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A new study provides the first clear evidence that the virus in some people invades brain cells and hijacks them to make copies of itself, and also absorbs nearby oxygen, leading to neighboring cells starving, according to the New York Times.
It is not clear how the virus reaches the brain or how often it triggers this path of destruction, and brain injury is likely rare, but some people may be susceptible to it due to their genetic backgrounds, high viral load, or other reasons.
“If the brain is infected, it can have fatal consequences,” said Akiko Iwasaki, an immunologist at Yale University in the United States, who led the work. Several researchers emphasized that the study demonstrated in multiple ways that the virus can infect brain cells.
In the new study, Dr. Iwasaki and her colleagues documented brain infection in three ways: in the brain tissue of a person who died, in a mouse model, and in the organelles of clusters of brain cells.
Other pathogens, including the Zika virus, have been known to infect brain cells and then immune cells overwhelm damaged sites in an attempt to cleanse the brain by destroying infected cells, but the more secretive Corona virus exploits the mechanism of the brain cells to reproduce, but does not destroy them. Instead, it suffocates oxygen from neighboring cells, causing them to wither and die.
The researchers found no evidence of an immune response to treat this problem, Dr. Iwasaki said, “It’s kind of a silent infection. This virus has many avoidance mechanisms.”
For her part, Alison Motory, a neuroscientist at the University of California, San Diego, who has also studied the Zika virus, added that these results are consistent with other observations in organelles infected with the Coronavirus.
And the coronavirus appears to be rapidly reducing the number of synapses and connections between neurons. “Days after infection, we are already seeing a significant reduction in the number of synapses. We don’t yet know if this is reversible or not,” Dr. Motory said.
The virus infects the cell through a protein on its surface called “ACE2”. This protein appears throughout the body, especially in the lungs. Previous studies suggested that the brain has too little ACE2, so the rate of brain injury is weak.
But Dr. Iwasaki and her colleagues looked closely and found that the virus can enter brain cells using this input. “It is clear that it is expressed in neurons and it is necessary to enter,” she said.
His team investigated two groups of mice, one containing ACE2 receptors expressed only in the brain and the other with the receptor only in the lungs.When the researchers inserted the virus into these mice, the brain-infected mice lost weight rapidly. and they died within six days, while the mice with lungs did not. Do that.
Iwasaki said that despite the caveats associated with the rat studies, the results still indicate that a viral infection in the brain may be more deadly than a respiratory infection.
And the virus can reach the brain through the olfactory bulb, which regulates smell, through the eyes or even from the bloodstream, and it is unclear which path the pathogen takes and if it does so frequently enough to explain the symptoms of people.
“I think this is a case where the scientific data is ahead of the clinical evidence,” Dr. Motory said.
Researchers will need to analyze various autopsy samples to estimate the extent of the brain infection and whether it is present in people with milder illnesses or in so-called long-distance drivers, many of whom have a variety of neurological symptoms.
In turn, Dr. Robert Stevens, a neurologist at Johns Hopkins University, indicated that between 40 and 60 percent of patients with Covid-19 in the hospital suffer from neurological and psychological symptoms, but it is possible that not all of them Symptoms stem from virus invasion into brain cells, may be the result. Inflammation spreads throughout the body.
For example, inflammation of the lungs can cause the release of particles that make the blood sticky and clog the blood vessels, leading to strokes. “Brain cells don’t have to be infected for this to happen,” said Dr. Zandi. In some people, it may be the lack of oxygen in the blood of the affected brain cells that causes strokes.
