Role of Complement Activation in Severe COVID-19

项目摘要/摘要：对特别利益通知的回应：基本补充 免疫学(Cibi)，我们建议研究补体在重症肝炎发病机制中的致病作用。 新冠肺炎。补体系统通过三种途径之一激活--经典途径、替代途径和 甘露糖结合凝集素(MBL)--聚集在C3裂解处，导致C3和C5的形成 转化酶，并以膜攻击复合体(MAC)的组装结束。Mac是一种溶细胞剂 在病理条件下可以插入宿主细胞膜的大分子孔。广泛性 从其他人和我们那里获得的证据表明，补体(C)系统，特别是MAC，可以 参与介导内皮细胞损伤，激活凝血途径和血小板，并导致 多器官损害导致严重新冠肺炎。然而，C和MAC在重症中的致病作用 新冠肺炎还没有被实验性地调查过。拟议的研究将利用我们新开发的 最先进的工具来阻断或修饰C激活产物以研究C在内皮细胞中的作用 严重新冠肺炎的损害、血小板活化和血栓形成，包括治疗性 范例。为了满足我们的需求，我们建立了一种严重COVID的动物模型，并对其进行了表征- 19用SARS-CoV-2感染的K18-hACE2小鼠。小鼠出现急性呼吸窘迫综合征 (ARDS)，进行性体重减轻，以及与严重间质炎症相关的7天死亡率， 肺部血管周围炎症、血小板活化和血栓形成。我们还观察到(I)内皮细胞 (EC)肺泡间隔功能障碍；(Ii)血管通透性增加与广泛的 激活免疫细胞(如肺巨噬细胞)；以及(Iii)增加C3和MAC在 肺血管系统。此外，单细胞RNAseq显示C活化和凝血在肺 严重的新冠肺炎模式。这些结果促使我们假设C一般，而MAC在 特别是，对EC损伤、血小板激活和血栓形成有显著促进作用 严重的新冠肺炎病例。目标1将调查C激活和MAC形成的抑制是否会 减少SARS-CoV-2感染的K18小鼠内皮细胞损伤及血小板和凝血通路的激活。目标2 将检验这样一种假设，即限制MAC形成将保护EC免受EC损伤和激活 髓系细胞，导致感染SARS-CoV-2的K18小鼠的血小板和凝血活性降低。 目的3将在一个临床相关的范例中研究C在SARS-CoV-2感染发病机制中的作用 评估部位靶向C抑制作为新冠肺炎的治疗方法。帮助我们更好地理解C激活的作用 而MAC在重症新冠肺炎的发病机制中，开辟了防治新冠肺炎的新途径，促进了 涉及调节C系统的新治疗策略的开发。

Project summary/Abstract: In response to Notice of Special Interest (NOSI): Complement in Basic Immunology (CIBI), we propose to examine the causative effect of complements in the pathogenesis of severe COVID-19. The complement system is activated via one of three pathways—classical, alternative, and mannose-binding lectin (MBL)—which converge at C3 cleavage, leading to the formation of C3 and C5 convertases and concluding with assembly of the membrane attack complex (MAC). MAC is a cytolytic macromolecular pore that can insert into host cell membranes under pathological conditions. Extensive evidence obtained from others and us indicates that the complement (C) system, in particular MAC, may participate in mediating endothelial damage, activating the coagulation pathway and platelets, and causing multiple organ damage leading to severe COVID-19. However, the causative roles of C and MAC in severe COVID-19 have not been experimentally investigated. The proposed studies will utilize our newly developed state-of-the-art tools to block or modify the C activation products to investigate the role of C in endothelial cell damage, platelet activation, and thrombosis formation seen in severe COVID-19, including therapeutic paradigms. To address our needs, we have established and characterized an animal model of severe COVID- 19 using SARS-CoV-2-infected K18-hACE2 mice. The mice develop acute respiratory distress syndrome (ARDS), progressive weight loss, and mortality at 7 days that is associated with severe interstitial inflammation, perivascular inflammation, platelet activation, and thrombosis in the lungs. We also observe (i) endothelial cell (EC) dysfunction of the alveolar septa; (ii) increased vascular permeability associated with the extensive activation of immune cells (e.g., lung macrophage cells); and (iii) increased C3 and MAC deposition in pulmonary vasculature. In addition, single-cell RNAseq shows C activation and coagulation in the lungs of this severe COVID-19 model. These results have prompted us to hypothesize that the C in general, and MAC in particular, significantly contribute to the EC damage, platelet activation, and thrombosis formation seen in severe cases of COVID-19. Aim 1 will investigate whether the inhibition of C activation and MAC formation will reduce EC damage and platelet and coagulation pathway activation in SARS-CoV-2-infected K18 mice. Aim 2 will test the hypothesis that the restriction of MAC formation will protect against EC damage and activation of the myeloid cells, leading to reduced platelet and coagulation activation in SARS-CoV-2-infected K18 mice. Aim 3 will investigate the role of C in the pathogenesis of SAR-CoV-2 infection in a clinically relevant paradigm and evaluate site-targeted C inhibition as a treatment for COVID-19. help us better understand the role of C activation and the MAC in pathogenesis of severe COVID-19, open a new avenue to prevent and treat COVID-19, and foster the development of new therapeutic strategies involving modulation of the C system.