Role of the balance NET/DNase in COVID-19 severity – CORONET

Infection with COVID-19 leads to variable types of symptoms, starting with asymptomatic forms to severe acute respiratory distresses (ARDS) and death. Knowing who is at high risk to aggravate, and thus requires therapeutic intervention and closer monitoring would be very useful. We recently demonstrated that early quantification of biomarkers of neutrophil extracellular traps (NETs) could predict death and vascular complications in COVID-19 hospitalized patients. NETs are the main actors of immunothrombosis, which is a physiological innate immune response that leads to formation of thrombi inside blood vessels in order to contain and destroy pathogens such as bacteria, fungi and virus. NETs are made of cell free DNA (cfDNA) fragments with histones and neutrophil proteins such as myeloperoxidase. Many evidences are in favour of an uncontrolled activation of NETosis in severe forms of COVID-19. In a physiological setting, NETs are destroyed by monocyte-produced deoxyribonucleases (DNase-1 or -1l3). Our preliminary results are in favour of an absence of upregulation of DNase activity in severe forms of COVID-19.
In the CORONET project, we aim at (1) addressing whether increased NET biomarkers predict for requirement of oxygen support in newly diagnosed COVID-19 symptomatic outpatients, (2) investigating whether decreased DNase activity correlates with increased NET biomarkers and respiratory failure, and (3) investigating the mechanisms responsible for decreased DNase activity.
In workpackage (WP)1, we will quantify NET biomarkers in 100 newly diagnosed COVID-19 symptomatic outpatients included in the “no treatment” arm of the COVERAGE study (Clinical Trial: NCT04356495). We expect to have these results within 6-7 months after the beginning of the project. In WP2, we will measure DNase activity in 64 COVID-19 hospitalized patients (32 ARDS and 32 non-ARDS) and patients from WP1 and correlate with NET markers and clinical outcome. We will use the COLCOV19 Biobank in Bordeaux (Clinical Trial: NCT04332016), which will allow us access to samples from COVID-19 patients hospitalized in the university Hospital of Bordeaux. We expect to have these results within 7-8 months after the beginning of the project. Lastly, in WP3, we will quantify DNase 1 and DNase 1like3 proteins in the patients from WP2 for whom we found an inappropriate regulation of DNase activity. This will allow us to identify patients with quantitative or qualitative defects of DNase regulation. To address the reasons for these defects, we will sequence the coding region of DNase 1 and DNase1l3 and, for the patients with quantitative defect, their regulatory regions. Another hypothesis we will consider is the presence of autoantibodies against DNase and the hypothesis of monocytes anergy. We will have the answer of WP3 at the end of the 12 months after the start of the project.
This project fulfils the axis “disease physiopathogeny” and may open the way to new therapeutic perspectives to reduce NETs, including administration of exogenous DNase (already available in the pharmaceutical industry).