The coronavirus targets the lungs foremost, but also the kidneys, liver and blood vessels. Still, about half of patients report neurological symptoms, including headaches, confusion and delirium, suggesting the virus may also attack the brain.
A new study offers the first clear evidence that in some people, the coronavirus invades brain cells, hijacking them to make copies of itself. The virus also seems to suck up all of the oxygen nearby, starving neighboring cells to death.
It’s unclear how the virus gets to the brain or how often it sets off this trail of destruction. Such infection is likely to be rare, but some people may be susceptible because of their genetic backgrounds or a high viral load. “If the brain does become infected, it could have a lethal consequence,” said Akiko Iwasaki, an immunologist at Yale University who led the work. The study has not yet been vetted for publication.
Scientists have had to rely on brain imaging and patient symptoms to infer effects on the brain, but “we hadn’t really seen much evidence that the virus can infect the brain, even though we knew it was a potential possibility,” said Dr. Michael Zandi, consultant neurologist at the National Hospital for Neurology and Neurosurgery in Britain. “This data just provides a little bit more evidence that it certainly can.”
Zandi and his colleagues published research in July showing that some patients with COVID-19 develop serious neurological complications.
In the new study, Iwasaki and her colleagues documented brain infection in three ways: in brain tissue from a person who died of COVID-19, in a mouse model, and in organoids — clusters of brain cells in a lab dish meant to mimic the brain’s structure.
Other pathogens — including the Zika virus — are known to infect brain cells. Immune cells then flood the damaged sites, trying to cleanse the brain by destroying infected cells.
The coronavirus is stealthier: It exploits the brain cells’ machinery to multiply, but doesn’t destroy them. Instead, it chokes off oxygen to adjacent cells, causing them to wither and die.
The researchers didn’t find any evidence of an immune response to remedy this problem. “This virus has a lot of evasion mechanisms,” Iwasaki said.
These findings are consistent with other observations in organoids infected with the coronavirus, said Alysson Muotri, a neuroscientist who has also studied the Zika virus.
The coronavirus seems to rapidly decrease the number of synapses, the connections between neurons. “We don’t know yet if that is reversible or not,” Muotri said.