Hemostatic Factors as Determinants of Bacterial Virulence and Host Defense

描述(申请人提供)：本研究计划的长期目标是了解关键的凝血和纤溶因子在炎性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活体实验环境中实现，我们建议的研究重点是核心止血因子发生特定变化的基因靶向小鼠的先天免疫监测和细菌发病机制。该项目的目标集中在以下特定假设：i)介导纤维蛋白沉积和溶解的宿主因素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素用于颠覆宿主防御，iii)受挑战组织内的白细胞与纤维蛋白的结合是导致实施有效抗菌功能的重要线索，以及iv)止血因素控制白细胞激活事件以及巨噬细胞从炎症部位进入淋巴管。这些假说将通过对缺乏纤维蛋白原或表达突变形式的纤维蛋白原的小鼠的毒力/宿主防御的详细研究来验证，这些突变形式的纤维蛋白原要么缺乏白细胞整合素受体αMbeta2结合基序，要么缺乏血小板整合素受体α(IIb)β3结合基序，或者不能转化为纤维蛋白基质(Aim I)。此外，促凝剂和纤溶因子在建立金黄色葡萄球菌毒力/宿主防御中的作用将通过研究人员对凝血酶原、纤溶酶原和它们各自的微生物衍生激活物：凝固酶和葡萄球菌激活剂的基因变化来确定(目标2和3)。最后，将在金黄色葡萄球菌腹膜炎的背景下确定中性粒细胞和巨噬细胞在纤维蛋白原/凝血酶原依赖的细菌清除中的机械作用(目标3)。拟议的研究将提供关于止血和炎症系统在体内实施有效的抗菌反应时的相互作用的详细了解。此外，这些研究可能阐明以特定止血系统成分为中心的治疗策略，这些成分在治疗危及生命的微生物感染/败血症方面有效。通俗描述：细菌是导致人类痛苦和死亡的最常见原因，它们一致进化出利用凝血因子的手段，显然是作为一种颠覆宿主防御的手段。这项研究的目的是从机制上详细了解宿主止血因子在细菌毒力和炎症反应中的作用，以此作为威胁生命的传染病的新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.