Crosstalk of macrophages and eosinophils in helminth-mediated protection during experimental sepsis

当细菌进入血流时，就会发生败血症。伴随而来的是脓毒症时过度的免疫激活，导致病理改变，最终导致多器官衰竭死亡。该项目的最终目标是确定在不阻碍细菌感染清除的情况下抑制这种过度炎症的机制。我们推测，研究蠕虫感染对脓毒症期间发展的免疫反应的影响将使我们能够确定这种机制。与细菌相反，丝虫物种每毫升血液释放多达数百万条微丝虫(丝虫的后代)，而不会引起炎症。为了避免炎症，蠕虫调节宿主的免疫系统，并诱导抗炎、抑制环境。实验研究表明，蠕虫的免疫调节作用可以预防或改善过敏和自身免疫性疾病。然而，慢性蠕虫感染对脓毒症等急性全身性促炎免疫反应的影响尚不清楚。使用唯一允许慢性丝虫病感染的丝虫病小鼠模型，我们能够证明，慢性感染丝虫病小鼠可以改善I.P.注射大肠杆菌，改善体温过低。慢性感染LS会导致嗜酸性粒细胞增多，诱导抗炎、交替激活的巨噬细胞(AAM)，并减少大肠杆菌介导的促炎免疫反应。去除巨噬细胞、嗜酸性粒细胞和抗炎的转化生长因子β可降低LS介导的保护作用，以对抗大肠杆菌的挑战。这项拨款提案将集中于来自肝、脾和腹膜的LS调节的巨噬细胞以及嗜酸性粒细胞在大肠杆菌挑战中的作用。分析将包括表型和功能特征以及基因表达。转移和耗竭实验将研究AAM和转化生长因子β的作用，并揭示哪些巨噬细胞和嗜酸性粒细胞衍生的介质对保护大肠杆菌至关重要。本文将分析巨噬细胞和嗜酸性粒细胞与中性粒细胞和肥大细胞的相互作用。在脓毒症之后，会出现代偿性抗炎反应综合征(CARS)，并导致T细胞瘫痪，从而增加双重感染的风险。由于LS感染可以有效地调节对大肠杆菌的急性免疫反应，因此有人建议进行实验，以测试慢性LS感染对大肠杆菌攻击后的适应性免疫反应和体内特异性CD8 T细胞裂解的影响。进一步的实验将调查注射已知的免疫调节丝虫抗原是否能预防大肠杆菌败血症和CARS。这些研究的结果可能有助于开发新的治疗方法，在不损害身体清除细菌感染的能力的情况下，抑制脓毒症中发生的过度炎症。

Sepsis occurs when bacteria enter the blood stream. Accompanying, excessive immune activation during sepsis causes pathology and eventual death by multi-organ failure. The ultimate goal of this project is to identify mechanisms to suppress this excess inflammation without impeding clearance of the bacterial infection. We postulate that investigating the effects helminth infections have on the immune response that develops during sepsis will enable us to identify such mechanisms. In contrast to bacteria, filarial helminth species release up to millions of microfilariae (progeny of filaria) per milliliter of blood without inducing inflammation. To avoid inflammation, helminths modulate the hosts immune system and induce an anti-inflammatory, suppressive milieu. Experimental studies showed that immunomodulation by helminths prevent or improve allergies and autoimmune diseases. However, the impact of chronic helminth infections on acute systemic pro-inflammatory immune responses like sepsis is scarcely understood. Using the only mouse model of filariasis that allows chronic filarial infection, we were able to show that chronic infection of mice with the filarial nematode Litomosoides sigmodontis (Ls) improves clearance of i.p. injected E. coli bacteria and ameliorates hypothermia. Chronic infection with Ls results in eosinophilia, induction of anti-inflammatory, alternatively activated macrophages (AAM) and reduces E. coli mediated pro-inflammatory immune responses. Depletion of macrophages, eosinophils and anti-inflammatory TGF beta reduces the Ls mediated protective effect against an E. coli challenge.This grant proposal will focus on the role of Ls-modulated macrophages from liver, spleen, and peritoneum as well as eosinophils during an E. coli challenge. Analyzes will include phenotypic and functional characterization as well as gene expression. Transfer and depletion experiments will investigate the role of AAM and TGF beta and unravel which macrophage and eosinophil derived mediators are crucial for the protection against E. coli. The crosstalk of macrophages and eosinophils with neutrophils and mast cells will be analyzed in this context.Following sepsis, a compensatory anti-inflammatory response syndrome (CARS) develops and results in T-cell paralysis that increases the risk for superinfections. As Ls infection efficiently modulates the acute immune response to E. coli, experiments are proposed to test the impact of chronic Ls infection on the adaptive immune response and specific in vivo CD8 T-cell lysis after an E. coli challenge. Further experiments will investigate whether administration of known immunomodulatory filarial antigens protect against E. coli sepsis and CARS. Results of these studies may lead to insights for the development of novel treatments which suppress the excessive inflammation that occurs in sepsis without compromising the bodys ability to clear bacterial infections.