A functionally distinct neutrophil landscape in severe COVID-19 reveals opportunities for adjunctive therapies

Acute respiratory distress syndrome (ARDS) is a life-threatening syndrome of respiratory failure and diffuse alveolar damage that results from dysregulated local and systemic immune activation, causing pulmonary vascular, parenchymal and alveolar damage. SARS-CoV-2 infection has become the dominant cause of ARDS worldwide, and emerging evidence implicates neutrophils and their cytotoxic arsenal of effector functions as central drivers of immune-mediated lung injury in COVID-19 ARDS. However, a key outstanding question is whether COVID-19 drives a unique program of neutrophil activation or effector functions that contributes to the severe pathogenesis of this pandemic illness, and whether this unique neutrophil response can be targeted to attenuate disease. Using a combination of high-dimensional single cell analysis and ex vivo functional assays of neutrophils from patients with COVID-19 ARDS compared to non-COVID ARDS (caused by bacterial pneumonia), we identified a functionally distinct landscape of neutrophil activation in COVID-19 ARDS that was intrinsically programmed during SARS-CoV-2 infection. Furthermore, neutrophils in COVID-19 ARDS were functionally primed to produce high amounts of neutrophil extracellular traps (NETs). Surprisingly, this unique pathological program of neutrophil priming escaped conventional therapy with dexamethasone, thereby revealing a promising target for adjunctive immunotherapy in severe COVID-19.