Borrelia burgdorferi-glycosaminoglycan interactions and Lyme disease pathogenesis

描述(申请人提供)：莱姆病是美国最流行的扁虱传播疾病，影响心脏、关节、皮肤、肌肉骨骼和神经系统。最近，美国报告的病例增加到每年2万例。病原体伯氏疏螺旋体经常在免疫反应强烈的情况下持续存在，并可导致丧失能力的慢性疾病表现，如关节炎或神经疏螺旋体病。我的长期目标是描述宿主与细菌之间的相互作用，这对于细菌感染和莱姆病的发生至关重要。许多微生物对各种组织的定植需要附着在细胞或细胞外基质(ECM)上。糖胺多聚糖(GAG)是蛋白多糖的碳水化合物单位，是哺乳动物细胞上普遍表达的细胞外基质成分。我们的广泛研究表明，缝隙结合是伯氏杆菌的主要黏附机制。事实上，我们已经证明伯氏杆菌产生几种与Gag结合的粘附素，包括：(I)DbpA和DbpB，(Ii)疏螺旋体Gag结合蛋白(BGP)，和(Iii)BBK32。与粘附素的多样性一致的是，缺少一种或两种已知莱姆螺旋体粘附素的突变体仍具有一定程度的传染性。我们的伯氏杆菌Bgp突变体和bbk32突变体在具有免疫能力的小鼠中仍然具有感染性。其中至少前三个显示出殖民缺陷。骨钙素还具有5‘-甲硫腺苷/S-腺苷同型半胱氨酸核苷酶活性。然而，目前尚不清楚BGP突变体的定植缺陷是否与其Gag结合活性、其核苷酶活性或两者都有关。为了确定BGP突变体的定植缺陷是否与其Gag结合、其酶活性或两者都有关，以及BGP是否显示出与其他Gag结合粘附素的部分功能冗余，将追求以下目标。(1)。描述BGP的GAG结合和MTA/SAH核苷酶活性。(2)。确定感染期间定植所需的BGP活性。(3)。评估BGP与其他GAG结合粘附素在定植过程中的功能冗余。意义重大。我们首先认识到BGP是一种多功能表面蛋白，观察了它在小鼠感染过程中在组织定植中的作用，并确定它是新药的靶点。这项研究将从基因上描述BGP的两种活性，以评估感染期间是否需要其中一种或两种活性。我们还将确定BGP和DbpA-DbpB产生的缺陷是相加的，还是各自对伯氏杆菌的组织特异性定植有贡献。了解BGP、DbpA和DbpB的螺旋体-Gag相互作用，对莱姆病发病机制的影响，以及BGP作为代谢酶的作用，有助于设计更好的诊断试验，并有助于开发新的治疗策略，特别是对莱姆病的晚期。

DESCRIPTION (provided by applicant): Lyme disease is the most prevalent tick-borne disease in the USA and affects the heart, joints, skin, musculoskeletal and nervous systems. Recently, the reported cases in the USA have increased to e20,000 per year. The causative agent, Borrelia burgdorferi, often persists in the face of a strong immune response and can result in incapacitating chronic disease manifestations, such as arthritis or neuroborreliosis. My long-term goal is to describe the host-bacterial interactions essential for establishment of the bacterial infection and consequently Lyme disease. Colonization of various tissues by many microbial pathogens requires attachment to cells or extracellular matrix (ECM). Glycosaminoglycans (GAGs) are carbohydrate units of proteoglycans, which are ubiquitously expressed ECM components on mammalian cells. Our extensive studies show that GAG-binding is a major adherence mechanism of B. burgdorferi. Indeed, we have shown that B. burgdorferi produces several GAG- binding adhesins, including, (i) DbpA and DbpB, (ii) Borrelia GAG-binding Protein (Bgp), and (iii) BBK32. Consistent with the multiplicity of GAG-binding adhesins, mutants lacking one or two documented adhesins of Lyme spirochetes retain some degree of infectivity. B. burgdorferi dbpA-dbpB double deletion mutants, generated in a variety of strain backgrounds, our B. burgdorferi bgp mutants, and bbk32 mutants remain infectious in immunocompetent mice. At least first three of these exhibit colonization defect. Bgp also exhibits 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase activity. However, it is not known if the colonization defect of the bgp mutant is related to its GAG-binding activity, its nucleosidase activity, or both. To determine if the defect in colonization by a bgp mutant is related to its GAG-binding, its enzymatic activity, or both, and whether Bgp displays partial functional redundancy with other GAG-binding adhesins, the following aims will be pursued. (1). Delineate the GAG-binding and MTA/SAH nucleosidase activities of Bgp. (2). Define the activity of Bgp required for colonization during infection. (3). Assess the functional redundancy of Bgp with other GAG-binding adhesins during colonization. Significance. We first recognized Bgp as a multifunctional surface protein, observed its role in tissue colonization during mouse infection, and determined it to be a target of novel drugs. This study will genetically delineate two activities of Bgp to assess if one or both activities are required during infection. We will also determine if defect in Bgp and DbpA-DbpB production is additive or each contribute to the tissue- specific colonization by B. burgdorferi. Such an understanding of the spirochete-GAG interactions involving Bgp, DbpA and DbpB, on Lyme pathogenesis and of the role of Bgp as a metabolic enzyme could help design better diagnostic tests and facilitate the development of novel treatment strategies, especially for the later stages of Lyme disease.