More than a year after its appearance and its spread around the world, COVID-19 continues to have devastating short and long term health effects on infected people; for example residual olfactory deadening in patients with 'long COVID.'The worrying damage of the disease on various organs are therefore still being studied by researchers.
Researchers from Inserm, the Pitié Salpêtrière University Hospitals, the CNRS and the Yale School of Medicine looked at the consequences of coronavirus infection on the central nervous system, AKA the brain. And they found out that the virus was capable of directly infecting nerve cells, hindering blood flow to the brain and damaging brain tissue. These results were published in the Journal of Experimental Medicine this January 12, 2021.
An infection that prevents good oxygenation
To study the extent and impact of coronavirus contamination on this area of the body, scientists used three different brain models organoids (lab-grown brain stem cells), genetically modified mice and autopsies of individuals who died from COVID-19.
First, the organoid model showed that SARS-CoV-2 can indeed infect and replicate in neurons—these are not destroyed, but undergo a change in their metabolism. Neighbouring brain cells, located near those affected, become oxygen-deprived and die. Moreover, the researchers identified that it is the famous ACE2 receiver which allowed the virus to enter the host's cells, the same as it does in the lungs.
In infected mice, experts also observed elevated levels of infected nerve cells. These levels are associated with major changes in how blood vessels work, disrupting the flow of oxygen to the brain. Finally, the brain sections of the three patients who died from serious complications of COVID-19—respiratory insufficiency—showed signs of tissue damage and death, also due to a lack of oxygenation of the neurons.
Discovering mechanisms, hoping for treatments
Taken together, these results confirm the cerebral growth of SARS-CoV-2 and its ability to infect neurons. They also suggest that the neurological symptoms observed in Covid-19—dizziness, confusion, stroke, coma - could be a consequence of this direct damage to the central nervous system
These new revelations help guide scientists towards a potential treatment : blocking the ACE2 protein, used by the coronavirus to enter the body with some antibodyor cerebrospinal fluid from an already affected patient could prevent neuronal infection... and lung infection at the same time! However, in the case of neurons, the role of the molecule as a gateway remains to be confirmed through further research.