Background: Increased inflammation is a hallmark of COVID-19, with pulmonary and systemic inflammation identified in multiple cohorts of patients. Definitive cellular and molecular pathways driving severe forms of this disease remain uncertain. Neutrophils, the most numerous leukocytes in blood circulation, can contribute to immunopathology in infections, inflammatory diseases and acute respiratory distress syndrome (ARDS), a primary cause of morbidity and mortality in COVID-19. Changes in multiple neutrophil functions and circulating cytokine levels over time during COVID-19 may help define disease severity and guide care and decision making. Methods: Blood was obtained serially from critically ill COVID-19 patients for 11 days. Neutrophil oxidative burst, neutrophil extracellular trap formation (NETosis), phagocytosis and cytokine levels were assessed ex vivo. Lung tissue was obtained immediately post-mortem for immunostaining. Results: Elevations in neutrophil-associated cytokines IL-8 and IL-6, and general inflammatory cytokines IP-10, GM-CSF, IL-1b, IL-10 and TNF, were identified in COVID-19 plasma both at the first measurement and at multiple timepoints across hospitalization (p < 0.0001). Neutrophils had exaggerated oxidative burst (p < 0.0001), NETosis (p < 0.0001) and phagocytosis (p < 0.0001) relative to controls. Increased NETosis correlated with both leukocytosis and neutrophilia. Neutrophils and NETs were identified within airways and alveoli in the lung parenchyma of 40% of SARS-CoV-2 infected lungs. While elevations in IL-8 and ANC correlated to COVID-19 disease severity, plasma IL-8 levels alone correlated with death. Conclusions: Circulating neutrophils in COVID-19 exhibit an activated phenotype with increased oxidative burst, NETosis and phagocytosis. Readily accessible and dynamic, plasma IL-8 and circulating neutrophil function may be potential COVID-19 disease biomarkers.

中文翻译：

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重症COVID-19患者外周血中性粒细胞活化表型和NETosis升高

背景：炎症增加是COVID-19的标志，在多个患者群中发现了肺部和全身性炎症。导致该病严重形式的决定性细胞和分子途径仍然不确定。中性粒细胞是血液循环中数量最多的白细胞，可导致感染，炎症性疾病和急性呼吸窘迫综合征（ARDS）的免疫病理变化，这是COVID-19发病和死亡的主要原因。COVID-19期间多种嗜中性粒细胞功能和循环细胞因子水平的变化可能有助于确定疾病的严重程度，并指导护理和决策。方法：连续11天从危重的COVID-19患者中采集血液。中性粒细胞氧化爆发，中性粒细胞胞外陷阱形成（NETosis），体外评估吞噬作用和细胞因子水平。死后立即获得肺组织用于免疫染色。结果：首次测量时，在COVID-19血浆中发现了嗜中性粒细胞相关的细胞因子IL-8和IL-6升高，以及一般的炎性细胞因子IP-10，GM-CSF，IL-1b，IL-10和TNF升高。在整个住院期间的多个时间点（p <0.0001）。相对于对照组，中性粒细胞具有夸张的氧化爆发（p <0.0001），NETosis（p <0.0001）和吞噬作用（p <0.0001）。NETosis升高与白细胞增多和中性粒细胞增多相关。在感染了SARS-CoV-2的40％肺的肺实质中，在气道和肺泡内发现了中性粒细胞和NET。IL-8和ANC升高与COVID-19疾病严重程度相关，而血浆IL-8水平仅与死亡相关。结论：COVID-19中的循环中性粒细胞表现出活化的表型，具有氧化爆发，NETosis和吞噬作用增加。血浆IL-8和循环中的中性粒细胞功能易于获取且动态，可能是潜在的COVID-19疾病生物标志物。