A biomarker for Long Covid may have been found!

Scientists at the University of Cambridge in the UK have found that consistently high levels of an immune molecule called interferon-gamma are associated with a subset of Long Covid patients.

According to the World Health Organization (WHO), at least 65 million people worldwide are still living with Long Covid. This represents one in every 10 people who have contracted Covid-19.

Long Covid is defined by the WHO as the continuation or development of new symptoms three months after the initial Covid infection, with these symptoms lasting for at least two months without any other explanation.

Scientists continue to research different aspects of Long Covid. However, one of the main things they are looking for is a measurable biomarker.

The discovery of a Long Covid biomarker is considered a significant step forward in diagnosing patients, monitoring their treatment, and debunking the theory that Long Covid is a psychological illness.

Dr. Nyarie Sithole, an Infectious Diseases Clinician at the University of Cambridge in the UK, established one of the first Long Covid clinics in May 2020.

The clinic at the world-renowned Addenbrooke's Hospital in Cambridge has sought to identify potential biomarkers in people suffering from Long Covid, or a subset of them. In a paper published in the journal Science Advances, the clinic reported a significant development in their work this week.

Working alongside Dr. Mark Wills and Dr. Benjamin Krishna, Dr. Sithole divided the study into subgroups, as Long Covid is believed to be a disease with various syndromes.

This means evaluating the illness under many conditions rather than as a single process. Thus, not all Long Covid patients are grouped under a single biomarker.

Scientists discovered a protein known as interferon-gamma (IFN-?), which is produced by a type of white blood cell to help your immune system fight germs and protect you from diseases, in a subset of patients.

This protein emerges as an immune response when a patient first contracts Covid. Almost all patients infected with Covid-19 produce interferon-gamma and other immune molecules or cytokines.

Researchers found that in patients who recovered from Covid within a few weeks, interferon-gamma levels returned to pre-infection levels.

However, in Long Covid patients, interferon-gamma levels remained above normal levels after 12 weeks, and in some patients, even after two years.

On average, it was found that Long Covid patients had interferon-gamma levels at least 10 times higher than the control group who had not been diagnosed with the disease.

Dr. Sithole states that there is a dysregulation in the immune system of Long Covid patients and continues:

"The immune system does not return to normal levels or a normal functional state after Covid and remains in a high state of alert as if it were still under threat."

These elevated protein levels can also cause inflammation. Because they are released into the bloodstream, this inflammation can spread to various organs.

According to Dr. Sithole, the hypothesis proposed for the elevated interferon-gamma levels suggests that there may be viral fragments or viral proteins in the bodies of Long Covid patients.

"There are research groups looking at biopsies taken from the colon and other parts of the body to see if they can detect the virus in these areas.

"These may be at a very low level, they may still be replicating, or these proteins may be in circulation and causing the immune system to constantly think there is a pathogen (germ) in the body."

Another hypothesis is that the results could be caused by autoantibodies.

Normally, people's immune systems create antibodies to fight diseases. However, sometimes the body turns on itself and creates autoantibodies that attack healthy cells.

There is existing evidence that persistent interferon-gamma release occurs following some other diseases, such as glandular fever. It is also known that in other diseases, interferon-gamma causes symptoms such as fatigue, joint pain, muscle aches, and fever.

Dr. Sithole and her colleagues analyzed various cytokines (immune molecules) in the blood of patients before the rollout of vaccines in the UK and compared this with blood samples taken after people were vaccinated.

Some, though not all, patients with elevated interferon-gamma returned to normal baseline levels after vaccination.

Furthermore, a significant portion of patients with Long Covid observed a reduction in their symptoms after vaccination.

Further research involving larger groups is needed.

However, this study shows a correlation between the reduction of interferon-gamma and the improvement of symptoms.

Therefore, this study raises hopes that interferon-gamma could be used to diagnose and monitor some Long Covid patients.