Data_Sheet_1_Excessive Neutrophils and Neutrophil Extracellular Traps in COVID-19.doc

Background: Cases of excessive neutrophil counts in the blood in severe coronavirus disease (COVID-19) patients have drawn significant attention. Neutrophil infiltration was also noted on the pathological findings from autopsies. It is urgent to clarify the pathogenesis of neutrophils leading to severe pneumonia in COVID-19.Methods: A retrospective analysis was performed on 55 COVID-19 patients classified as mild (n = 22), moderate (n = 25), and severe (n = 8) according to the Guidelines released by the National Health Commission of China. Trends relating leukocyte counts and lungs examined by chest CT scan were quantified by Bayesian inference. Transcriptional signatures of host immune cells of four COVID19 patients were analyzed by RNA sequencing of lung specimens and BALF.Results: Neutrophilia occurred in 6 of 8 severe patients at 7–19 days after symptom onset, coinciding with lesion progression. Increasing neutrophil counts paralleled lesion CT values (slope: 0.8 and 0.3–1.2), reflecting neutrophilia-induced lung injury in severe patients. Transcriptome analysis revealed that neutrophil activation was correlated with 17 neutrophil extracellular trap (NET)-associated genes in COVID-19 patients, which was related to innate immunity and interacted with T/NK/B cells, as supported by a protein–protein interaction network analysis.Conclusion: Excessive neutrophils and associated NETs could explain the pathogenesis of lung injury in COVID-19 pneumonia.

背景：在严重冠状病毒疾病（COVID-19）患者中，血液中嗜中性粒细胞计数异常升高的病例引起了广泛关注。尸检病理学检查亦发现嗜中性粒细胞浸润。亟需阐明嗜中性粒细胞导致COVID-19重症肺炎的发病机制。方法：对55例根据中国国家卫生健康委员会发布的指南分为轻症（n = 22）、中度（n = 25）和重症（n = 8）的COVID-19患者进行了回顾性分析。通过贝叶斯推理对与白细胞计数相关的胸部CT扫描肺部检查趋势进行量化。通过肺组织样本和支气管肺泡灌洗液（BALF）的RNA测序分析四位COVID-19患者的宿主免疫细胞转录组特征。结果：在8例重症患者中，有6例在症状出现后7-19天内出现嗜中性粒细胞增多，与病变进展一致。嗜中性粒细胞计数增加与病变CT值平行（斜率：0.8和0.3-1.2），反映了重症患者中嗜中性粒细胞诱导的肺损伤。转录组分析显示，嗜中性粒细胞激活与COVID-19患者中17个与嗜中性粒细胞胞外陷阱（NET）相关的基因相关，这与先天免疫有关，并通过蛋白质-蛋白质相互作用网络分析证实与T/NK/B细胞相互作用。结论：过多的嗜中性粒细胞及其相关的NETs可以解释COVID-19肺炎肺损伤的发病机制。