Researchers at Max-Planck-Zentrum fr Physik und Medizin Erlangen were able, for the first-time, to demonstrate that Covid-19 has a significant effect on the size and stiffness red and white blood cells. This can sometimes last several months. These findings may explain why some people with long-term Covid symptoms continue to have symptoms even after the infection has ended.Some patients continue to experience shortness of breath, fatigue, and headaches after six months of severe SARS-CoV-2 infection. The post Covid-19 syndrome (also known as long covid) is not fully understood. It is evident that blood circulation can be impaired and dangerous vascular occlusions may occur. Oxygen transport is also limited. All of these phenomena are caused by the role that blood cells and their physical properties have in these conditions.This aspect was investigated by a team of scientists headed by Jochen Guck, Markta Kubnkov and Martin Krter, all from the Max-Planck-Zentrum fr Physik und Medizin. The Max Planck Institute for the Science of Light, the Friedrich Alexander University Erlangen-Nuremberg, and the German Centre for Immunotherapy, measured the mechanical state of white and red blood cells. Professor Guck, who is currently the MPL managing director, reports that "we were able to detect clear changes in cells -- both during acute infection and afterwards." Their results have been published in Biophysical Journal by the research group.They used a self-developed method, called real-time cytometry (RTDC), to analyse blood cells. This was recently recognized with the prestigious Medical Valley Award. The researchers use this method to send blood cells through a narrow channel at high speeds. The process causes the leukocytes to stretch and the erythrocytes to contract. Each cell is recorded by a high-speed camera through a microscope. Custom software then determines the type of cells present and their size and shape. It is possible to analyse up to 1000 blood cells per second. This method has two advantages: It is fast and does not require labelling.This method could be used to help detect potential pandemics caused by unknown viruses in the future.Erlangen biophysicists examined over four million blood cells taken from 17 patients with Covid-19 who were acutely ill. They also took samples from 24 healthy individuals as a comparison group. The size and shape of red blood cells in patients with the disease differed from healthy individuals, they found. This could indicate damage to these cells, which could explain the higher risk of embolisms and vascular occlusion in the lungs. Infected people may also have a reduced oxygen supply, which is one the most important tasks of the erythrocytes. Covid-19 patients had significantly less lymphocytes, which is one type of white blood cells that are responsible for acquired immunity defense. This usually indicates an immune response. Similar observations were made for neutrophils granulocytes (another type of white blood cell involved in the innate immune reaction). These cells remained significantly altered for seven months after acute infection.Marketa Kubnkov is the first author of this research article. "We suspect the cytoskeleton, which is largely responsible to cell function has changed," she says. She believes that real-time deformability and cytometry can be used regularly to diagnose Covid-19, and even as an early warning system for future pandemics due to unknown viruses.
