The largest UK study of its kind identifies unique blood signatures in long-term COVID patients, offering new avenues for drug development

In a landmark study from the UK, researchers have uncovered blood biomarkers that correlate with the persistent and diverse symptoms of long-term COVID-19, potentially leading to more precise treatments. This research, the most extensive of its kind conducted in the UK involving hospitalized COVID-19 patients, offers hope for the development of targeted therapies.

The study, led by Imperial College London, examined individuals who had been hospitalized with severe COVID-19 and were still experiencing symptoms at least six months later. Of these, 426 patients were identified as suffering from long COVID-19, while 233 had recovered fully. The researchers analyzed blood plasma samples, focusing on 368 proteins involved in immunity and inflammation.

The findings revealed distinct patterns of blood markers consistent with ongoing immune activation in those with long COVID-19 compared to those who had recovered. These markers included elevated inflammation in the myeloid cells of the bone marrow and activity in the complement system, which typically responds to infection or tissue damage.

Dr Felicity Liew, the first author of the study, stated, “It is unusual to find evidence of ongoing complement activation several months after the acute infection has resolved, suggesting that long COVID symptoms may be a result of active inflammation.”

Moreover, the study identified five distinct symptoms “signatures” in the blood of long COVID patients: fatigue, cognitive impairment, anxiety and depression, cardiorespiratory issues, and gastrointestinal symptoms. This categorization could greatly aid in tailoring treatments more effectively, as it allows for targeted therapeutic approaches depending on the symptom cluster.

A promising area of treatment highlighted by the researchers involves the use of IL-1 antagonists, a class of drugs currently used for rheumatoid arthritis. These drugs target parts of the immune system that the study found to be activated in certain subtypes of long-term COVID-19.

While the study opens new pathways for managing long COVID, its authors acknowledge some limitations. Dr. Liew mentioned, “We can’t be sure that this is applicable to all types of long COVID, especially if symptoms occur after non-hospitalized infection.” Nevertheless, the insights gained are a significant step forward in understanding and potentially treating long COVID.

Professor Peter Openshaw, one of the lead investigators, emphasized the implications of the findings. “This work provides strong evidence that long COVID is caused by post-viral inflammation but shows layers of complexity,” he said. “We hope that our work opens the way to the development of specific tests and treatments for the various types of long COVID and believe that a ‘one size fits all’ approach to treatment may not work.”

The findings have been published in the prestigious journal Nature Immunology, marking a critical milestone in the ongoing battle against the long-term impacts of COVID-19.