Washington (AFP)

The headaches, confusion and delusions experienced by some Covid-19 patients could be the result of a direct invasion of the brain by the coronavirus, according to a study published Wednesday.

Research is still preliminary but provides clues to support what was only a largely unproven theory.

According to the study, led by Akiko Iwasaki, immunologist at Yale University, the virus is able to duplicate itself inside the brain, and its presence deprives neighboring brain cells of oxygen.

The frequency of this situation is not yet clear.

S. Andrew Josephson, head of the department of neurology at the University of California at San Francisco, praised the techniques used in the study, saying that "understanding whether or not there is direct viral involvement in the brain is extremely important. important".

He added, however, that he would remain cautious until the research was peer reviewed.

It wouldn't be entirely shocking if Sars-CoV-2 was able to penetrate the blood-brain barrier, a structure that surrounds blood vessels in the brain and tries to block foreign substances.

But doctors until now believed that the neurological consequences seen in about half of hospitalized Covid patients could be the result of an abnormal immune response - "the cytokine storm" - causing inflammation of the brain, rather than a invasion of the brain by the virus.

Professor Iwasaki and her colleagues decided to approach the issue in three ways: by infecting lab-created mini-brains (brain organoids), by infecting mice and by examining the brains of patients who have died from Covid-19.

In brain organoids, the team found that the virus was able to infect neurons and then "hack" into the neuron cell's machinery to duplicate itself.

Infected cells caused surrounding cells to die by depriving them of oxygen.

One of the main arguments against the theory of direct brain invasion was that the brain does not have high levels of a protein called ACE2, to which the coronavirus clings, and which is found in abundance in d other organs such as the lungs.

But the team found that the organoids had enough ACE2 to facilitate entry of the virus, and the proteins were also present in the brains of patients who died.

The team also looked at two groups of mice: one was genetically engineered to have ACE2 receptors only in the lungs, the other only in the brain.

Mice infected with the lungs had lesions in this organ;

the infected animals in the brain quickly lost weight and died quickly, a potential sign of increased lethality when the virus enters the brain.

The brains of three patients who died of severe complications from Covid-19 also showed traces of the virus, to varying degrees.

© 2020 AFP