If, in the majority of cases, Covid-19 is a mild disease (or even asymptomatic), there are still serious forms: over the last 7 days, 1,245 patients have been admitted to critical care in France, including 935 in intensive care.
How to explain that some people develop a severe form of Covid-19 while others will have few (or no) symptoms? Researchers from Inserm, the University of Paris and the AP-HP have (perhaps) an answer to provide.
In Franco-American works published in the specialized journal Science Immunology, the researchers indeed support the hypothesis of an immunological and genetic predisposition to severe forms of Covid-19.
Genetic variation and autoantibodies that promote severe forms of Covid-19
First info: after studying medical data from 400 research centers in 38 different countries, scientists have identified variants of the TLR7 gene capable of reducing the immune response to the SARS-CoV-2 coronavirus. “This gene plays a major role in the mechanism of production of IFN 1 [interféron de type 1]. This IFN 1 deficit [empêche] cells to fight against Sars-Cov-2 infection, thus explaining the severe forms“explain the specialists.
Results : “1.3% of severe forms of Covid-19 are explained by genetic abnormalities of the TLR7 gene in men. This deficit is more frequent (1.8%) in patients under the age of 60“.
Second info: according to scientists, “15% to 20% of severe forms are caused by the presence – in the blood of patients – of autoantibodies that specifically target type 1 interferons (IFN 1)“. These autoantibodies, which”lead to severe pneumonia“, would be extremely rare before the age of 65 – which could explain why the serious forms of Covid-19 mainly concern seniors.
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