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. 2021 May 14:ciab437. doi: 10.1093/cid/ciab437

Increased peripheral blood neutrophil activation phenotypes and NETosis in critically ill COVID-19 patients: a case series and review of the literature

Jorge A Masso-Silva 1,2,#, Alexander Moshensky 1,2,#, Michael T Y Lam 2,3, Mazen Odish 2, Arjun Patel 1,2, Le Xu 8, Emily Hansen 4, Samantha Trescott 4, Celina Nguyen 4, Roy Kim 4, Katherine Perofsky 4,10, Samantha Perera 1,2, Lauren Ma 1,2, Josephine Pham 1,2, Mark Rolfsen 2, Jarod Olay 1,2, John Shin 1,2, Jennifer M Dan 5,6, Robert Abbott 6, Sydney Ramirez 5,6, Thomas H Alexander 7, Grace Y Lin 8, Ana Lucia Fuentes 1,2, Ira Advani 1,2, Deepti Gunge 1,2, Victor Pretorius 9, Atul Malhotra 2, Xin Sun 10, Jason Duran 11, Mark Hepokoski 2, Shane Crotty 6, Nicole G Coufal 4, Angela Meier 12,#,, Laura E Crotty Alexander 1,2,#,
PMCID: PMC8241438  PMID: 33988226

Abstract

Background

Increased inflammation has been well defined in COVID-19, while definitive pathways driving severe forms of this disease remain uncertain. Neutrophils are known to 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 neutrophil function in COVID-19 may give insight into disease pathogenesis and identify therapeutic targets.

Methods

Blood was obtained serially from critically ill COVID-19 patients for eleven days. Neutrophil extracellular trap formation (NETosis), oxidative burst, phagocytosis and cytokine levels were assessed. Lung tissue was obtained immediately post-mortem for immunostaining. Pubmed searches for neutrophils, lung and COVID-19 yielded ten peer-reviewed research articles in English.

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 both at first measurement and across hospitalization (p<0.0001). COVID neutrophils had exaggerated oxidative burst (p<0.0001), NETosis (p<0.0001) and phagocytosis (p<0.0001) relative to controls. Increased NETosis correlated with leukocytosis and neutrophilia, and neutrophils and NETs were identified within airways and alveoli in lung parenchyma of 40% of SARS-CoV-2 infected lungs available for examination (2 out of 5). While elevations in IL-8 and ANC correlated with disease severity, plasma IL-8 levels alone correlated with death.

Conclusions

Literature to date demonstrates compelling evidence of increased neutrophils in the circulation and lungs of COVID-19 patients. importantly, neutrophil quantity and activation correlates with severity of disease. Similarly, our data shows that circulating neutrophils in COVID-19 exhibit an activated phenotype with enhanced NETosis and oxidative burst.

Keywords: Neutrophil, NETs, NETosis, COVID-19

Supplementary Material

ciab437_suppl_Supplementary_Materials

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ciab437_suppl_Supplementary_Materials

Articles from Clinical Infectious Diseases: An Official Publication of the Infectious Diseases Society of America are provided here courtesy of Oxford University Press

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