by Scientists have identified a persistent change in a handful of blood proteins in people with prolonged Covid, indicating that an important part of their immune system remains on alert for months after an acute infection.
The findings, published Thursday in the journal Science, could help explain what causes the persistent fatigue, brain fog and other debilitating symptoms of prolonged Covid, as well as pave the way for diagnostic tests and b ‘maybe, a long-awaited treatment, experts say.
The study followed 113 Covid patients for up to a year after they were first infected, along with 39 healthy controls. At the six month mark, 40 patients had developed prolonged Covid symptoms.
Blood samples repeatedly revealed important differences in their blood: A group of proteins indicated that a part of the body’s immune system known as the complement system remained activated long after it had returned to normal.
“When you have a viral or bacterial infection, the complement system is activated and binds to these viruses and bacteria and then kills them,” said Dr. Onur Boyman, professor of immunology at the University of Zurich in Switzerland and one of the researchers who conducted the study. investigators. The system then returns to its resting state, where its normal job is to clear the body of dead cells, he said.
But if the complement system remains in its microbe-fighting state after eliminating the viruses and bacteria, “it starts to damage healthy cells,” he said.
“These can be endothelial cells that line the inner layers of blood vessels, blood cells themselves, and cells in various organs, such as the brain or lungs,” he continued. The result is tissue damage and microclots in the blood.
Previous studies have documented blood clotting and tissue damage in people with prolonged Covid. “But this research gets to the molecular mechanism of how that might be initiated,” said Akiko Iwasaki, a professor of immunobiology and molecular, cellular and developmental biology at the Yale School of Medicine, who was not involved in the a new study.
Tissue damage as well as blood clots can lead to disabling symptoms of prolonged covid, including exercise intolerance.
During exercise, the heart pumps more blood and stimulates the endothelial cells inside the blood vessels, which are everywhere in the body, Boyman said.
“In healthy people, the normal endothelial cells can take these changes, but the inflamed endothelial cells in long-term Covid patients cannot,” he said.
Iwasaki noted that microclots can reduce the level of oxygen and nutrients delivered to various organs.
“If your brain, for example, isn’t getting enough oxygen, obviously there’s going to be a lot of problems with memory, brain fog and fatigue,” she said.
Possible route to tests and treatments
Just over 14% of adults in the United States report having ever experienced Covid, according to the latest data from the US Census Bureau’s Household Pulse Survey.
Dr. Monica Verduzco-Gutierrez, chair of rehabilitation medicine at the University of Texas Health Science Center at San Antonio and head of its longstanding Covid clinic, praised the new study.
“Understanding the long-term mechanisms of Covid is about discovering treatments,” she said.
Other studies have also identified potential mechanisms. In one study, published in the October issue of the journal Cell, researchers suggested that remnants of the virus stuck in long-term Covid patients triggered reductions in the neurotransmitter serotonin. Lower serotonin levels, they said, may explain some neurological and cognitive symptoms. Another study, published in the journal Nature in September by Iwasaki and her colleagues found that long-term Covid patients had significantly lower levels of the hormone cortisol than other Covid patients and healthy controls. Cortisol helps people stay alert and awake.
Verduzco-Gutierrez, Iwasaki and Boyman agree that the new research points the way toward developing diagnostic tests and treatment by targeting proteins of the complement system.
However, Boyman and his colleagues used sophisticated, cutting-edge methods to detect the differences between these proteins that could not be used in a standard diagnostic laboratory.
“We need companies that are already active in diagnostics that have enough manpower and financial power” to develop a simplified test, he said.
Once a test is developed, or with intensive screening for long-term Covid patients, pharmaceutical companies could begin clinical trials of potential treatments, Boyman said. There are already drugs to modulate and suppress the complement system for very rare immune diseases that affect the kidneys, muscles or nervous system, and they could be tested in long-term Covid patients, he said .
New drugs could also be developed, Iwasaki said.
“I think there are a lot of things we can try in the future,” she said. But first, the results of this study need to be replicated, as with any research, she said.
Verduzco-Gutierrez said she would like any future studies to follow patients for a longer period of time. “What about people who have had Covid for three years? We don’t know what their blood looks like,” she said.
This article was originally published on NBCNews.com
