COVID-19: the brain may be affected, researchers confirm

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An international study involving several teams of researchers confirms the ability of SARS-CoV-2 to infect neurons and identifies several consequences.

A growing body of scientific data suggests that the SARS-CoV-2 virus is not without consequences for our brains. Thus, beyond the significant respiratory damage that SARS-CoV-2 infection can cause, neurological symptoms were also reported very rapidly in patients, from headaches to loss of smell or more serious loss of consciousness and stroke.

A recent study by researchers at the National Institutes of Health (United States) suggests the possibility of blood vessel damage and inflammation after examining brain tissue samples from patients who died shortly after contracting the disease.

But if traces of RNA from the virus have been found in the brains of patients who died from Covid-19 and viral proteins in certain cells of their olfactory bulb, the ability of the virus to infect brain cells and the possible consequences had not been demonstrated until then.

To meet this challenge, a team of researchers from Yale University (USA) and several French organizations used three different approaches to study the infection in the brain: 3D brain cell cultures, a mouse model of SARS-CoV-2 infection and brain tissue from deceased patients with Covid-19.

The results in 3D brain cell cultures demonstrated SARS-CoV-2s ability to enter neurons and use its components to multiply. This then causes metabolic changes in the infected cells, without destroying them. Furthermore, cells neighboring the infected neurons are deprived of oxygen and eventually die. Regarding the brains of patients who died from Covid-19, the virus was found in cortical neurons, as well as pathological damage associated with the infection such as ischemic strokes, death of brain tissue due to insufficient supply of blood and oxygen to the brain.

But how the virus enters neurons is another question. According to the researchers, previous data has shown that in the rest of the body, the virus uses the protein ACE2, which is found on the surface of cells. This is particularly expressed in the lungs, which explains why the coronavirus attacks this organ more specifically. However, this pathway has not yet been demonstrated in neurons. Thanks to a mouse model of SARS-CoV-2 infection, which also has a receptor for the ACE2 protein, which is the focus of attention, the researchers were able to confirm the importance of this route of entry for the infection of brain cells. .

When neurological symptoms persist

Finally, the analysis also revealed that the infected brain regions in the mice studied exhibited significant remodeling of the cerebral vascular network. Therefore, the researchers believe that there could be a link between the penetration of the virus into neurons seen in brain cell cultures and in post-mortem brain tissue, and the hypoxia and ischemic attacks seen in the brains of patients. "These results confirm the brain tropism of SARS-CoV-2 and its ability to infect neurons. The neurological symptoms observed in Covid-19 could be a consequence of this direct attack on the central nervous system," they conclude.

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