Complement and the Clearance of Staphylococcus aureus

金黄色葡萄球菌的补体和清除

• 批准号: 6729197
• 负责人: KENJI Mason CUNNION
• 金额: $ 11.64万
• 依托单位: EASTERN VIRGINIA MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6729197
• 关键词: Mossbauer spectrometry; Staphylococcus aureus; antibody; antigen antibody reaction; bacteria infection mechanism; bacterial capsules; bacterial disease; bactericidal immunity; complement; complement receptor; electron microscopy; gene expression; genetically modified animals; host organism interaction; human tissue; immunogenetics; immunoregulation; intermolecular interaction; laboratory mouse; neutrophil; opsonin; phagocytosis; protein degradation; protein structure function; serotyping; western blottings

This research will characterize the role of complement proteins in the immune-mediated opsonophagocytosis and killing of pathogenic Staphylococcus aureus. S. aureus is a leading cause of death from infection in hospitals and is increasingly resistant to current antibiotics. For many bacteria adequate opsonization by complement proteins is critical for effectively preventing and fighting infections. Studying complement-mediated opsonization of S. aureus may provide clues to unlock new therapies against S. aureus. Encapsulated (CP+) strains, serotypes 5 and 8, cause 70% of severe S. aureus infections, however their opsonization by complement remains largely unstudied. Our preliminary in vivo and in vitro studies and in vitro studies have investigated three CP+ strains, two heavily- encapsulated strains, and one capsule-negative mutant in terms of lethality in complemented mice, C3 binding kinetics, pathways of complement activation, the nature of C3 fragments deposited and shed, the relationship between growth and C3 binding, and the effect of capsule on C3 binding. The data from these studies suggest that complement is important for surviving bacteremia with clinically relevant S. aureus serotypes. CP+ strains appear to inhibit opsonization by decreasing C3 binding, inhibiting bound C3-fragment recognition by complement receptors, and sh4edding bound C3-fragments. The global hypothesis guiding this research is that the severity of S. aur5eus infection depends on serotype dependent staphylococcal-capsule modulation of complement-mediated opsonization. In light of the preliminary data the following focused hypotheses will be tested: 1) Opsonization by complement is critical in host defense against S. aureus. 2) Capsular polysaccharide and impairs opsonphagocytosis of S. aureus by interfering with normal complement function. 3) S. aureus protects itself by degrading and shedding the major complement opsonins C3b and iC3b. 4) Anti-capsular antibodies improve the complement-mediated opsonophagocytosis and killing of S. aureus. These experiments will be performed using radiolabeled complement components, and antibodies raised against specific complement peptides. Human neutrophils will be incubated with opsonized bacteria and stained with acridine orange to measure phagocytosis and intracellular killing. In vivo experiments will be performed using complement deficient mice. Collaborating laboratories have provided special S. aureus stains and anti-S. aureus antibodies.

这项研究将表征补体蛋白在免疫介导的吞噬细胞和杀死致病金黄色葡萄球菌中的作用。金黄色葡萄球菌是医院感染死亡的主要原因，而且对目前的抗生素越来越耐药。对于许多细菌来说，补体蛋白的充分调理对于有效预防和抗击感染至关重要。研究补体介导的金黄色葡萄球菌的调理作用可能为解锁治疗金黄色葡萄球菌的新疗法提供线索。包膜(CP+)菌株，血清型5和8型，引起70%的严重金黄色葡萄球菌感染，然而它们对补体的调理作用在很大程度上仍未被研究。我们在体内、体外和体外的初步研究，从补体对小鼠的致死性、补体C3结合动力学、补体激活途径、C3片段沉积和脱落的性质、生长与C3结合的关系以及胶囊对C3结合的影响等方面，对三株CP+菌株、两株包膜较厚的菌株和一株包膜阴性突变体进行了研究。这些研究的数据表明，补体对于临床相关的金黄色葡萄球菌血清型的菌血症存活是重要的。CP+菌株似乎通过减少C3结合、抑制补体受体对结合的C3片段的识别以及脱落结合的C3片段来抑制调理作用。指导这项研究的全球假说是，金黄色葡萄球菌感染的严重程度取决于血清型依赖的葡萄球菌胶囊对补体介导的调理作用的调节。根据初步数据，将检验以下重点假设：1)补体的调理作用在宿主对金黄色葡萄球菌的防御中起关键作用。2)衣壳多糖通过干扰金黄色葡萄球菌的正常补体功能而损害金黄色葡萄球菌的吞噬功能。3)金黄色葡萄球菌通过降解和脱落主要补体调色素C3b和iC3b来保护自身。4)抗衣壳抗体可增强补体介导的吞噬细胞功能和对金黄色葡萄球菌的杀灭作用。这些实验将使用放射性标记的补体成分和针对特定补体多肽产生的抗体来进行。人的中性粒细胞将与调理细菌孵育，并用吖啶橙染色来测量吞噬能力和细胞内杀伤力。体内实验将使用补体缺乏的小鼠进行。合作实验室提供了特殊的金黄色葡萄球菌染色和抗S。金黄色抗体。