Expression of pro-inflammatory cytokines (IL-18, IL-33) at the level of the mucous membrane, the entry point of infection, in persons who have experienced COVID-19 disease

Abstract

Introduction. The mucous membrane of the upper respiratory tract is the entrance gate for a large number of infections, including the SARS-CoV-2 virus. That is why the main task of the immune system of the mucous membranes of the entrance gate of infection is to maintain respiratory function. High production of proinflammatory cytokines, which play a key role in the development of severe COVID-19 infection, leads to detrimental consequences for all body systems. Their long-term influence can not only aggravate chronic pathologies, but also significantly increase the recovery period, leading to a decrease in the quality of life of patients. Therefore, the purpose of this work is to study the expression of IL-18 and IL-33 genes at the level of the mucous membranes of the upper respiratory tract in patients who have had COVID-19 disease. Materials and methods. The present study involved patients who had moderate or severe COVID-19. The control group consisted of relatively healthy individuals. The expression levels of IL-18 and IL-33 were detected using RT-PCR. Results. During the entire period of rehabilitation after suffering from COVID-19, patients showed a tendency to increase the level of IL-18 expression at the level of the mucous membranes of the nasopharynx and oropharynx. The level of IL-33 production was also increased, but varied depending on the location and period of sample collection. Conclusion. This increase in the level of IL-18 during the rehabilitation period of patients after COVID-19 may be explained by the fact that the virus, by activating glia through olfactory receptor neurons, triggers a powerful immune response and promotes the production of a large number of pro-inflammatory cytokines. On the contrary, overexpression of IL-33 in the late stages of rehabilitation is most likely associated with its ability to restore barrier tissues of the mucous membranes of the upper respiratory tract. Thus, we can conclude that the virus promotes excessive production of pro-inflammatory cytokines, the amount of which increases maximally at the 6th month of rehabilitation after suffering from COVID-19.