According to a study still in pre-publication, a protein encoded by an endogenous human retrovirus is reactivated by SARS-CoV-2. The latter would be involved in the appearance of severe forms of Covid-19.
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[EN VIDÉO] 22% of the population would be more vulnerable to complications from Covid-19 About 1.7 billion people, or 22% of the world’s population, are thought to be suffering from health conditions that can cause complications in the event of infection with the Covid-19 virus. This is the result of a study posted online by the CDC based on readings collected throughout April 2020 in the United States.
SARS-CoV-2 is capable of reactivating Genoa of retroviral origin, HERVs, dormant in the human genome. If the HERVs no longer produce virions infectious, they are not inactive. In April 2021, italian scientists had made the link between the serious cases of Covid-19 and the presence of HERV-W ENV, the protein of envelope encoded by a type W HERV, in the lymphocytes T. The presence of these cells is correlated with theinflammation and the gravity from symptoms patients’ respiratory tract. But this study did not light the mechanism behind this observation. Who is responsible for enabling HERV-W?
A response was proposed on January 21, 2022 in a prepublication, still awaiting peer review, available on medRxiv. According to experiments carried out by French, Spanish and Mexican researchers, the S protein of SARS-CoV-2 can trigger the transcription of several HERVs, but only the envelope protein encoded by HERV-W is present in the cells.
An endogenous human retrovirus reactivated by SARS-CoV-2
This was demonstrated in an experiment in vitro where the blood mononuclear cells have been infected with SARS-CoV-2 or only the S protein. A few hours later, the T lymphocytes express the HERV-W ENV protein on their surface. But the phenomenon does not concern all people with Covid-19. HERV-W ENV was only detected in 20-30% of affected patients who tested positive for SARS-CoV-2. In contrast, HERV-W ENV in the soluble form in plasma was observed in all patients hospitalized for a severe form of Covid-19 included in the study. The researchers write that “ these data suggest that a percentage of people with underlying susceptibility to symptomatic and/or severe disease course may be related to HERV-W ENV activation”.
Another observation that corroborates the previous ones, the researchers had access to samples of heart, brain and lung tissue from deceased people. of Covid-19. HERV-W ENV is present in many different cells: macrophageslymphocytes, endothelial cells that form blood vessels and surround the heart, microglia in the brain, or the nasal mucosa.
HERV-W ENV could serve as both a biomarker severe forms of Covid-19 and target for future treatments. Those currently being tested for multiple sclerosis may be of interest, as a hexameric form of HERV-W ENV also appears to be implicated in this condition. There remains, however, a question that has not yet been answered. HERV-W ENV was observed in lymphocytes, a cell type that expresses neither ACE2 nor TMPRSS2, two elements essential for the entry of SARS-CoV-2 into the cell. In this specific case, it seems to be using another gate entrance, which remains to be discovered.
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