US Pharm. 2023;48(1):4.

It is not uncommon for people to lose their sense of taste and smell due to a COVID-19 infection. In others, the disease has had an even stronger impact on the nervous system, with effects ranging from lasting concentration problems to strokes. Researchers led by Gregor Hutter from the Department of Biomedicine at the University of Basel and University Hospital of Basel in Switzerland recently reported new insights into the development of “neuro-COVID” in Nature Communications.

The team investigated how different severities of neuro-COVID can be detected and predicted by analyzing the cerebrospinal fluid and blood plasma of affected individuals. Their findings also offer some indications of how to prevent neurologic damage due to COVID-19.

The study included 40 COVID-19 patients with differing degrees of neurologic symptoms. To identify typical changes linked with neuro-COVID, researchers compared these individuals’ cerebrospinal fluid and blood plasma with samples from a control group. They also measured the brain structures of test subjects and surveyed participants for 13 months to identify lasting symptoms.

Particularly in the group with the most serious neurologic symptoms, the researchers identified a link with an excessive immune response. On the one hand, affected individuals showed indications of impairment of the blood-brain barrier, which the study’s authors speculate was probably triggered by a cytokine storm—a massive release of proinflammatory factors.

On the other hand, the researchers also found antibodies that targeted parts of the body’s own cells, revealing signs of an autoimmune reaction, as a result of the excessive immune response. “We suspect that these antibodies cross the porous blood-brain barrier into the brain, where they cause damage,” explained Dr. Hutter. They identified excessive activation of the immune cells specifically responsible for the brain—the microglia.

Dr. Hutter and his team also investigated whether the severity of neurologic symptoms is also perceptible in brain structures. They discovered that people with serious neuro-COVID-19 symptoms had a lower brain volume than healthy participants at specific locations in the brain and particularly at the olfactory cortex, the area of the brain responsible for smell.

“We were able to link the signature of certain molecules in the blood and cerebrospinal fluid to an overwhelming immune response in the brain and reduced brain volume in certain areas, as well as neurologic symptoms,” said Dr. Hutter, adding that it is now important to examine these biomarkers to develop a blood test that can predict serious cases.

These same biomarkers point to potential targets for drugs aimed at preventing consequential damage due to a COVID-19 infection. One of the biomarkers, factor MCP-3, plays a key role in the excessive immune response, and Dr. Hutter believes there is the potential to inhibit this factor medicinally at an early stage.

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