Abstract
Background Neutrophil NETosis and neutrophil extracellular traps (NETs) play a critical role
in pathogenesis of coronavirus disease 2019 (COVID-19)-associated thrombosis. However,
the extents and reserve of NETosis, and potential of thrombus formation under shear
in whole blood of patients with COVID-19 are not fully elucidated. Neither has the
role of recombinant ADAMTS13 or caplacizumab on the accumulation of NETs and thrombus
in COVID-19 patients' whole blood under shear been investigated.
Methods Flow cytometry and microfluidic assay, as well as immunoassays, were employed for
the study.
Results We demonstrated that the percentage of H3Cit + MPO+ neutrophils, indicative of NETosis,
was dramatically increased in patients with severe but not critical COVID-19 compared
with that in asymptomatic or mild disease controls. Upon stimulation with poly [I:C],
a double strain DNA mimicking viral infection, or bacterial shigatoxin-2, the percentage
of H3Cit + MPO+ neutrophils was not significantly increased in the whole blood of
severe and critical COVID-19 patients compared with that of asymptomatic controls,
suggesting the reduction in NETosis reserve in these patients. Microfluidic assay
demonstrated that the accumulation of NETs and thrombus was significantly enhanced
in the whole blood of severe/critical COVID-19 patients compared with that of asymptomatic
controls. Like DNase I, recombinant ADAMTS13 or caplacizumab dramatically reduced
the NETs accumulation and thrombus formation under arterial shear.
Conclusion Significantly increased neutrophil NETosis, reduced NETosis reserve, and enhanced
thrombus formation under arterial shear may play a crucial role in the pathogenesis
of COVID-19-associated coagulopathy. Recombinant ADAMTS13 or caplacizumab may be explored
for the treatment of COVID-19-associated thrombosis.
Keywords
NETosis - neutrophil extracellular traps - ADAMTS13 - von Willebrand factor - SARS-CoV-2
- COVID-19 - thrombosis
