Complement and the Clearance of Staphylococcus aureus

金黄色葡萄球菌的补体和清除

• 批准号: 6653926
• 负责人: KENJI Mason CUNNION
• 金额: $ 10.56万
• 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/6653926
• 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.

本研究将描述补体蛋白在免疫介导的调理吞噬和杀死致病性金黄色葡萄球菌中的作用。S.金黄色葡萄球菌是医院感染死亡的主要原因，并且对当前的抗生素的耐药性越来越强。对于许多细菌来说，补体蛋白的充分调理作用对于有效预防和对抗感染至关重要。研究补体介导的S.金黄色葡萄球菌可能提供线索，以解锁新的治疗方法对S。金黄色。包封（CP+）菌株，血清型5和8，导致70%的严重的S。金黄色葡萄球菌感染，然而，它们通过补体的调理作用仍然在很大程度上未被研究。我们的初步体内和体外研究以及体外研究已经研究了三种CP+菌株、两种重包囊菌株和一种包囊阴性突变体在补体小鼠中的致死率、C3结合动力学、补体激活途径、沉积和脱落的C3片段的性质、生长与C3结合之间的关系以及包囊对C3结合的影响。这些研究的数据表明，补体对于临床相关的链球菌菌血症的存活是重要的。金黄色葡萄球菌血清型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。指导这项研究的总体假设是，S。金黄色葡萄球菌感染依赖于补体介导的调理作用的血清型依赖性葡萄球菌荚膜调节。根据初步数据，将检验以下重点假设：1）补体调理作用在宿主防御S。金黄色。2)荚膜多糖和损害调理吞噬S。金黄色葡萄球菌通过干扰正常的补体功能。3)S.金黄色葡萄球菌通过降解和脱落主要补体调理素C3 b和iC 3b来保护自身。4)抗荚膜抗体改善补体介导的调理吞噬作用和对S.金黄色。这些实验将使用放射性标记的补体成分和针对特异性补体肽产生的抗体进行。将人中性粒细胞与调理细菌一起孵育，并用吖啶橙子染色以测量吞噬作用和细胞内杀伤。将使用补体缺陷小鼠进行体内实验。合作实验室提供了特殊的S。金黄色葡萄球菌和抗-S.金黄色葡萄球菌抗体