Altered neutrophil phenotype and function in non-ICU hospitalised COVID-19 patients correlated with disease severity

  1. KBR Belchamber
  2. OS Thein
  3. J Hazeldine
  4. FS Grudzinska
  5. MJ Hughes
  6. AE Jasper
  7. KP Yip
  8. E Sapey
  9. D Parekh
  10. DR Thickett
  11. A Scott
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Abstract

Rational

Infection with the SARS-CoV2 virus is associated with elevated neutrophil counts. Evidence of neutrophil dysfunction in COVID-19 is based predominantly on transcriptomics or single functional assays. Cell functions are interwoven pathways, and so understanding the effect of COVID-19 across the spectrum of neutrophil function may identify tractable therapeutic targets.

Objectives

Examine neutrophil phenotype and functional capacity in COVID-19 patients versus age-matched controls (AMC)

Methods

Isolated neutrophils from 41 hospitalised, non-ICU COVID-19 patients and 23 AMC underwentex vivoanalyses for migration, bacterial phagocytosis, ROS generation, NET formation (NETosis) and cell surface receptor expression. DNAse 1 activity was measured, alongside circulating levels of cfDNA, MPO, VEGF, IL-6 and sTNFRI. All measurements were correlated to clinical outcome. Serial sampling on day 3-5 post hospitalisation were also measured.

Results

Compared to AMC, COVID-19 neutrophils demonstrated elevated transmigration (p=0.0397) and NETosis (p=0.0366), but impaired phagocytosis (p=0.0236) associated with impaired ROS generation (p<0.0001). Surface expression of CD54 (p<0.0001) and CD11c (p=0.0008) was significantly increased and CD11b significantly decreased (p=0.0229) on COVID-19 patient neutrophils. COVID-19 patients showed increased systemic markers of NETosis including increased cfDNA (p=0.0153) and impaired DNAse activity (p<0.0.001). MPO (p<0.0001), VEGF (p<0.0001), TNFRI (p<0.0001) and IL-6 (p=0.009) were elevated in COVID-19, which positively correlated with disease severity by 4C score.

Conclusion

COVID-19 is associated with neutrophil dysfunction across all main effector functions, with altered phenotype, elevated migration, impaired antimicrobial responses and elevated NETosis. These changes represent a clear mechanism for tissue damage and highlight that targeting neutrophil function may help modulate COVID-19 severity.

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