Self-sustaining IL-8 loops drive a prothrombotic neutrophil phenotype in severe COVID-19.

Rainer Kaiser,Christian Schulz,Ralf Zimmer,Philipp Mertins,Raphael Escaig,Benjamin Schubert,Norbert Hübner,Kathrin Saar,Johannes C Hellmuth,Anouk Engel,Stefan Kääb,Maximilian Muenchhoff,Christoph Gold,Konstantin Stark,Sophia Brambs,Vivien Polewka,Viktoria Knottenberg,Clemens Scherer,Alexander Leunig,Afra Anjum,Leo Nicolai,Sven Stockhausen,Kami Pekayvaz,Mohamed Haji,Anna Titova,Anne Hilgendorff,Markus Joppich,Oliver Popp,Marie‐Louise Hoffknecht ,Steffen Maßberg

doi:10.1172/jci.insight.150862

Abstract

Neutrophils provide a critical line of defense in immune responses to various pathogens, inflicting self-damage upon transition to a hyperactivated, procoagulant state. Recent work has highlighted proinflammatory neutrophil phenotypes contributing to lung injury and acute respiratory distress syndrome (ARDS) in patients with coronavirus disease 2019 (COVID-19). Here, we use state-of-the art mass spectrometry–based proteomics and transcriptomic and correlative analyses as well as functional in vitro and in vivo studies to dissect how neutrophils contribute to the progression to severe COVID-19. We identify a reinforcing loop of both systemic and neutrophil intrinsic IL-8 (CXCL8/IL-8) dysregulation, which initiates and perpetuates neutrophil-driven immunopathology. This positive feedback loop of systemic and neutrophil autocrine IL-8 production leads to an activated, prothrombotic neutrophil phenotype characterized by degranulation and neutrophil extracellular trap (NET) formation. In severe COVID-19, neutrophils directly initiate the coagulation and complement cascade, highlighting a link to the immunothrombotic state observed in these patients. Targeting the IL-8–CXCR-1/-2 axis interferes with this vicious cycle and attenuates neutrophil activation, degranulation, NETosis, and IL-8 release. Finally, we show that blocking IL-8–like signaling reduces severe acute respiratory distress syndrome of coronavirus 2 (SARS-CoV-2) spike protein–induced, human ACE2–dependent pulmonary microthrombosis in mice. In summary, our data provide comprehensive insights into the activation mechanisms of neutrophils in COVID-19 and uncover a self-sustaining neutrophil–IL-8 axis as a promising therapeutic target in severe SARS-CoV-2 infection.

Highlights

Neutrophils are first responders to invading pathogens, with either their absence or dysfunction resulting in an immunocompromised state [1]
Because neutrophils are a main cellular factor contributing to disease progression in COVID-19, we set out to investigate their functional status at the protein level in patient samples
Patients with COVID-19 requiring normal ward inpatient hospital care were grouped into the intermediate cohort (Int), patients requiring additional invasive ventilation or intensive care treatment were included in the severe cohort (Sev)

Summary

Introduction

Neutrophils are first responders to invading pathogens, with either their absence or dysfunction resulting in an immunocompromised state [1]. Neutrophils are quickly recruited, ameliorate local tissue damage, and limit systemic viral spread by contributing to both clearance of infected tissue and production of antiviral cytokines [2, 3]. The excessive release of neutrophil extracellular traps (NETs) and cytotoxic granule contents contributes to self-inflicted damage to both local and remote organs [4,5,6]. This process of immunopathology is a hallmark of severe coronavirus disease 2019 (COVID-19) and contributes to respiratory failure, progressive immune dysregulation and — — death [7,8,9,10]. It is crucial to increase our understanding of immune dysregulation in critical cases of severe acute respiratory distress syndrome of coronavirus 2 (SARS-CoV-2) infection

Methods

Results

Conclusion