Regulation of Innate Immunity by Coagulation Receptors

项目总结 脓毒症是一种危及生命的全身炎症宿主对微生物感染的反应，它影响超过 仅在美国每年就有70万名患者，目前败血症患者的住院死亡率仍高达 大约25%。目前的治疗方法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。许多候选药物在 临床前动物研究，但未能改善，甚至恶化了临床研究的结果。这引起了人们的关注 普遍关注的是对脓毒症病理的深刻缺乏了解，以及动物缺乏 模拟人类疾病和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 天然突变的人凝血因子V(Fv Leiden)保护作用的观察 在人类以及各种败血症和致死性不孕症的小鼠模型中抗感染死亡 发炎。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)触发分子开关的能力 蛋白酶激活受体2(PAR2)的信号转导。这个开关调节了一种未知的 一群独特的、受感染的先天免疫细胞的免疫调节功能 能够消退炎症，提高存活率。拟议研究的目的是 阐明保护该突变杂合携带者免于死亡的细胞和分子机制 通过脓毒症，并应用这些知识来指导针对这些自然生存的治疗方法 小路。这是通过三个具体目标实现的：(1)描述感染的生物反应-- 诱导由两种不同模式的PAR2信号控制的髓系先天免疫细胞，以及如何 这些反应改变了感染的总体结果。(2)确定自然生存如何 在FV Leiden携带者中工作的机制可以通过治疗性给药在正常小鼠中进行 APC的重组变种，选择性地靶向这些通路，而不会导致出血并发症。(3) 为了确定在小鼠身上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，我们的研究将证明以前未知的凝血受体信号转导机制 塑造对感染的先天免疫反应。这些新的途径可以解释有限的疗效 重组APC在过去的临床试验中，也指导了一种基本的方法，以极大地改善临床 APC或具有APC样活性的新型试剂的治疗效果。

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.