Altered characteristics of granulocytes in COVID-19 patients can be linked to disease severity

COVID-19 disease severity seems to be affected by the characteristics of white blood cells called granulocytes, which are part of the innate immune system. Combined measurements of granulocytes and well-known biomarkers in the blood can predict the severity of the disease, according to a new study from Karolinska Institutet in Sweden. The results are published in the journal PNAS and may eventually contribute to more tailored treatments for COVID-19 patients.

Granulocytes are a family of white blood cells that include neutrophils, eosinophils and basophils. They are part of the so-called innate immune system, which is the body's first line of defence against pathogens. There are many studies on how SARS-CoV-2 affects various components of the immune system, but there is still a lack of knowledge about the role of granulocytes in COVID-19.

Researchers at Karolinska Institutet have now investigated the characteristics of granulocytes in the blood during the early phase of SARS-CoV-2 infection in a total of 26 hospitalised patients with COVID-19 at the Karolinska University Hospital. They also performed follow-up analyses four months after hospital discharge and compared these with analyses of healthy uninfected individuals.

Our study shows significantly altered characteristics of all granulocyte subsets in COVID-19 patients and this can be linked to the severity of the disease."

Magda Lourda, lead author, researcher, Department of Medicine, Huddinge, Karolinska Institutet

Combined measurements of granulocyte characteristics and widely used biomarkers in the blood called C-reactive protein (CRP) and creatinine, could predict key clinical features such as respiratory function and multiorgan failure.

"The finding needs to be taken with caution considering the limited size of our study cohort, but our hope is that these combined measurements can be used to predict the severity of the disease, resulting in more tailored treatments for COVID-19 patients," says Magda Lourda.

The study is part of the Karolinska KI/K COVID-19 Immune Atlas project, which was initiated in April 2020, aiming at providing a comprehensive overview of the immune response to SARS-CoV-2 in hospitalised patients with moderate or severe COVID-19.

The study was supported by grants from Nordstjernan AB, Knut and Alice Wallenberg Foundation, the Swedish Governmental Agency for Innovation Systems, the Swedish Research Council, the Swedish Cancer Foundation, Clas Groschinsky Foundation, the Center for Innovative Medicine at Karolinska Institutet, the Swedish Children's Cancer Foundation, Dr Åke Olsson Foundation and Karolinska Institutet's research foundation. Part of the data handling and analysis was enabled by resources provided by the Swedish National Infrastructure for Computing.

Co-author Karl-Johan Malmberg is a scientific advisor and has a research grant from Fate Therapeutics and is a member of the scientific advisory board of Vycellix Inc. Hans-Gustaf Ljunggren is a member of the board of XNK Therapeutics AB and Vycellix Inc. Jan-Inge Henter serves as consultant for Sobi AB.