疫逃避和组织向性的结构和功能基础，深入了解这些致病过程。它们在两种机制中表现出的重叠作用使我们最初关注 Vsps。我们的初步数据表明，Vsps 具有保守的二聚体和 α 螺旋结构折叠，其中高变环连接 α 螺旋。我们假设这些可变环和膜远端环（i）形成Vsp特异性抗体表位，并且（ii）还赋予涉及组织定位的表面特性。为了显着促进我们的研究，我们开发了一种新型表面展示系统，该系统使我们能够在莱姆病 (LD) 螺旋体伯氏疏螺旋体的表面稳定表达和呈现功能性 Vsps 和 Vlps。我们现在将应用该系统来检验我们的假设，并制定了两个主要的具体目标： 1. 定义Vsp蛋白的中和抗体表位：基于两个Vsp的三维结构，使用特异性IgG和新生成的IgM单克隆抗体，我们将通过分析Vsp逃逸突变体和抗体与Vsp嵌合体的相互作用来绘制抗体表位点突变体。 2. 定义与 GAG 相互作用的 Vsp 结构域：将检查两个 Vsp 的嵌合体和点突变体与纯化的 GAG、神经胶质细胞和内皮细胞的结合以及亲神经特性。这些研究将显着增加我们对疏螺旋体感染发病机制的了解，并进一步阐明微生物的抗原变异和免疫逃避的机制。此外，它们将为未来干预策略的设计提供重要线索。