COVID-19 neutrophils show elevated migration and NETosis, which is reduced by PI3K inhibition

Rational: Evidence of neutrophil dysfunction in COVID-19 is based on transcriptomics. Cell functions are interwoven pathways, so understanding the effect of COVID-19 across neutrophil function may identify therapeutic targets. We examined neutrophil phenotype and function in 41 hospitalised, non-ICU COVID-19 patients versus 23 age-matched controls (AMC) and 26 community acquired pneumonia (CAP) patients. Methods: Isolated neutrophils underwent ex vivo analyses for migration, phagocytosis and NETosis, and the effect of PI3K inhibition. Circulating DNAse 1 activity and levels of cfDNA were measured. Results: Compared to AMC and CAP, COVID-19 neutrophils demonstrated elevated transmigration (p=0.0397, A) and NETosis (p=0.0366, B), but impaired phagocytosis (p=0.0236, C) associated with impaired ROS generation (p<0.0001). COVID-19 and CAP patients showed increased systemic markers of NETosis including increased cfDNA (p=0.0153) and impaired DNAse activity (p<0.0.001, D). Ex vivo inhibition of PI3K γ and δ reduced NET release by COVID-19 neutrophils (p=0.0156). Conclusion: COVID-19 is associated with neutrophil dysfunction across all main effector functions, with elevated migration, impaired antimicrobial responses and elevated NETosis. These changes represent a clear mechanism for tissue damage and highlight that targeting neutrophil function via PI3k may help modulate COVID-19 severity.