Had COVID? Part of the virus may remain in your brain
April 13, 2023 – If you or someone you know is suffering from “brain fog” after COVID-19, scientists now have a possible explanation – and it might not bring much comfort.
German researchers have found that part of the virus, the spike protein, remains in the brain long after the virus is gone.
These researchers found the virus’ spike protein in the brain tissue of animals and people after they died. The finding suggests that these virus fragments accumulate, stay, and trigger inflammation that causes long-lasting COVID symptoms.
About 15% of COVID patients continue to have long-term effects from the infection despite their recovery, said study lead author Ali Ertürk, PhD, director of the Institute of Tissue Engineering and Medicine. regenerative therapy at the Helmholtz Center in Munich, Germany.
Reported neurological problems include brain fog, loss of brain tissue, reduced thinking skills and memory problems, he said.
“These symptoms clearly suggest long-term damage and changes caused by SARS-CoV-2 in the brain, the exact molecular mechanisms of which are still poorly understood,” Ertürk said.
The researchers also propose a way for the spike protein to enter the brain in their preprint report published online ahead of peer review on April 5 at bioRxiv.
Delivered by circulating blood, the spike protein can stay inside small openings in the bone marrow of the skull called niches. It can also reside in brains, thin layers of cells that act as a buffer between the skull and the brain. From there, according to one theory, the spike protein uses channels to enter the brain itself.
The hope is that researchers can develop treatments that block one or more steps in this process and help people avoid long-lasting COVID-related brain problems.
“This is a very concerning report that literally demonstrates the SARS-CoV-2 spike protein in the skull-meninges-brain axis in postmortem individuals,” said Eric Topol, MD, director of the Scripps Research Translational Institute in La Jolla, California, and editor of Medscape, WebMD’s sister site for healthcare professionals.
That the spike protein builds up in structures just outside the brain and causes ongoing inflammation makes sense to Topol. Clustering of the spike proteins would trigger an immune response from this niche reservoir of immune cells that cause the inflammation associated with long COVID and symptoms such as brain fog, he said.
Thinking and memory problems after COVID infection are relatively common. A research team found 22% of people with long COVID specifically reported this problem, on average, in 43 published studies. Even people with mild COVID disease can develop brain fog later, Ertürk and colleagues note.
So why do researchers blame the spike protein and not the whole COVID virus? As part of the study, they found SARS-CoV-2 virus RNA in some people after death and not in others, suggesting the virus doesn’t need to be there to trigger the virus. brain fog. They also injected the spike protein directly into the brains of mice and showed that it could cause cell death.
The researchers also found no SARS-CoV-2 virus in brain parenchyma, the functional brain tissue containing nerve cells and non-nerve cells (called glial), but they did detect the spike protein there.
Investigators were surprised to find spike proteins in the cranial niches of people who survived COVID and later died of another cause. Ertürk, lead author and doctoral student Zhouyi Rong, and their colleagues found spike proteins in 10 of 34 skulls of people who died from non-COVID causes in 2021 and 2022.
They also discovered that COVID can alter the way proteins act in and around the brain. Some of these proteins are linked to Parkinson’s disease and Alzheimer’s disease, but have never been linked to the virus before.
Another unexpected finding was the closeness of the results in mice and humans. There was a “remarkable similarity in distribution of the viral spike protein and dysregulated proteins identified in mouse and human samples,” Ertürk said.
Testing for protein changes in the skull or meninges would be invasive but possible compared to sampling the parenchyma inside the brain. Even less invasive would be to test blood samples for altered proteins that could identify those most at risk of developing brain complications after COVID illness.
It will take more brain science to get there. “Designing treatment strategies for these neurological symptoms requires in-depth knowledge of molecules dysregulated by the virus in brain tissue,” Ertürk said.