SARS-CoV-2: T-cell immunity plays important role in virus defence
Research group investigates immune response in blood samples of COVID-19 sufferers and recovered patients
How severely we actually contract COVID-19 after infection with SARS-Cov-2 depends on our immune system. Antibodies, which are supposed to prevent the viruses from entering the cell as a so-called humoral immune response, are decisively involved. The concentration of these protein compounds decreases over time - especially in patients who have only had a mild course of the disease. But our immune system knows another way to fight viruses: the cellular immune response with the help of T-lymphocytes. They belong to the white blood cells and seek out cells affected by the virus in order to destroy them and thus prevent further virus spread in the body. A research team led by Professor Dr. Rainer Blasczyk, Director of the Institute of Transfusion Medicine and Transplant Engineering at the Hannover Medical School (MHH), and Professor Dr. Britta Eiz-Vesper has investigated precisely this aspect of the virus defence and proved that T-cell immunity plays an important role in lasting protection against SARS-CoV-2. The study in cooperation with the University Hospital Essen has now been published in the renowned journal "Immunity". First author is Dr. Agnes Bonifacius.
Concentration of immune cells remains largely stable
"Until now, there was a lack of data on cellular immunity against SARS-CoV-2 during the disease and beyond," says Professor Blasczyk. The scientists therefore analysed blood samples from COVID-19-genese patients with those from acutely ill and healthy, non-infected (SARS-CoV-2-seronegative) control groups and compared both the antibody level and the concentration of T-lymphocytes. They found that those who had recovered did not have as many antibodies in their blood as those who were immediately ill. However, the scientists were able to detect a high number of memory T effector cells specialised in SARS-CoV-2. These not only recognise the crown-like spike protein, but also other structures of the virus surface. As immunological memory, they also improve protection in the event of renewed infection with the same pathogen. "Apparently, T-cell immunity remains unchanged after COVID-19, although the antibody concentration drops sharply," the transfusion physician notes.
"Apparently, T-cell immunity remains unchanged after COVID-19, although the antibody concentration drops sharply," the transfusion physician concludes.
Earlier contact with harmless coronaviruses protects
Contact with other members of the coronavirus family, which cause harmless flu infections, for example, apparently also has a favourable effect on the SARS-CoV-2 defence. "An existing immunity against such endemic coronaviruses has a positive effect on the development of T-cell immunity against SARS-CoV-2 and thus presumably also on the course of COVID-19," explains Professor Eiz-Vesper. This cross-immunity is particularly interesting with regard to virus mutations. "If it already helps against a more distantly related coronavirus, the effect could be much greater with the SARS-CoV-2 variants, which are much more similar to each other," the scientist suspects.
This question will now be clarified in a next study. In addition, the scientists want to investigate whether T cells could also be used therapeutically for certain moderately severely ill patients with COVID-19. -n. Similar to the treatment with the blood plasma of convalescents, in which the administration of antibodies against SARS-CoV-2 is supposed to prevent severe disease progression, donated T cells could also help against COVID-19. "In certain patients, we see a lack of their own T cells or observe that the defence cells are less active," explains the immunologist. The results could then not only help to better predict disease progression, but also lead to more successful vaccination strategies.
The study was conducted in cooperation with the University Hospital Essen, the German Centre for Infection Research (DZIF), the Centre for Individualised Infection Medicine (CiiM), the MHH Clinic for Gastroenterology, Hepatology and Endocrinology, the MHH Clinic for Pneumology, the MHH Clinic for Renal and Hypertension Diseases, the MHH Clinic for Paediatric Haematology and Oncology and the Hannover Public Health Department.
For further information, please contact Professor Dr Rainer Blasczyk, firstname.lastname@example.org, phone (0511) 532-6700 and Professor Dr Britta Eiz-Vesper, email@example.com, phone (02511) 532-9715.
The original paper "COVID-19 immune signatures reveal stable antiviral T cell function despite declining humoral responses" can be found here: https://pubmed.ncbi.nlm.nih.gov/33567252/