Researchers believe they have found a biomarker in the blood for acute COVID-19, which could allow for a diagnostic test to indicate severe disease.  

The study focused on patients with acute COVID-19 and identified high levels of interleukin-26 (IL-26). This is a signaling molecule in the blood that typically promotes bacterial and host cell death, but it appears to also have a role in fighting the viral infection too. 

While vaccines are doing well at fighting off COVID-19 infection, the researchers argue that a better diagnostic test and better treatment for severely ill patients are desperately needed. 

“We need to understand more about underlying immunological mechanisms in order to find better treatments. There is also a need for improved diagnostics in COVID-19 patients,” says Eduardo Cardenas, principal author of the study, in a statement. 

The study focused on elevated signaling molecules that could indicate COVID-19 infection – in particular, cytokines involved in calling an immune response to an area. They first investigated whether (IL-26) plays any role in COVID-19 infection, as it has been implicated in virus infections before. 

Taking 49 patients that had been hospitalized with the virus (44 of which needed oxygen therapy) and 27 healthy controls, the researchers measured the number of inflammatory markers and IL-26 in their blood. 

In patients with acute COVID-19, IL-26 and other markers of inflammation were markedly raised, which correlated with “don’t eat me” signals present on immune cells. In those with high levels of IL-26, there were increased markers of tissue damage (lactate dehydrogenase). 

When these markers were higher, it strongly correlated with cytokine storms in the patients, which is a devastating and life-threatening complication involving an overactive immune system. 

The researchers believe that not only could IL-26 be a likely biomarker for acute COVID-19, but it could also be a target for new therapies.  

“We can show for the first time that blood levels of the cytokine IL-26 are much higher in patients with COVID-19 than in healthy controls,” says Dr Cardenas.    

“Our discovery gives us a potential biomarker for severe COVID-19, but given the antiviral effects of IL-26, we may also have identified a new therapeutic target,” continued co-author Professor Anders Lindén.

The study was published in Frontiers in Immunology.