A blood sample is dilute. Credit: MPI Science of LightResearchers 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 take place over several months. These findings may explain why some people with COVID-19 continue to experience symptoms even after the infection has ended (long COVID).Patients still 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 when blood circulation is reduced, serious vascular occlusions may occur, and oxygen transport is restricted. 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 Center 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-cut and long-lasting changes within the cellsboth during acute infection as well as afterwards." Their results have been published in the internationally acclaimed journal Biophysical Journal.Blood samples are taken to determine the physical properties of leukocytes or erythrocytes. Credit: MPL/Guck DivisionThey used a self-developed method, called real-time cytometry (RTDC), to analyze 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 analyze up to 1000 blood cells per second. This method has two advantages: It is quick and does not require labeling the cells in a tedious process.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. They also took samples from 24 healthy individuals as a comparison group. The size and shape of red blood cells in patients with COVID-19 varied greatly from healthy individuals. 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. In COVID-19 patients, lymphocytes, a type of white blood cells that is responsible for acquired immunity defense, were significantly less flexible. This 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 to diagnose COVID-19 and even as an early warning system for future pandemics due to unknown viruses.Further information: Markta Kubnkov and colleagues, The physical phenotypes of blood cells are altered in COVID-19. Biophysical Journal (2021). Information about the Journal: Biophysical Journal Markta Kubnkov and colleagues, Physical phenotypes of blood cells are altered in COVID-19 (2021). DOI: 10.1016/j.bpj.2021.05.025
