THE ESSENTIAL
- Endogenous retroviruses are sequences of the human genome having analogies with retroviruses
- These endogenous retroviruses are generally inactive and non-pathogenic, but SARS-CoV-2 might reactivate one of them
The SARS-CoV-2 responsible for the Covid-19 pandemic has not yet revealed all its mysteries. The latest discovery concerning it, made by French, Spanish and Mexican researchers, suggests that this coronavirus would awaken an endogenous retrovirus and that it is this mechanism which might be at the origin of the severe forms of Covid-19. The study – awaiting review – has been published on medRxiv.
The term retrovirus is frightening: these viruses replicate by integrating into the genome of the host cell and the best known of them is none other than HIV, responsible for AIDS. But endogenous retroviruses – sequences of the human genome having analogies with certain retroviruses – are generally inactive and without pathogenic consequences for the organism. Except that the famous S protein of SARS-CoV-2 would be able to reactivate HERVs, genes of one of these endogenous retroviruses, dormant in the human genome. And thus cause the serious forms of Covid-19.
T cells carrying traces of HERV
It was from an in-vitro experiment that scientists identified this mechanism. They analyzed and compared blood cells infected with some with SARS-CoV-2 and others with only the S protein of the coronavirus, the one that allows it to infect the cells of the body. And for all the blood cells analyzed in the experiment, the T cells produced in response to the infection carried traces of HERV.
If this phenomenon does not seem to concern all people infected with SARS-CoV-2 -HERVs were only detected in 20 to 30% of patients who tested positive-, they are found in all patients hospitalized for severe forms of Covid. And above all, by analyzing data from heart, lung and brain tissue from people who died of the disease, the researchers observed the presence of HERV.
They therefore conclude “that a percentage of people with a susceptibility to severe disease progression might be linked to the activation of HERV”. This would make these endogenous viruses thus reactivated both biological markers of severe forms of Covid but also the potential target of new treatments.
