PDF(Pubmed)
Abstract：
COVID-associated coagulopathy seemly plays a key role in post-acute sequelae of SARS- CoV-2 infection. However, the underlying pathophysiological mechanisms are poorly understood, largely due to the lack of suitable animal models that recapitulate key clinical and pathological symptoms. Here, we fully characterized AC70 line of human ACE2 transgenic (AC70 hACE2 Tg) mice for SARS-CoV-2 infection. We noted that this model is highly permissive to SARS-CoV-2 with values of 50% lethal dose and infectious dose as ~ 3 and ~ 0.5 TCID50 of SARS-CoV-2, respectively. Mice infected with 105 TCID50 of SARS-CoV-2 rapidly succumbed to infection with 100% mortality within 5 days. Lung and brain were the prime tissues harboring high viral titers, accompanied by histopathology. However, viral RNA and inflammatory mediators could be detectable in other organs, suggesting the nature of a systemic infection. Lethal challenge of AC70 hACE2 Tg mice caused acute onset of leukopenia, lymphopenia, along with an increased neutrophil-to-lymphocyte ratio (NLR). Importantly, infected animals recapitulated key features of COVID-19-associated coagulopathy. SARS-CoV-2 could induce the release of circulating neutrophil extracellular traps (NETs), along with activated platelet/endothelium marker. Immunohistochemical staining with anti-platelet factor-4 (PF4) antibody revealed profound platelet aggregates especially within blocked veins of the lungs. We showed that acute SARS-CoV-2 infection triggered a hypercoagulable state coexisting with ill-regulated fibrinolysis. Finally, we highlighted the potential role of Annexin A2 (ANXA2) in fibrinolytic failure. ANXA2 is a calcium-dependent phospholipid-binding protein that forms a heterotertrameric complexes localized at the extracellular membranes with two S100A10 small molecules acting as a co-receptor for tissue-plasminogen activator (t-PA), tightly involved in cell surface fibrinolysis. Thus, our results revealing elevated IgG type anti-ANXA2 antibody production, downregulated de novo ANXA2/S100A10 synthesis, and reduced ANXA2/S100A10 association in infected mice, this protein might serve as druggable targets for development of antithrombotic and/or anti-fibrinolytic agents to attenuate pathogenesis of COVID-19.
摘要：
COVID相关性凝血病似乎在SARS-CoV-2感染的急性后遗症中起关键作用。然而,潜在的病理生理机制知之甚少，主要是由于缺乏能够概括关键临床和病理症状的合适动物模型。这里,我们充分表征了SARS-CoV-2感染的人ACE2转基因（AC70hACE2Tg）小鼠的AC70系。我们注意到，该模型高度允许SARS-CoV-2，其50％致死剂量和感染剂量的值分别为SARS-CoV-2的〜3和〜0.5TCID50。感染了105TCID50的SARS-CoV-2的小鼠在5天内以100%的死亡率迅速死于感染。肺和脑是病毒滴度高的主要组织，伴随着组织病理学。然而,病毒RNA和炎症介质可以在其他器官中检测到，提示了全身性感染的性质.AC70hACE2Tg小鼠的致死性攻击引起白细胞减少症的急性发作，淋巴细胞减少,中性粒细胞与淋巴细胞比率（NLR）增加。重要的是,受感染的动物概述了COVID-19相关凝血病的关键特征。SARS-CoV-2可诱导循环中性粒细胞胞外捕获网(NETs)的释放,以及活化的血小板/内皮标志物。用抗血小板因子4（PF4）抗体进行的免疫组织化学染色显示出明显的血小板聚集物，尤其是在肺阻塞的静脉内。我们表明，急性SARS-CoV-2感染引发了高凝状态，并伴有异常调节的纤维蛋白溶解。最后,我们强调了膜联蛋白A2(ANXA2)在纤溶衰竭中的潜在作用.ANXA2是一种钙依赖性磷脂结合蛋白，与两个S100A10小分子形成位于细胞外膜的异四聚体复合物，作为组织纤溶酶原激活剂（t-PA）的共受体。紧密参与细胞表面纤维蛋白溶解。因此，我们的结果显示IgG型抗ANXA2抗体产生升高，从头下调ANXA2/S100A10合成，并减少感染小鼠的ANXA2/S100A10关联，该蛋白可能作为开发抗血栓和/或抗纤溶药物以减轻COVID-19发病机制的药物靶标.
