Assessment of indicators of specific humoral immune against COVID-19 in children during the distribution of a new coronavirus infection in the Irkutsk region (2020–2021)

Background. There are many aspects of the development of immunity to the SARSCoV-2 virus, that remain poorly understood, like the influence of age-related characteristics on the intensity of immunity and the course of the disease. Studies of the state of immunity are widely used, mainly in the adults. But questions of the patho- and immunogenesis in children remain unsolved. Determining the nature of seroconversion of antibodies to SARS-CoV-2 in this age group is important information for serological monitoring for targeted immunoprophylaxis of the population and forecasting the epidemic situation in the region.The aim. Evaluation of the dynamics of seroprevalence of specific antibodies to SARS-CoV-2 in children of the Irkutsk region during the pandemic of a new coronavirus infection.Materials and methods. Study was conducted among the child population of the Irkutsk region in the period June 2020 – December 2021 as part of the Rospotrebnadzor project to assess population immunity to SARS-CoV-2 in the population of the Russian Federation. The content of antibodies to SARS-CoV-2 was determined by ELISA using native commercial test systems.Results. Population immunity among the child population of the Irkutsk region was characterized by an upward trend from 7.8 % at stage 1 to 98.4 % at stage 6 of the study. IgG to SARS-CoV-2 remained in 72.8 % and formed in 25.6 % of previously seronegative children. Antibodies were detected in 66.1 % of cases and persisted for up to 10–15 months after COVID-19 infection. The proportion of asymptomatic forms of infection among seropositive volunteers was 69.5 %, which determines the high intensity of the latent epidemic process.Conclusion. The level of seroprevalence was 98.4%. The current results of serological monitoring serve as a scientific basis for adjusting the list and scope of management decisions on the organization of preventive anti-epidemic measures, including vaccination

Studying Humoral Immune Response at Mild and Asymptomatic COVID-19 Forms

Background. Currently, during the COVID-19 pandemic, one of the most pressing healthcare problems is to ensure the safety of the population of the Russian Federation. There is insufficient information on the duration and intensity of post-infectious immunity in relation to SARS-CoV-2, especially in case of inapparent (without clinical signs), mild or latent forms of infection.Materials and methods. The study involved 99 volunteers with a laboratory confirmed PCR diagnosis of COVID-19 who were residents of the Irkutsk Region and of other regions of the Russian Federation and arrived to work in Bodaybo on a rotational basis. Also the study included 50 conditionally healthy people living in Irkutsk who had negative PCR results for SARS-CoV-2 RNA presence.Specific IgG and IgM antibodies to SARS-CoV-2 were detected in blood serum by enzyme-linked immunosorbent assay (ELISA) using test systems “ELISA anti-SARS-CoV-2 IgG” (FBUN SSC PMB, Obolensk, Russian Federation), “SARS-CoV-2-IgG-IFA-BEST” and “SARS-CoV-2-IgM-IFA-BEST” (Vector-Best, Novosibirsk, Russian Federation).Results. The results of a study of the humoral immunity of patients with asymptomatic and clinical forms of COVID-19 are presented. The data indicate the production of specific IgG in the blood serum of people in 2–3 weeks after SARSCov-2 infection and reaching its maximum level on the 20–21st day. The seroconversion rate  was 94.9 %. It was shown that the geometric mean titer of antibodies in asymptomatic and mild forms of coronavirus infection did not differ statistically and amounted to 1:512 and 1:632, respectively. Higher titers of antibodies (1:1600) were detected in the moderate form.Conclusion. The research results can serve as a basis for studying the dynamics of changes in the indicators  of the humoral immune response in patients with COVID-19 and for clarifying the duration of their post- infectious immunity in order to predict the development of the epidemic situation and to ensure the planning of specific prevention

Experience of Using a Complex Antigenic Preparation of the Plague Microbe to Assess the Severity of a Specific Anti-Plague Response

Background. Improving the methodology of immunological monitoring in natural foci of plague in the Russian Federation and adjacent territories to increase the effectiveness of epidemiological surveillance of plague is an urgent line of research. The lack of correlation between the production of specific antibodies to the capsular antigen (F1) ofthe plague microbe with other indicators of the state of cellular defense reactivity indicates the need to search for new informative and accessible markers for assessing anti-plague immunity.Objective: to evaluate possibility of using the complex preparation (F1 and cell membranes) evaluate the possibilities of using an artificial antigenic complex based on F1 and cell membranes (CM) of the plague microbe in antigen-specific tests in vitro in people vaccinated against plague.resu. The study involved 153 volunteers living in the territory enzootic for plague (the village of Khandagayty ofthe Ovyur kozhuun of the Tyva Republic and the village of Kosh-Agach of the Kosh-Agach district of the Altai Republic). The study included the determination of spontaneous and mitogen-induced production of cytokines (IFN-γ, IL-4, TNF-α) by blood cells, titers of specific IgG antibodies to the capsular antigen F1 of the plague microbe and concentrations ofthe main classes of immunoglobulins (IgM, IgG, IgA and IgE) in blood serum, as well as immunophenotyping of blood lymphocytes (CD3, CD4, CD8, CD16, CD19).Results. Comparative assessment of the level of cytokines (TNF-α, IFN-γ and IL-4) in spontaneous/induced F1+CM Y. pestis tests revealed a statistically significant increase in the production of cytokines TNF-α and IFN-γ in the antigeninduced tests compared with spontaneous (p < 0.01).Conclusion. Thus, the effectiveness of the use of artificial antigenic complex based on F1 and cell membranes ofthe plague microbe has been shown to assess the production of cytokines in antigen-specific cell tests in vitro, which justifies the need for further research

Population immunity to SARS-CoV-2 virus in residents of the Irkutsk Region in the dynamics of the epidemic

Background. Currently, the COVID-19 pandemic in the world and in Russia remains the main event. In this regard, the study of the manifestations of the epidemic process of the new coronavirus infection COVID-19 and the patterns of its development are an urgent area of research. In the fight against this viral disease, an important role is assigned to the study of the development of population immunity to the SARSCoV-2 virus, which will make it possible to assess the dynamics of seroprevalence and the formation of post-infectious humoral immunity, forecasting the development of the epidemiological situation, elucidating the characteristics of the epidemic process, and will also contribute to planning activities for specific and non-specific prevention of the disease.The aim: to determine the dynamics of population immunity to SARS-CoV-2 among the population of the Irkutsk region during the COVID-19 pandemic.Materials and methods. As a part of the Rospotrebnadzor project of assessing population immunity to SARS-CoV-2 in the population of the Russian Federation, the research has being conducted among the population of the Irkutsk region in the periods from June 23, 2020 to July 19, 2020 (Stage 1), from September 16, 2020 to September 25, 2020 (Stage 2), from December 7, 2020 to December 18, 2020 (Stage 3) and from March 8, 2021 to March 14, 2021(Stage 4), taking into account the reacted one recommended by the WHO. The content of antibodies to SARS-CoV-2 was determined by ELISA using a set of tests for human serum or plasma for specific immunoglobulins of class G to the proteins of the SARS-CoV-2 coronavirus.The results. The research of the humoral immunity of volunteers shows that during the period of an epidemic rise in the incidence of COVID-19 in the Irkutsk region, a low level of seroprevalence was formed (Stage 1 – 5.8 ± 0.5 %, Stage 2 – 12.1 ± 0.7 %), and in conditions of a long-term maximum increase in the incidence rate – 25.9 ± 1.0 % (Stage 3) and 46.2 ± 1.2 % (Stage 4). A significant proportion (Stage 1 – 82.2 ± 3.2 %, Stage 2 – 86.1 ± 2.3 %) of asymptomatic forms of infection characterizes the high intensity of the latently developing epidemic process in the first two stages. High levels of IgG in reconvalescents of COVID-19 persisted for an average of 3 to 5 months.Conclusion. The results of assessing the population immunity to the SARS-CoV-2 virus in the population of the Irkutsk region indicate that the seroprevalence level at Stage 4 of the research was 46.2 %. After the disease, on average, 49.5 % of persons did not detect antibodies. The results obtained should be taken into account when organizing preventive measures, including vaccination, and predicting morbidity