Regulation of Innate Immunity by Coagulation Receptors

项目摘要 脓毒症是一种危及生命的全身性炎症宿主对微生物感染的反应， 仅在美国，每年就有70万例患者，目前脓毒症患者的住院死亡率仍高达 大约25%。目前的治疗仅限于用抗生素控制感染和加强支持性护理 以维持器官功能，迫切需要新的治疗方法。许多候选药物显示出希望， 临床前动物研究，但未能改善，甚至恶化了临床研究的结果。这引发 普遍关注严重缺乏对脓毒症病理学的理解，以及动物实验的不足， 模拟人类疾病并预测临床疗效的研究。 该项目采取了一种完全不同的方法来解决这些问题，并基于 观察到人凝血因子V（fV Leiden）中天然存在的突变可保护 针对人类感染死亡，以及各种败血症和致死性不育的小鼠模型， 炎症我们的初步研究表明，fV莱顿携带者的自然生存优势是 由内源性活化蛋白C（aPC）以下述模式触发分子开关的能力介导： 蛋白酶激活受体2（PAR 2）信号转导。这种开关调节着一种未知的 一个独特的方式，感染引起的先天免疫细胞群体的免疫调节功能， 能够解决炎症并提高生存率。拟议研究的目的是 阐明保护这种突变的杂合子携带者免于死亡的细胞和分子机制 并应用这些知识来指导针对这些自然生存的治疗方法， 途径。这是在三个具体目标完成：（1）描绘感染的生物反应- 引发的骨髓先天免疫细胞，由两种交替模式的PAR 2信号传导控制，以及如何 这些反应改变了感染的总体结果。(2)为了确定自然生存 在正常小鼠中，通过治疗性给予 选择性靶向这些通路而不引起出血并发症的aPC的重组变体。（三） 为了确定在小鼠中发现的新的分子和细胞免疫机制是否也是 与人类宿主对感染的反应有关。 因此，我们的研究将记录以前未知的机制，凝血受体信号 形成了对感染的先天免疫反应。这些新途径可以解释 重组aPC在过去的临床试验中，也指导了一个合理的方法，大大提高了临床 使用aPC或具有aPC样活性的新型试剂的治疗的功效。

PROJECT SUMMARY Sepsis is a life-threatening systemic inflammatory host response to microbial infection that affects in excess of 700,000 patients annually in the US alone, with current in-hospital mortality of septic patients still reaching about 25%. Current treatments are limited to control of infection with antibiotics and intensive supportive care to sustain organ function, and new therapies are urgently needed. Many candidate drugs showed promise in preclinical animal studies, but failed to improve, or even worsened outcomes in clinical studies. This has raised general concerns about a profound lack of understanding of sepsis pathology, and the inadequacy of animal studies to mimic human disease and predict clinical efficacy. This project takes a radically different approach to address these concerns and is based on the seminal observation that a naturally occurring mutation in human blood coagulation factor V (fV Leiden) protects against death from infection in humans, as well as in various mouse models of sepsis and lethal sterile inflammation. Our preliminary studies indicate that the natural survival advantage of fV Leiden carriers is mediated by the ability of endogenous activated protein C (aPC) to trigger a molecular switch in the mode of signal transduction by protease-activated receptor 2 (PAR2). This switch modulates in an as yet unknown manner the immune-regulatory function of a distinct, infection-elicited population of innate immune cells to enable the resolution of inflammation and improve survival. The objective of the proposed studies is to delineate the cellular and molecular mechanisms that protect heterozygous carriers of this mutation from death by sepsis, and apply this knowledge to instruct therapeutic approaches targeting these natural survival pathways. This is accomplished in three specific aims: (1) To delineate the biological responses of infection- elicited myeloid innate immune cells that are controlled by two alternate modes of PAR2 signaling, and how these responses modify the overall outcome of infection. (2) To determine how the natural survival mechanisms operating in fV Leiden carriers can be engaged in normal mice by therapeutic administration of recombinant variants of aPC that selectively target these pathways without causing bleeding complications. (3) To determine whether the novel molecular and cellular immune mechanisms discovered in mice also are relevant to the human host response to infection. Our studies will thereby document previously unknown mechanisms by which coagulation receptor signaling shapes the innate immune response to infection. These novel pathways can explain the limited efficacy of recombinant aPC in past clinical trials, and also instruct a rationale approach for greatly improving the clinical efficacy of therapies with aPC or novel reagents with aPC-like activity.