Circulating Markers of Neutrophil Extracellular Traps Are of Prognostic Value in Patients With COVID-19

Abstract

Objective: The full spectrum of coronavirus disease 2019 (COVID-19) infection ranges from asymptomatic to acute respiratory distress syndrome, characterized by hyperinflammation and thrombotic microangiopathy. The pathogenic mechanisms are poorly understood, but emerging evidence suggest that excessive neutrophil extracellular trap (NET) formation plays a key role in COVID-19 disease progression. Here, we evaluate if circulating markers of NETs are associated with COVID-19 disease severity and clinical outcome, as well as to markers of inflammation and in vivo coagulation and fibrinolysis. Approach and Results: One hundred six patients with COVID-19 with moderate to severe disease were enrolled shortly after hospital admission and followed for 4 months. Acute and convalescent plasma samples as well as plasma samples from 30 healthy individuals were assessed for markers of NET formation: citrullinated histone H3, cell-free DNA, NE (neutrophil elastase). We found that all plasma levels of NET markers were elevated in patients with COVID-19 relative to healthy controls, that they were associated with respiratory support requirement and short-term mortality, and declined to those found in healthy individuals 4 months post-infection. The levels of the NET markers also correlated with white blood cells, neutrophils, inflammatory cytokines, and C-reactive protein, as well as to markers of in vivo coagulation, fibrinolysis, and endothelial damage.

Conclusions: Our findings suggest a role of NETs in COVID-19 disease progression, implicating their contribution to an immunothrombotic state. Further, we observed an association between circulating markers of NET formation and clinical outcome, demonstrating a potential role of NET markers in clinical decision-making, as well as for NETs as targets for novel therapeutic interventions in COVID-19.

Keywords: Sars-Cov2; cytokines; extracellular traps; fibrinolysis; histone; immunothrombosis; thrombosis.

Figure 1.

Coronavirus disease 2019 (COVID-19) disease causes alteration in the circulating markers of neutrophil extracellular trap formation. A, Plasma levels of nucleosomal citrullinated histone H3 (H3Cit-DNA), cell-free DNA (cfDNA), and NE (neutrophil elastase) in patients with COVID-19 are increased compared with healthy individuals. B, Four months postinfection onset, plasma levels of H3Cit-DNA, cfDNA, and NE declined to those found in healthy individuals. Data are presented as median with interquartile range.

Figure 2.

Circulating markers of neutrophil extracellular trap formation are associated to disease severity and clinical outcome in patients with coronavirus disease 2019 (COVID-19). A, Plasma levels of nucleosomal citrullinated histone H3 (H3Cit-DNA), cell-free DNA (cfDNA), and NE (neutrophil elastase) in patients with COVID-19 increase with increased need for respiratory support. B, Plasma levels of H3Cit-DNA, cfDNA, and NE were all lower in survivors compared with nonsurvivors. Data are presented as median with interquartile range.