CRASP-mediated Serum Resistance by Borrelia burgdorferi

CRASP 介导的伯氏疏螺旋体的血清耐药性

• 批准号: 8953318
• 负责人: JOHN M LEONG
• 金额: $ 25.29万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2017-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8953318
• 关键词: Antibodies; Bacteremia; Bacteria; Bacterial Antigens; Binding; Biological; Bite; Blood; Blood Circulation; Borrelia burgdorferi; Carbohydrates; Complement; Complement 3 Convertase; Complement 3b; Complement Activation; Complement Factor H; Complex; Cytolysis; Defect; Deposition; Dermatan Sulfate; Detection; Development; Disease model; Down-Regulation; Environment; Event; Fostering; Genes; Host Defense; Immune response; In Vitro; Individual; Infection; Inflammation; Investigation; Joints; Knowledge; Laboratories; Lyme Disease; Mannose Binding Lectin; Mannose-Binding Lectins; Mediating; Membrane Proteins; Modeling; Mus; Mutate; Order Spirochaetales; Pathway interactions; Phenotype; Plasmids; Protein Binding; Proteins; Regulation; Resistance; Role; Serum; Site; Skin; Staging; Surface; System; Systemic disease; Test Result; Testing; Ticks; Tissue Survival; Tissues; Vector-transmitted infectious disease; Work; alternative pathway complement C3 convertase; complement system; decorin; genetic regulatory protein; insight; microbial; mutant; paralogous gene; pathogen; prevent; promoter; protein complex; public health relevance

 DESCRIPTION (provided by applicant): Lyme disease, caused by the spirochete Borrelia burgdorferi, is the most common vector-borne disease in U.S. B. burgdorferi can infect the skin at the site of the tick bite and spread via blood to diverse tissues, indicating that the bacterium can withstand bloodstream defenses. The complement system is a bloodstream defense that is activated via three different pathways. A critical step of the activation of this system is the formation of C3 convertases, C4b2a or C3bBb, which catalyze events resulting in inflammation, opsonization and pathogen lysis. Potential host damage following complement activation necessitates tight regulation by serum complement regulators that bind to complement components and promote their degradation. For example, the complement regulator factor H (FH) and C4BP modulates formation of C3bBb and C4b2a, respectively. We recently showed that B. burgdorferi produces DbpA, a surface protein that promotes tissue colonization by binding to dermatan sulfate and decorin, also fosters bacteremia by binding to C4BP. A B. burgdorferi strain producing DbpA-I156A, a point mutant deficient in C4BP binding, showed a delay in bacteremia and joint colonization. In addition, B. burgdorferi also produces CRASPs (Complement Regulator Acquiring Surface Proteins) that bind to complement regulators. The paralogs CspA, CspZ bind to FH and FH-like protein (FHL), and the paralogs ErpP, ErpC, and ErpA bind to FH and complement factor H-related protein (CFHR). Although several CRASPs have been demonstrated to contribute to serum resistance in vitro, none have been definitely shown to contribute to mammalian infection. Recently, we found that a B. burgdorferi strain harboring an erpA::Tn insertion displayed a defect in tissue colonization at early stages of infection. These results suggest that DbpA and ErpA modulate C4b2a and C3bBb, respectively, to promote bacteremia and tissue colonization. The ability of DbpA and ErpA to inhibit the formation of both classes of C3 convertases may signify a coordinated attack on host bloodstream defenses by B. burgdorferi. To test this hypothesis, the following aims will be pursued. (1) Test the role of FH-binding in bacteremia and colonization. We will test if a targeted, non-polar erpA deletion mutant display defects in FH/CFHR binding, complement activation in vitro, and bacteremia and tissue colonization in the murine model. If the mutant displays defects, we will test if FH binding by ErpA is essential for these functions, and whether other CRASPs can functionally complement the defects. (2). Test if C4BP- and FH-binding by B. burgdorferi provide non-redundant roles to promote bacteremia and colonization. To determine if a dramatic dissemination defect requires loss of both C4BP- and FH-binding activities, we will mutate erpA in the strain background of the B. burgdorferi DbpA-I156A mutant. These double mutant strains will be tested for the severe bacteremia and colonization defect in the murine model.

 描述（由申请人提供）：莱姆病由螺旋体伯氏疏螺旋体引起，是美国最常见的媒介传播疾病。伯氏疏螺旋体可以感染蜱虫叮咬部位的皮肤，并通过血液传播到不同的组织，这表明该细菌 可以抵御血流防御。补体系统是一种血流防御系统，通过三种不同的途径激活。该系统激活的关键步骤是 C3 转化酶、C4b2a 或 C3bBb 的形成，它们催化导致炎症、调理作用和病原体裂解的事件。补体激活后潜在的宿主损伤需要血清补体调节剂的严格调节，这些调节剂与补体成分结合并促进其降解。例如，补体调节因子 H (FH) 和 C4BP 分别调节 C3bBb 和 C4b2a 的形成。我们最近表明，伯氏疏螺旋体产生 DbpA，这是一种表面蛋白，通过与硫酸皮肤素和核心蛋白聚糖结合来促进组织定植，还通过与 C4BP 结合来促进菌血症。产生 DbpA-I156A（一种 C4BP 结合缺陷的点突变体）的伯氏疏螺旋体菌株显示菌血症和关节定植延迟。此外，伯氏疏螺旋体还产生与补体调节因子结合的 CRASP（补体调节因子获取表面蛋白）。旁系同源物 CspA、CspZ 与 FH 和 FH 样蛋白 (FHL) 结合，旁系同源物 ErpP、ErpC 和 ErpA 与 FH 和补体因子 H 相关蛋白 (CFHR) 结合。虽然一些 CRASP 已被证明有助于体外血清抗性，但没有一个明确显示有助于哺乳动物感染。最近，我们发现带有 erpA::Tn 插入的伯氏疏螺旋体菌株在感染早期表现出组织定植缺陷。这些结果表明，DbpA 和 ErpA 分别调节 C4b2a 和 C3bBb，以促进菌血症和组织定植。 DbpA 和 ErpA 抑制两类 C3 转化酶形成的能力可能意味着伯氏疏螺旋体对宿主血流防御的协同攻击。为了检验这一假设，将追求以下目标。 (1)测试FH结合在菌血症和定植中的作用。我们将测试靶向非极性 erpA 缺失突变体是否在 FH/CFHR 结合、体外补体激活以及小鼠模型中的菌血症和组织定植方面表现出缺陷。如果突变体表现出缺陷，我们将测试 ErpA 结合 FH 是否对这些功能至关重要，以及其他 CRASP 是否可以在功能上补充缺陷。 （2）。测试伯氏疏螺旋体的 C4BP 和 FH 结合是否提供非冗余作用以促进菌血症和定植。为了确定显着的传播缺陷是否需要丧失 C4BP 和 FH 结合活性，我们将在伯氏疏螺旋体 DbpA-I156A 突变体的菌株背景中突变 erpA。这些双突变株将在小鼠模型中测试严重菌血症和定植缺陷。