The Milieu Intérieur Project and COVID-19

Date: 18 July 2021

Researchers from the Milieu Intérieur consortium have contributed significantly to understand and provide solutions to the COVID-19 pandemic and continue to do so. Here is a non-exhaustive list of studies by the Milieu Intérieur consortium members during the COVID-19 pandemic. Below are highlights of three studies published in 2020 –

Early in the pandemic, techniques developed by the Milieu Interieur project was utilized in a study published in Science (Hadjadj et al., 2020) that demonstrated the precedence of low levels of type-I IFN in plasma in clinical worsening and transfer to intensive care.

Levels of circulating Type 1 IFN could even characterize each stage of disease, with the lowest levels observed in the most severe patients. These results suggest that in SARS-CoV-2 infection, the production of type-I IFN is inhibited in the infected host, which could explain the more frequent severe forms in individuals with low production of this
cytokine, such as the elderly or those with co-morbidities.

Another groundbreaking set of studies published in Science (Bastard et al., 2020; Zhang et al., 2020) lead by the Covid Human Genetic effort, has shown that more than 10% of
the 987 patients with life-threatening COVID-19 pneumonia examined, had auto-antibodies against interferons (IFNs) at the onset of their infection. This breakthrough, spearheaded by Jean-Laurent
Casanova and Helen Su through the Covid Human Genetic effort, has opened several perspectives into the treatment, control and vaccination for the
SARS-CoV-2 infection.

In this study, 10% of the population with life-threatening COVID-19, showed the existence of interferon auto-antibodies, but this is relatively rare in the healthy population cohort as demonstrated in the MI cohort where it was present in 0.3% of the donors. However, in these rare cases, the authors showed that these auto-antibodies are actually the u underlying reason some people get very sick, and not the consequence of the infection.