In May last year, the researchers of the Center for Cell and Tissue Engineering of the International Clinical Research Center of St. Anne's University Hospital Brno (FNUSA-ICRC) and the Faculty of Medicine of Masaryk University started research of cellular immunity against COVID-19 disease. Since then, the researchers obtained blood samples from dozens of volunteers and determined the amount of memory cells that form after contact with the disease. Research will now continue - the scientists are interested in the development of patients' cellular immunity after vaccination.

The human body is equipped with several levels of defense to fight viruses including coronavirus SARS-CoV-2. The first line is mucosal immunity, which is triggered whenever it detects foreign substances on the mucosa. It is non-specific, meaning that it is not targeted to a specific type of virus or bacterium. The effectiveness of this type of immunity then depends on what viral load penetrates further into the body. In the next phase, non-specific immunity becomes specific precisely because T-lymphocytes begin their reproduction based on the specific protein that the virus manifests. "T-lymphocytes can be thought of as cells that carry various locks. Their task is to look for the pathogen on the surface of the pathogen cells - for example, the virus, into which they will fit. If the T lymphocyte - ie the lock - is unlocked by the key of the virus or another pathogen, a number of processes are started, which lead to the elimination of the infection in the body, "described doc. RNDr. Irena Koutná, Ph.D., Head of the Center for Cell and Tissue Engineering Research team FNUSA-ICRC and scientist of the Medical Faculty of Masaryk University.

Described research focuses on the number of these special cells. The researchers exposed the blood samples to the SARS-CoV-2 virus and used a flow cytometer to determine the number of memory cells. "These cells are formed by the body only after contact with the disease. Memory cells then respond in a test tube to virus pieces by producing specific interferon. Thanks to that, we will measure how many such cells a person has, "said Irena Koutná. The research results so far show that the variability of the memory trace among people who have suffered from the disease is very wide and individual, so it does not matter whether the patient had a mild or severe course of the disease. Importantly, it persists for longer than antibodies to COVID-19, which are almost undetectable after three months. "We also detected memory cells in patients nine months after the disease," emphasized doc. Irena Koutná. Memory cells generally cannot guarantee that an individual will not be infected with the same disease again. However, their amount determines how quickly the organism copes with the same infection.

Cellular immunity research now in the International Clinical Research Center of the University Hospital at St. Anny in Brno continues, the researchers focused on vaccinated patients.

The first phase of the study will be accurately evaluated in mid-March, but preliminary data are already available, which show quite convincingly that one dose of vaccination is definitely not enough. "After the first dose, most developed either an undetectable or very weak memory trace. Four weeks after the second dose, the vaccinees developed a memory trace comparable to the immunity induced by the disease. It is also important to adhere to a three-week vaccination "window" in order to build up immunity. However, it should be noted that many patients had a higher value of the memory trace after the disease. However, based on preliminary data, it can be concluded that vaccination will protect vaccinated individuals for at least half a year and perhaps even a year. Therefore, revaccination may be necessary within the first year of the first application. The study will continue, we will test the vaccinated even after half a year and in longer time series, "added doc. Irena Koutná.

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