Severe Covid-19 diseases can take very different courses. Still, there seem to be some commonalities in the immune response. According to a new study, the recovery process can primarily be seen from a certain blood value.
COVID-19 can affect many organs and take very different courses. However, the course of the disease largely depends on the immune response. Since this reaction is reflected in the blood, a team from the German Center for Neurodegenerative Diseases (DZNE) looked for similarities. To do this, the DZNE scientists repeatedly examined the blood of 139 Covid-19 patients who had to be treated in intensive care. The patients were between 21 and 86 years old, most were male. 105 recovered sufficiently to be discharged from the ICU, and 34 patients died.
Neutrophil count decreases during recovery
The analyzes revealed that recovery from severe COVID-19 is characterized by the gradual decline in certain white blood cells: neutrophils. They are the most common white blood cell and act as one of the first lines of defense against pathogens in the immune system’s arsenal. “We found that patients with severe COVID-19 have a high number of mature, i.e. fully developed, neutrophils in their blood, the amount of which decreases during the recovery process,” says first author Dr. Amit Frischberg.
The levels of other white blood cells also changed over time, with some going down while others going up. “However, these changes are less pronounced than in neutrophils,” says Frishberg.
Increase associated with poor prognosis
But the researchers were also able to observe the opposite case: an increase in mature neutrophils over a longer period of time leads to a high probability of death in intensive care patients. “This may be due to the fact that the steady increase is accompanied by an excessive and therefore harmful immune response,” says Frishberg.
The researchers also discovered other changes during recovery that affect molecular signaling pathways and regulatory mechanisms of the immune system. “What is remarkable about our results is that recovery in all patients followed the same biological pattern, despite individual differences in the time course of the disease. So there is a common thread, so to speak. We found no evidence in our data that the recovery process after severe COVID-19 disease can follow different pathways,” emphasizes Frishberg.
Biomarkers for prognosis
Based on the results, the authors now propose to use the number of neutrophils in the blood as a biomarker for the prognosis of severe Covid-19.
For their analysis, the scientists primarily relied on transcriptomes of the blood. These data sets reflect the gene activity of all blood cells at a given point in time. As a rule, more than 10,000 different genes are recorded. Blood transcriptomes provide a very detailed picture of the immunological process. This very complex data was analyzed using computer-aided methods.