Hemostatic Factors as Determinants of Bacterial Virulence and Host Defense

描述（由申请人提供）：本研究项目的长期目标是了解关键凝血和纤溶因子在炎症宿主防御和细菌毒力中的作用。由于对这些复杂过程的严格理解只能在体内实验环境中实现，因此我们提出的研究重点是在核心止血因子发生特定改变的基因靶向小鼠中进行先天免疫监视和细菌发病机制。该项目的目标集中在以下具体假设上：i）介导纤维蛋白沉积和溶解的宿主因子是体内炎症反应的重要决定因素，ii）已知结合/激活宿主凝血酶原、纤维蛋白原和纤溶酶原的细菌因子用于破坏宿主防御，iii）白细胞与受攻击组织内纤维蛋白的接合是导致有效抗微生物功能实现的“靶识别”的重要线索，和iv）止血因子控制白细胞活化事件以及巨噬细胞从炎症部位进入止血系统。这些假设将通过对S.在缺乏纤维蛋白（原）或表达纤维蛋白原的突变形式的小鼠中，缺乏白细胞整联蛋白受体α M β 2结合基序，缺乏血小板整联蛋白受体α（IIb）β 3结合基序，或不能转化为纤维蛋白基质（Aim I）的金黄色葡萄球菌毒力/宿主防御。进一步探讨了促凝血因子和纤溶因子在S.金黄色葡萄球菌毒力/宿主防御将通过凝血酶原、纤溶酶原和它们各自的微生物来源的活化剂：凝固酶和葡激酶中的促凝剂施加的遗传变化来确定（目的2和3）。最后，中性粒细胞和巨噬细胞在纤维蛋白原/凝血酶原依赖性细菌清除中的机制作用将在S.金黄色葡萄球菌性腹膜炎（Aim 3）。拟定的研究将详细了解在体内实施有效抗菌反应时止血和炎症系统之间的相互作用。此外，这些研究可以阐明以特定止血系统成分为中心的治疗策略，这些成分可有效治疗危及生命的微生物感染/脓毒症。铺设说明：细菌是人类痛苦和死亡的最常见原因，它们一致地进化出了与凝血因子结合的方式，显然是作为破坏宿主防御的一种手段。本研究的目标是对宿主止血因子在细菌毒力和炎症反应中的作用进行详细的机制了解，作为针对危及生命的传染病的新型治疗干预措施的一步。

DESCRIPTION (provided by applicant): The long-term objective of this research program is to understand the roles of key coagulation and fibrinolytic factors in inflammatory host defense and bacterial virulence. Since a rigorous understanding of these complex processes can only be achieved in an in vivo experimental setting, our proposed studies focus on innate immune surveillance and bacterial pathogenesis in gene-targeted mice with specific alterations in core hemostatic factors. The aims of this project center on the following specific hypotheses: i) host factors mediating fibrin deposition and dissolution are important determinants of the inflammatory response in vivo, ii) bacterial factors known to bind/activate host prothrombin, fibrinogen and plasminogen serve to subvert host defense, iii) leukocyte engagement of fibrin within challenged tissues is an important cue in "target recognition" leading to the implementation of effective antimicrobial functions, and iv) hemostatic factors control leukocyte activation events as well as macrophage egress from inflammatory sites into lymphatics. These hypotheses will be tested through detailed studies of S. aureus virulence/host defense in mice lacking fibrin(ogen) or expressing mutant forms of fibrinogen that either lack the leukocyte integrin receptor alphaMbeta2 binding motif, lack platelet integrin receptor alpha(IIb)beta3 binding motif, or cannot be converted to a fibrin matrix (Aim I). Further, the role of procoagulant and fibrinolytic factors in establishing S. aureus virulence/host defense will be determined through investigator-imposed genetic changes in prothrombin, plasminogen and their respective microbial-derived activators: coagulase and staphylokinase (Aim 2 and 3). Finally, the mechanistic role of neutrophils and macrophages in the fibrinogen/prothrombin-dependent bacterial clearance will be established in the context of S. aureus peritonitis (Aim 3). The proposed studies will provide a detailed understanding of the cross-talk between the hemostatic and inflammatory systems in the implementation of effective antimicrobial response in vivo. Further, these studies may illuminate therapeutic strategies centering on specific hemostatic system components that are effective in the treatment of life-threatening microbial infection/sepsis. Lay Description: The bacterial species that are the most common causes of human suffering and death have uniformly evolved the means to engage coagulation factors, apparently as a means of subverting host defense. The goal of this research is to develop a detailed mechanistic understanding of the role of host hemostatic factors in bacterial virulence and the inflammatory response as a step toward novel therapeutic interventions for life-threatening infectious disease.