COVID-19's impact on the brain: Immune response may cause damage

Published on December 27th, 2022.

A small cadaver study found that the immune response to COVID-19 infection may lead to damage to blood vessels in the brain.

Previous research links COVID-19 infection to brain issues, such as “brain fog” and neurological issues.

In a very small cadaver study, researchers from the National Institutes of Health found that antibodies created by the body in response to COVID-19 infection can cause damage to blood vessels in the brain, causing neurological symptoms.

Scientists believe the discovery of antibody-driven immune complexes on endothelial cells in the brain suggests immune-modulating therapies may help long COVID patients.

As the COVID-19 pandemic continues, clinicians are learning more about the long-term effects of the disease on a person’s overall health. Some coronavirus patients continue to feel the effects of the condition months after initial infection, experiencing long COVID.

The National Institutes of Health (NIH)Trusted Source recently announced new findingsTrusted Source that may have relevance to our understanding of long-term COVID effects. Their new study states the body’s immune response to infection from COVID-19 damages blood vessels in the brain, causing neurological symptoms.

The study was recently published in the journal Brain.

COVID-19 and the brain: What we know

The new study is not the first time research has looked at the effects of COVID-19 on the brain. A previous studyTrusted Source found prior COVID-19 infection was associated with various brain changes, including a greater reduction in global brain volume. And other research showed having COVID-19 may decrease a person’s gray matter volume in the brain.

Researchers have also connected COVID-19 with neurological and mental health conditionsTrusted Source and brain complications like stroke and brain hemorrhage.

Past research also shows the coronavirus continues to impact the brain in patients experiencing long COVID symptoms, such as “brain fog” and other brain changesTrusted Source.

New research findings

Medical News Today spoke with Dr. Avindra NathTrusted Source, clinical director at the National Institute of Neurological Disorders and Stroke (NINDS) at the National Institutes of Health (NIH) and the present study’s senior author.

According to Dr. Nath, an earlier studyTrusted Source found evidence of blood vessel damage in the brains of COVID-19 patients who died shortly after contracting the virus, but no signs of SARS-CoV-2 infections.

“This study was undertaken to explore how COVID-19 harms the brain’s blood vessels,” Dr. Nath said.

For this study, Dr. Nath and his research team examined the brain tissue of nine COVID-19 patients who died suddenly after contracting the disease. The scientists observed evidence that antibodiesTrusted Source created by the body in response to COVID-19 infection attacked the brain’s blood vessels, causing inflammation and damage.

“Our findings suggest that the damage to the brain’s blood vessels results from the body’s natural inflammatory response to SARS-CoV-2,” Dr. Nath explained. “For the first time, we observed deposits of immune complexesTrusted Source — molecules formed when antibodies bind antigens — on the surface of cells that make up the blood-brain barrier.”

“We hypothesize that an antibody-mediated attack triggered by the virus damages the blood-brain barrier, causing blood to leak from blood vessels in the brain,” he continued. “This, in turn, triggers inflammation that damages and destroys neuronsTrusted Source.”

Why would these antibodies attack the lining of the blood vessels? Dr. Naths says they do not yet know. “One possibility might be that they are targeted against the ACE2 receptorTrusted Source of the virus, which is highly expressed in these cells,” he said.

While the study only looked at neurovascular damage in fatal cases of COVID-19, Dr. Nath said his team suspects that had these individuals lived, they would have had neurological symptoms of long COVID, including headaches, memory impairment, and brain fog.

“Those with long COVID may have a similar immune response that lingers and damages neurons,” he added. “The discovery of immune complexes on endothelial cellsTrusted Source suggests that immune-modulating therapiesTrusted Source may help.”

More long COVID research needed

As for the next steps to this research, Dr. Nath said the pathology of long COVID still needs studying.

“It’s very hard to study the brain changes driving long COVID without access to brain tissue at autopsy, but long COVID is not a fatal disease,” he explained. “Therefore, we must explore other approaches to deciphering the causes of long COVID. High-resolution MRI scans may provide insight into the neurological symptoms experienced by individuals with long COVID.”

Dr. Santosh Kesari, a neurologist at Providence Saint John’s Health Center in Santa Monica, CA, and regional medical director for the Research Clinical Institute of Providence Southern California agreed more research is required surrounding long COVID and its effects on the brain.

“We worry about the lungs and the damage that COVID causes to lungs, but COVID is actually causing inflammation and organ dysfunction elsewhere in the body that’s unappreciated,” Dr. Kesari told MNT.

“This report and others like this since the pandemic show that there also is a direct injury in the brain. That has implications for treatment approaches when we see these brain problems in our patients acutely, but also now chronically. Some long COVID patients may be having symptoms — short-term memory loss, brain fog, etc. — because of some inflammation that occurred in the brain of these patients, whether we knew it early on or not,” Dr. Kesari explained.

“And the question really is how can we understand that better?” Dr. Kesari added. “We really need to study it a lot more and understand the timing of COVID infection, the severity of the initial infection, and how that relates to brain inflammation, and the severity and duration of cognitive issues that occur in long COVID patients.”

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