In a groundbreaking study published in the journal Science, scientists have uncovered a significant change in blood proteins that indicates a prolonged activation of the immune system in individuals with long Covid. The findings have the potential to explain the persistent symptoms experienced by long Covid patients, such as fatigue and brain fog, and could pave the way for diagnostic tests and even treatments.

Conducted over the course of one year, the study followed 113 Covid patients who had been infected, alongside 39 healthy controls. After six months, 40 of the patients developed symptoms of long Covid.

Upon analyzing repeated blood samples, researchers discovered important differences in the blood of long Covid patients. Specifically, a set of proteins revealed that a part of the immune system known as the complement system remained activated long after it should have returned to its normal state.

Dr. Onur Boyman, one of the investigators and a professor of immunology at the University of Zurich, explained that the complement system is typically activated during a viral or bacterial infection to eliminate the invaders from the body. However, in long Covid patients, the system remains in its microbe-fighting state, ultimately causing damage to healthy cells including those lining blood vessels, cells in the blood, and cells in organs like the brain or lungs. This can lead to tissue damage and the formation of blood clots.

While previous studies have highlighted blood clotting and tissue damage as complications of long Covid, this research sheds light on the molecular mechanism behind these issues. Dr. Akiko Iwasaki, a professor at the Yale School of Medicine, praised the study for providing insights into how these complications are initiated.

The tissue damage and blood clots resulting from the persistently activated complement system can lead to the debilitating symptoms experienced by long Covid patients, making them intolerant to exercise. During physical activity, the endothelial cells inside blood vessels are agitated, which can normally be handled by healthy endothelial cells. However, in long Covid patients with inflamed endothelial cells, these changes become problematic.

Dr. Monica Verduzco-Gutierrez, chair of rehabilitation medicine at the University of Texas Health Science Center at San Antonio, commended the study for advancing our understanding of long Covid. She emphasized the need to unravel the mechanisms behind long Covid in order to develop effective treatments.

The researchers believe that these findings hold the potential for developing diagnostic tests and treatments by focusing on the proteins of the complement system. However, the complex methods used in the study would need to be simplified before they can be implemented in routine diagnostic labs.

Once a simplified test is available or with rigorous screening of long Covid patients, clinical trials of potential treatments could be conducted. Dr. Boyman suggested exploring drugs already used to modulate and inhibit the complement system for rare immune diseases affecting the kidneys, muscles, or nervous system.

While there is promise for the future, it is important to replicate the results of this study and conduct further research. Dr. Verduzco-Gutierrez emphasized the importance of longer-term studies, especially to understand the blood profiles of individuals with long Covid over extended periods.

In conclusion, the identification of persistent changes in blood proteins provides valuable insights into the immune responses of long Covid patients. This breakthrough study may hold the key to unlocking diagnostic tests and potential treatments for the lingering effects of the virus.