Neutrophil virucidal activity against SARS-CoV-2 is mediated by NETs.

BACKGROUND: The inflammation in the lungs and other vital organs in COVID-19 are characterized by the presence of neutrophils and high concentration of neutrophil extracellular traps (NETs), which also seems to mediate host tissue damage. However, it is not known whether NETs could have virucidal activity against SARS-CoV-2. METHODS: We investigated whether NETs could prevent SARS-CoV-2 replication in neutrophils and epithelial cells, and what the consequence of NETs degradation in K18-humanized ACE2 transgenic mice infected with SARS-CoV-2. RESULTS: Here, by immunofluorescence microscopy we observed that viral particles co-localize with NETs in neutrophils isolated from COVID-19 patients or from healthy individuals and infected in vitro. The inhibition of NETs production increased virus replication in neutrophils. In parallel, we observed that NETs inhibited virus abilities to infect and replicate in epithelial cells after 24 h of infection. Degradation of NETs with DNase I prevented their virucidal effect in vitro. Using K18-humanized ACE2 transgenic mice we observed a higher viral load in animals treated with DNase I. On the other hand, the virucidal effect of NETs was not dependent on neutrophil elastase or myeloperoxidase activity. CONCLUSION: Our results provide evidence of the role of NETosis as a mechanism of SARS-CoV-2 viral capture and inhibition.