Dynamics of specific humoral response in COVID-19 patients

Introduction. The pandemic caused by the SARS-CoV-2 virus is an important medical and social problem. It remains unclear the stability of the developed humoral immunity against the SARS-CoV-2 virus, the average duration of preservation of the titer of specific antibodies. The need to identify humoral mechanisms of immune defense in patients with COVID-19 determined the purpose of this study. The aim of the study – to evaluate the dynamics of changes in the content of specific IgG antibodies against various antigens of the SARS-CoV-2 virus and B-lymphocyte subpopulations throughout the year in people who have had COVID-19. Material and methods. The study included 90 patients who had undergone COVID-19 in various forms, subsequently divided into 2 groups: persons with asymptomatic and mild course (57 patients) and with moderate or severe course of the disease (33 patients). The dynamics of the concentration of specific antibodies to the SARS-CoV-2 virus was evaluated by enzyme immunoassay every 3 months for a year. The content of the total pool B-lymphocytes (naive B-lymphocytes, memory B-cells, regulatory B-lymphocytes) and various subpopulations was evaluated by flow cytofluorimetry. Results. When assessing the dynamics of IgG to the S-protein of the SARS-CoV-2 virus, their preservation was noted by the 12th month after recovery. In patients with severe and moderate COVID-19 forms, these indicators are significantly higher. More severe forms of COVID-19 are accompanied by significantly higher content level of memory B cells throughout the observation period. Conclusion. Moderate and severe forms of COVID-19 induce more persistent postinfectious humoral immunity, provided by an increase in memory B cells in comparison with lighter forms.