A team from Hannover Medical School, which also includes RESIST researchers, publishes the first European study of this kind in the Lancet journal “EBioMedicine” /

The course of infection with the coronavirus SARS-CoV-2 can progress very differently – some people recover completely without symptoms or show a mild course of the disease whereas others have to be treated in hospital. However, there are also differences between patients who need to be ventilated in intensive care units and those who suffer less severely from COVID-19. A research team from the Hannover Medical School (MHH), in which RESIST researchers Professor Dr. Immo Prinz, Professor Dr. Reinhold Förster and Professor Dr. Markus Cornberg were also involved, has found out how these two groups treated in hospitals differ in their immune status. Under the leadership of the scientists of the Institute of Immunology and the Clinic for Haematology, Haemostaseology, Oncology and Stem Cell Transplantation analyzed the blood of COVID-19 patients found that a certain subset of lymphocytes, which are responsible for the adaptive immune defence, plays an important role in the course of the disease. The research work is the first European study of its kind to be published in the Lancet journal “EBioMedicine”. First author is Dr. Ivan Odak.

Number of T-lymphocytes decreases in seriously ill COVID-19 patients

“We knew that patients with severe COVID-19 disease have less lymphocytes in their blood in general,” says Dr. Christian Schultze-Florey, who, together with Professor Dr. Christian Könecke, is responsible for the study. “However, we did not know which specific subgroups was affected and to what extent.” Lymphocytes belong to the white blood cells and like all blood cells are formed in the bone marrow. After a maturation process in the body to T or B lymphocytes (cells) they are able to recognize and to eliminate foreign microbes such as bacteria or viruses. In severe cases of COVID-19 – such as patients requiring artificial respiration – all lymphocyte subtypes were found to be reduced compared to healthy controls. This was significantly less pronounced in mild COVID-19 courses.

“Another important finding was that COVID-19 patients with mild disease had more effector T-cells during hospitalization than patients with severe disease,” explains Professor Könecke. Effector T-cells are particularly activated T-cells that either directly eliminate diseased cells or generate signalling molecules to recruit other cells when mounting an immune response. The researchers also found differences in the course of COVID-19 disease. If patients recover from infection with SARS-CoV-2 and their state of health improves, the number of effector T-cells in the blood also increases significantly. Memory cells, which are a special form of T-cells that recognise pathogens during a new infection and can therefore neutralize them more effectively, can also be detected to a greater extent during recovery. If the disease does not improve, however, there is no such increase of effector cells.

More tailored diagnosis and more effective treatment possible

“The T-cell immune response seems to play a crucial role in COVID-19,” says Professor Förster, head of the Institute of Immunology and co-speaker of the Excellence Cluster RESIST. The general decrease in lymphocyte subtypes and effector T cells could therefore serve as a biomarker to assess the severity of the disease at an early stage by measuring the immune status. “This is important because some patients initially appear clinically stable when they are admitted to hospital, but a severe COVID-19 progression occurs only a short time later,” emphasizes study leader Schultze-Florey. These patients could be treated faster and more effectively by a targeted diagnosis. It might also be possible to predict the course of the therapy using T-cell markers and furthermore to control the therapy response during the treatment thereby predicting the recovery process.

The research project “Reappearance of Effector T Cells Is Associated With Recovery from COVID-19” was funded by the Corona Research Funding Programme of the State of Lower Saxony, the Cluster of Excellence RESIST and the Collaborative Research Centre (SFB) 900 of the German Research Foundation.

For further information, please contact Dr. Christian Schultze-Florey at (0511) 532-9725 or schultze-florey.christian@mh-hannover.de.

The original publication is available online at https://authors.elsevier.com/sd/article/S2352396420302607.