Coronavirus may be capable of directly invading the brain, claims a new study published on September 9, 2020. The study noted that headaches, confusion and delirium experienced by some of the COVID-19 patients may be a result of the same.
Though the research is still in its preliminary stage, it offers several new evidence to support a largely untested theory. The research paper was led by Yale immunologist Akiko Iwasaki. The paper is still yet to undergo peer review.
As per the study, COVID-19 virus is capable of replicating inside the brain and its presence can starve nearby brain cells of oxygen, though the prevalence of this is not yet clear.
Can COVID-19 really invade brain?
According to S Andrew Josephson, Chair of Neurology Department at the University of California, it wouldn’t be completely shocking if SARS-CoV-2 virus is capable of breaching the blood-brain-barrier, a structure that surrounds the brain’s blood vessels and protects it from foreign substances.
Josephson praised the techniques used in the study and said that understanding whether or not there is direct viral involvement of the brain is extraordinarily important. He however, added that he would remain cautious until the paper underwent peer review.
Another virus, Zika virus, also has the capability of breaking the barrier and cause significant damage to the brains of fetuses.
The Study: Key Highlights
Yale immunologist Akiko Iwasaki along with his colleagues decided to approach the question of whether coronavirus invades the brain in three ways:
– By infecting lab-grown mini-brains known as brain organoids
– By infecting mice
– By examining the brain tissues of COVID-19 patients who had died
Study of Brain organoids
• In case of brain organoids, the research team found that the SARS-CoV-2 virus can infect neurons and hijack the neuron cell’s machinery to make replicate itself. The infected cells in turn caused the death of surrounding cells by choking their oxygen supply.
• One of the main arguments against the theory of coronavirus invading the brain directly had been that the brain lacks high levels of a protein called ACE2 that the coronavirus latches on to and which is found in abundance in other organs like the lungs.
• However, the research team found that the brain organoids had enough ACE2 to enable the entry of the virus and the proteins were also present in the brain tissue of deceased COVID-19 patients.
• The researchers also performed a spinal tap on hospitalized COVID-19 patients suffering from delirium. They found that the patients had neutralizing antibodies against the virus in their spinal fluid, which gave further evidence in favor of their theory.
Study of infected mice
• The research team later studied two groups of mice, one set that was genetically altered so it had ACE2 receptors in only its lungs and the other had it only its brain.
• The mice that were infected with the virus in their lungs showed some signs of lung injury, while those infected in the brain lost weight rapidly and quickly died, indicating potentially heightened lethality when the virus enters the brain.
Study of brain tissues of deceased COVID-19 patients
• The researchers later examined the brain of three patients who died from severe COVID-19 related complications, finding evidence of the virus in varying degrees.
• Their study revealed that the infected regions did not show signs of having been infiltrated by immune cells such as T-cells, which rush to kill the infected cells in case of other viruses like Zika or herpes.
• This reveals that the overloaded immune response known as cytokine storm, which is responsible for most of the damage seen in the lungs of COVID -19 patients, might not be the main cause of neurological symptoms.
• The study’s hypothesis indicates that the nose could provide the virus with a pathway to the brain. However, the study’s authors have stated that this needs to be validated through more study. They added saying that more autopsies will be required to learn about how prevalent brain infection might be.
Until now, doctors believed that the neurological impacts seen in about half of the COVID-19 patients were a result of an abnormal immune response known as a cytokine storm that causes inflammation of the brain, instead of the virus invading directly. – Jagran Josh