5:00 PM
Sunday 13 September 2020
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Books – Sayed Metwally
Coronavirus primarily targets the lungs, as well as the kidneys, liver, and blood vessels, however, about half of patients report neurological symptoms, including headache, confusion and delirium, indicating that the virus may also attack the brain.
A new study provides the first clear evidence that, in some people, the coronavirus invades brain cells to make copies of itself. The virus appears to absorb all the oxygen close to it, which leads to the destruction of neighboring cells to the brain until their death, according to the British newspaper, “the independent”.
It is unclear how the virus gets to the brain, it is possible that brain injury is rare, but some people may be susceptible to it due to their genetic backgrounds, high viral load, or other reasons.
“If the brain becomes infected, it could have fatal consequences,” said Akiko Iwasaki, an immunologist at Yale University who led the study.
The study was published on the Internet, and it was not examined by experts, but many researchers said that the study provides new evidence, as it shows in multiple ways that the virus can infect brain cells.
Dr Michael Zandi, a consultant neurologist at the National Hospital for Neurology and Neurosurgery in Britain, said: “Scientists have had to rely on imaging the brain and the patient’s symptoms to infer the effects, but we didn’t really see much evidence that the virus could infect the brain, even though we knew. It is possible, this data only provides more evidence that it can certainly. “
Dr Zandi and colleagues published research in July that showed that some patients with COVID-19, the disease caused by the Coronavirus, develop serious neurological complications, including nerve damage.
In the new study, Iwasaki and her colleagues documented an infection in the brain in three ways, in the brain tissue of a person who died from corona, in a mouse model, and in organoids – clusters of brain cells in a lab dish that aims to simulate the three-dimensional structure of the brain.
Other pathogens – including the Zika virus – are known to infect brain cells, and then immune cells overwhelm the damaged sites, in an attempt to cleanse the brain by destroying the infected cells.
Corona virus is more secretive, it exploits the mechanism of brain cells to reproduce, but it does not destroy them, instead, it prevents oxygen from reaching neighboring cells, which leads to their wilting and death.
The researchers found no evidence of an immune response to treat this problem, Iwasaki said. “It’s a kind of silent infection. This virus has a lot of evasion mechanisms.”
These results are consistent with other observations in organs infected with the Coronavirus, said Alison Motory, a neuroscientist at the University of California, San Diego, who has also studied the Zika virus. The coronavirus appears to rapidly reduce connections between nerve cells.
He adds: “Days after infection, we are already witnessing a significant decrease in the amount of synapses. We do not yet know whether this is subject to change or not. The virus infects a cell through a protein on its surface called ACE2, this protein appears throughout the body.” Especially in the lungs, “explaining why they are preferred targets for the virus.
Previous studies have suggested that the brain has very little ACE2 and it is likely to survive, but Iwasaki and her colleagues looked closely and found that the virus could actually enter brain cells using this input, and Iwasaki said: “It is clearly expressed in neurons and is essential. To enter. “
Then her team looked at two groups of mice – one containing ACE2 receptors expressed only in the brain, and the other with the receptor in the lungs only. When they introduced the virus into these mice, the brain-infected mice lost weight quickly and died within six days. The mice with lung disease did not. that.
Despite the warnings associated with the mouse studies, the results still indicate that a viral infection in the brain may be more deadly than a respiratory infection, Iwasaki said.
The virus may reach the brain via the olfactory bulb – which regulates smell – through the eyes or even from the bloodstream. It is not clear what path the cause of the disease takes, and whether it does so often enough to explain the symptoms that appear in people.
Researchers will need to analyze several autopsy samples to estimate the extent of the brain infection, and whether it is present in people with mild symptoms of corona.
Dr. Robert Stevens, a neurologist at Johns Hopkins University, said that between 40 to 60 percent of Corona patients suffer from neurological and psychological symptoms, but the symptoms may not all stem from the virus that invades brain cells, and it may be the result of inflammation spread throughout the body .
For example, inflammation in the lungs can lead to the release of particles that make the blood sticky and lead to clogging of blood vessels, leading to strokes, said Dr. Zandi: “There is no need for the brain cells themselves to become infected for this to happen.”
But he added that in some people, it may be the lack of oxygen in the blood from affected brain cells that causes the strokes: “Different groups of patients may be affected in different ways.”
Some symptoms, such as brain fog and delirium, can be difficult to recognize in patients who are sedated and on ventilators.
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