SEATTLE, Wash. — There have been many reports this year of recovering COVID-19 patients struggling with lingering, neurological issues like “brain fog” and overall mental fatigue. While it’s been discussed for some time that SARS-CoV-2 may have adverse effects on the brain, the “how” and “why” of this relationship has remained a mystery – until now. Researchers from the University of Washington say the coronavirus’ spike protein is indeed capable of bridging the blood-brain barrier in mice.
While mice obviously aren’t people, study authors say these findings all but confirm SARS-CoV-2 can do the same in humans. This spike protein, or S1 protein, is essentially what allows the coronavirus to enter and infect new human cells. Even by itself, S1 proteins can do serious damage by detaching from the the coronavirus and sparking harmful inflammation.
“The S1 protein likely causes the brain to release cytokines and inflammatory products,” says professor of medicine and lead study author William A. Banks in a university release.
This super intense immune response among COVID patients is called the “cytokine storm.” The immune system recognizes the virus as the major threat that it is, inciting an immune “overreaction” that appears to be causing brain fog, fatigue, and other cognitive problems in patients.
Coronavirus can cross brain barrier, just like HIV
This isn’t a unique phenomenon to COVID-19; many HIV patients deal with the same cognitive symptoms. These similarities led the research team to compare the S1 protein of SARS-CoV-2 to the gp120 protein present in HIV-1.
Sure enough, the two proteins are very, very similar. Both are glycoproteins, or proteins covered in sugars. Glycoproteins typically function as the “hands” and “feet” of infectious viruses. Both S1 and gp120 can also cross the blood-brain barrier and do toxic harm to brain tissues.
“It was like déjà vu,” Prof. Banks says in reference to the similarities between the two proteins. He’s studied the HIV gp120 protein extensively in the past. In summation, study authors speculate these findings may help explain a number of COVID-19’s more mysterious symptoms.
“We know that when you have the COVID infection you have trouble breathing and that’s because there’s infection in your lung, but an additional explanation is that the virus enters the respiratory centers of the brain and causes problems there as well,” Banks explains.
New clues to COVID’s effect on men
Also, researchers say the S1 proteins travel to the olfactory bulbs and kidneys of male patients faster than female patients. This may reveal the connection as to why men are at a higher risk of developing severe COVID-related symptoms.
“You do not want to mess with this virus,” Banks concludes. “Many of the effects that the COVID virus has could be accentuated or perpetuated or even caused by virus getting in the brain and those effects could last for a very long time.”
The study is published in Nature Neuroscience.