Complement and the Clearance of Staphylococcus aureus

本研究将描述补体蛋白在免疫介导的调理吞噬和杀伤致病性金黄色葡萄球菌中的作用。金黄色葡萄球菌是医院感染导致死亡的主要原因，并且对现有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对于有效预防和对抗感染至关重要。研究补体介导的金黄色葡萄球菌的调理可能为开发新的金黄色葡萄球菌治疗方法提供线索。封装（CP+）菌株，血清型5和8，导致70%的严重金黄色葡萄球菌感染，但补体对它们的调节作用在很大程度上尚未研究。我们的初步体内、体外和体外研究从补体小鼠的致死率、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结合的影响等方面研究了3种CP+菌株、2种重包膜菌株和1种包膜阴性突变体。这些研究的数据表明，补体对于临床相关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C3片段的识别和切割结合C3片段来抑制opsonization。指导本研究的总体假设是，金黄色葡萄球菌感染的严重程度取决于补体介导的补体介导的葡萄球菌胶囊调节的血清型依赖性。根据初步数据，以下假设将被验证：1)补体的调理在宿主防御金黄色葡萄球菌中至关重要。2)荚膜多糖通过干扰正常补体功能损害金黄色葡萄球菌的拮抗吞噬功能。3)金黄色葡萄球菌通过降解和脱落主要补体调理素C3b和iC3b来保护自己。4)抗荚膜抗体提高补体介导的调理吞噬作用和金黄色葡萄球菌的杀伤能力。这些实验将使用放射性标记的补体成分和针对特定补体肽的抗体进行。将人中性粒细胞与调理菌一起培养，用吖啶橙染色以测定吞噬和细胞内杀伤。体内实验将在补体缺陷小鼠中进行。合作实验室提供了特殊的金黄色葡萄球菌染色剂和抗金黄色葡萄球菌染色剂。球菌抗体。

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.