Paris (AFP)
Nearly 15% of severe forms of Covid-19 are explained by genetic and immune abnormalities leading to the failure of a powerful antiviral molecule, naturally produced by the body in the event of infection, according to the work of a French team -american.
This discovery could make it possible to screen people at risk of developing a serious form and to better treat them, according to the researchers.
This research, which specifically points to a defect affecting proteins of the immune system, type 1 interferons (IFNs), are detailed in two articles published by the American journal Science.
"This is a defect in the production or action of type 1 interferons", underlines Professor Jean-Laurent Casanova (Imagine Institute, Paris and Rockefeller University in New York).
Researchers have demonstrated in some patients genetic abnormalities (mutations of 13 genes) which decrease the production of type I IFNs (3-4% of severe forms).
They also identified in other patients aged 25 to 87 a form of autoimmune disease, in this case the presence at very high levels in the blood of misdirected antibodies, called autoantibodies. .
These neutralize the anti-viral action of type 1 IFNs (in at least 10% of severe forms of Covid) instead of attacking the virus.
This anomaly affects more men than women, according to the study, while autoimmune diseases (dysfunction of the immune system that causes it to attack some of its normal constituents) generally affect women much more. .
The study also suggests that the frequency of these antibodies increases with age.
Prof. Casanova led this research with Prof. Laurent Abel (Imagine Institute / Inserm), in collaboration with Helen Su from the American National Institute of Allergies and Infectious Diseases (NIAID / NIH).
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