Detecting Severe COVID-19 Disease Early On: Unique Immune Response Holds The Key

Can severe COVID-19 disease be predicted early on? Researchers unveil the secret to doing this bringing hope for better prognosis.

COVID-19 is an unpredictable virus, and this unpredictability is more pronounced now than ever before. During the current wave of this pandemic, many healthy, young patients are succumbing to the disease. At the same time, we are seeing many patients with comorbidities making a full recovery. So, what is it that leads to severe illness in some patients while others get off easy with a mild infection? Experts have been trying to answer this question since the beginning of the pandemic. Now researchers from the University of Zurich may have found the answer to this. They have identified the first biomarker that can reliably predict which patients will develop severe symptoms. This is positive news indeed as it can greatly improve the treatment of severe cases of COVID-19.

Measuring stick to predict severe disease

Most people who are infected with SARS-CoV-2 develop no or only mild symptoms. However, some patients suffer severe life-threatening cases of COVID-19 and require intensive medical care and a ventilator to help them breathe. Many of these patients eventually succumb to the disease or suffer significant long-term health consequences. To identify and treat patients at risk of severe disease at an early stage, a kind of "measuring stick" is needed -- predictive biomarkers that can recognize those who are at risk of developing severe COVID-19.

First biomarker to predict severity of disease identified

Researchers discovered such a biomarker -- the number of natural killer T cells in the blood. These cells are a type of white blood cell and part of the early immune response. According to them, the number of natural killer T cells in the blood can be used to predict severe cases of COVID-19 with a high degree of certainty -- even on a patient's first day in hospital.

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Better scope for targeted therapy

The new biomarker test helps clinicians decide which organizational and treatment measures need to be taken for patients with COVID-19, such as transfer to the ICU, frequency of oxygen measurements, type of therapy and treatment start. Predictive biomarkers are very useful for making these decisions. They help clinicians provide patients suffering severe symptoms with the best care possible. The findings of this study also make it possible to investigate new therapies against COVID-19, say researchers.

What causes severe disease?

According to the researchers, the rapid deterioration in the health of COVID-19 patients is caused by an overreaction of the body's immune system. The human body produces small proteins called cytokines at a much higher rate, which leads to a 'cytokine storm' and triggers massive inflammation. Immune cells invade the lungs, where they disrupt gas exchange. To detect the immune cells and cytokines in patient samples, researchers used high-dimensional cytometry. This technology enables researchers to characterize many surface and intracellular proteins in millions of individual cells and process them using computer algorithms.

Unique immune signature of COVID-19

Many pathogens can cause pneumonia and spark an immune response. But the exact nature of the immune response triggered by COVID-19 has been unclear. To characterize this response, the researchers analyzed blood samples of patients with severe pneumonia driven by a pathogen other than the novel coronavirus. By comparing the immune responses in COVID-19 patients with those of the control group, the researchers were able to determine the unique characteristics of the COVID-19 immune response. According to them, the immune responses to the various pneumonias are very similar and part of the body's general inflammatory response, as often observed in patients in intensive care. When it comes to COVID-19, however, T cells and natural killer cells display a unique behavior and describe a kind of pattern in the immune system -- the immune signature specific to COVID-19.