Assessment of formation and durability of adaptive immunity in COVID-19 convasescents

Abstract

The study of adaptive immunity in survivors of a new coronavirus infection is an important task, since there is no consensus on whether the severity of the disease affects the formation and intensity of the immune response to COVID-19. In this regard, a comparative assessment of the presence and duration of preservation of cellular and humoral immunity in patients with COVID-19 of varying severity was carried out. The study involved volunteers who had been ill with a new coronavirus infection asymptomatically (n=30), in moderate severity (n=21) and in severe form (n=12). The average age of the subjects was 47.312.5 years. The formation of cellular immunity was judged by an increase in the synthesis of IFN- in response to stimulation of lymphocytes for 16-20 hours by glycoprotein S(RBD) of the causative agent COVID-19. To determine IFN- products, the gamma InterferonIFA-BEST test system, manufactured by Vector-Best JSC, Russia, was used. The humoral immune response was recorded by detecting class G antibodies using the "SARS-CoV-2RBD-ELISA-Gamalei" test system (FSBI "N.F. Gamalei NITSEM" of the Ministry of Health of the Russian Federation). The results obtained indicate that patients from all groups have both humoral and cellular immunity to the causative agent of a new coronavirus infection. However, the number of people with adaptive immunity to COVID-19 and the duration of its preservation depends on the severity of the infection. A significant decrease in the number of people with cellular immunity was revealed in the group of seriously ill. At the same time, the majority of volunteers in this group registered the presence of class G immunoglobulins before the end of observation. In this group, unlike the other two, no patients were identified in whom only the cellular link of the immune response was activated. Volunteers who did not retain adaptive immunity to the causative agent of a new coronavirus infection appeared only by the end of the observation period. Among those who had the disease in an average form 7-8 months after recovery, there was a decrease in the number of people with cellular and humoral immunity. This process started earlier than in the group of patients who were asymptomatic and continued until the end of the study. The proportion of individuals with cellular immunity increased, and at a later date with a humoral immune response. By the end of the study, a high percentage of volunteers remained asymptomatically infected, having cellular and humoral immunity to SARS-CoV-2. Their number remained statistically higher than in the group of those who had a new coronavirus infection of moderate severity, but lower than in the group of those who were seriously ill. Also in this group, by the end of the experiment, an increase in the number of volunteers with only a cellular immune response was recorded. According to the data obtained, at the end of the observation period, the number of volunteers with humoral immunity to the causative agent of a new coronavirus infection is higher compared to those with a cellular immune response