Secretory IgA in patients with COVID-19 at different regimens of using multicomponent vaccine Immunovac-VP-4

The mucosal immunity performs an important function in prevention of respiratory infections including COVID-19. The search for approaches to activate the synthesis of post-infectious antibodies by correcting the factors of innate and adaptive immunity at mucous membranes of respiratory tract in patients with infection caused by the new coronavirus may be relevant for the treatment of patients with COVID-19. The aim of our study was to assess the concentrations of sIgA in the upper respiratory tract in patients with a confirmed diagnosis of Coronavirus infection caused by the COVID-19, and to evaluate the effect of an immunostimulating drug of bacterial origin upon the sIgA secretion. The patients were divided into two groups: group 1 (n = 45), received basic therapy; group 2 (n = 33), in addition to basic therapy, received the bacterial vaccine Immunovac-VP-4 according to a combined scheme. The biomaterial sampling was carried out by scraping of epithelial cells from the nasal mucosa, pharyngeal scraping and salivary gland secretion on days 1, 14 and 30 of the study. sIgA levels in all biological fluids were studied using ELISA technique (JSC Vector-Best, Russia). 14 days after the start of observation, the dynamics of sIgA levels in nasal scrapings in group 1showed a significant decrease relative to the baseline values (p = 0.02), whereas the level of sIgA remained unchanged during the specified period (p = 0.07) in the group of patients receiving, along with basic therapy, additional Immunovac-VP-4 treatment. The dynamics of sIgA level in pharyngeal scrapings in the group of patients receiving only basic therapy did not change throughout the study period. Menwhile, the group of patients receiving basic therapy supplemented with Immunovac-VP-4 showed a significant increase in sIgA levels by the 30th day of follow-up over the baseline values (p = 0.02). The level of sIgA in salivary gland secretions did not differ significantly between the study groups during the entire follow-up period. The results of our study showed that, in order to assess the state of mucosal immunity in patients with COVID-19, one may recommend determination of sIgA in nasal secretions. The Immunovac-VP-4 prescribed in complex therapy is accompanied by an increase in the sIgA levels at the mucous surfaces of the respiratory tract.