Bacterium-ECM interactions during infection by the Lyme disease spirochete

莱姆病病原伯氏疏螺旋体引起慢性多系统疾病及其相互作用 与细胞外基质(ECM)的几种成分，如纤维连接蛋白(FN)，蛋白多糖核心蛋白， 和糖胺多聚糖(GAG)，被认为可以促进各种组织的感染。几种伯氏杆菌 可能促进这种结合的分子已经被生化鉴定，包括Gag结合。 蛋白Bgp，核心蛋白DbpA和DbpB，以及纤维连接蛋白结合蛋白BBK32。我们 发现携带BGP插入片段的伯氏杆菌在小鼠中仍然具有感染性，这表明BGP不是 殖民所需的。与此一致的是，伯氏杆菌在适应时更有效地与GAG结合 对宿主环境，但没有明显的BGP诱导，这表明其他粘附素可能 有助于封口。事实上，通过在高通道的表面表达DbpA、DbpB或BBK32， 另外，我们证明了除了它们已知的ECM靶标外，所有未贴壁的伯氏杆菌菌株 其中三种能够促进细菌对唾液的附着。DbpA的Gag结合活性受制于 等位基因变异与BBK32的GAG和FN结合活性明显是可分离的。我们 最近在传染性Burgdorferi菌株中产生了Bgp、dbpA/dbpB和bbk32的靶向突变 背景。为了确定细胞外基质的哪些成分是伯氏杆菌黏附的生理受体， 无论它们的同一性是否随不同的靶组织而异，我们都将产生BBK32的衍生物 失去Fn和/或Gag结合活性，以及失去核心蛋白-和/或Gag-的DbpA和B的衍生物 结合活性。小鼠将感染伯氏杆菌bbk32或dbpA/B突变体，以评估 这些粘附素在感染过程中。如果需要bbk32、dbpA和/或dbpB来殖民一个或多个 组织，这些基因的变体导致GAG、核心蛋白和/或FN结合活性的选择性丧失将 接受测试，看他们是否有能力弥补殖民缺陷。通过发展详细的知识 对莱姆病螺旋体的定植和疾病至关重要的相互作用，这些研究可能 导致新的治疗策略，旨在防止这种重要病原体的殖民。是这样的 研究还可能阐明管理由细菌病原体引起的组织特异性感染的一般原则。

Borrelia burgdorferi, the agent of Lyme disease, causes a chronic multisystemic illness, and its interaction with several components of extracellular matrix (ECM), such as fibronectin (Fn), the proteoglycan decorin, and glycosaminoglycans (GAGs), is thought to promote infection of diverse tissues. Several B. burgdorferi molecules that may promote this binding have been identified biochemically, including the GAG-binding protein Bgp, the decorin binding proteins DbpA and DbpB, and the fibronectin binding protein BBK32. We found that B. burgdorferi harboring an insertion in bgp remained infectious in mice, indicating that Bgp is not required for colonization. Consistent with this, B. burgdorferi binds more efficiently to GAGs upon adaptation to the host environment, but without demonstrable induction of bgp, suggesting that other adhesins may contribute to GAG binding. In fact, by expressing DbpA, DbpB or BBK32 on the surface of a high-passage, otherwise nonadherent B. burgdorferi strain, we demonstrated that in addition to their known ECM targets, all three are capable of promoting bacterial attachment to GAGs. The GAG-binding activity of DbpA is subject to allelic variation, and the GAG- and fibronectin-binding activities of BBK32 are apparently separable. We have recently generated targeted mutations of bgp, dbpA/dbpB and bbk32 in infectious B. burgdorferi strain backgrounds. To identify which components of ECM are physiologic receptors of B. burgdorferi adhesion, and whether their identity varies with different target tissues, we will generate derivatives of BBK32 that have lost Fn- and/or GAG-binding activity, and derivatives of DbpA and B that have lost decorin- and/or GAG- binding activity. Mice will be infected with B. burgdorferi bbk32 or dbpA/B mutants to assess the roles of these adhesins during infection. If bbk32, dbpA, /and/or dbpB are required for colonization of one or more tissues, variants of these genes that result in selective loss of GAG-, decorin- and/or Fn-binding activity will be tested for their ability to complement the colonization defect. By developing detailed knowledge of the interactions that are critical to colonization and disease of the Lyme disease spirochete, these studies may lead to novel therapeutic strategies aimed at preventing colonization by this important pathogen. Such studies may also shed light on general principles that govern tissue-specific infection by bacterial pathogens.