Korean researchers have discovered an important biomarker to determine the severity of COVID-19, raising hope for a treatment to improve symptoms by using a glucocorticoid inhibitor like dexamethasone.

A KAIST research team led by Prof. Lee Heung-hyu at Graduate School of Medical Science and Engineering said on Monday it found the severity of COVID-19 is determined by overactivation of innate immune cell neutrophils in white blood cells, citing neutrophils and glucocorticoid hormones that regulate body functions are linked to each other.

The team analyzed single-cell genetic information in bronchial alveolar lavage fluid in patients with mild and severe COVID-19 infection. This information is shared through the Gene Expression Omnibus (GEO). The researchers found that severe COVID-19 was caused by overactivation of neutrophils, whose importance in viral infections was less known compared to the case of fungal and bacterial infections. In particular, the research team found that the influx of neutrophils increases due to chemokines expressed in bone marrow-derived immune cells such as macrophages. Chemokines are a group of secreted proteins within the cytokine family involved in leukocyte chemoattraction and trafficking of immune cells. The research team said that the expression of glucocorticoid receptors in immune cells derived from bone marrow leads to the influx of neutrophils and their activation.

COVID-19 symptoms vary from patient to patient, and it is important to predict the severity of each patient for treatment. To determine the seriousness, a reliable biomarker is required. Patients with severe COVID-19 show symptoms of acute respiratory distress syndrome, with severe damage to the lung tissue. In response, various immune cells such as neutrophils exhibit an immune response to protect the host from viral infection. However, an excessive immune response like a cytokine storm or an excessive inflammatory reaction can damage organs.

The study results were published in the online edition of Frontiers in Immunology on Aug. 28.

By Lee Jong-hwa and Minu Kim

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