Изменение экспрессии Toll-подобных рецепторов, цитокинов и хемокинов в клетках слизистой оболочки ротоглотки у детей при COVID-19

Abstract

Introduction. COVID-19 is a severe respiratory disease caused by the β-coronavirus SARS-CoV-2, which is characterized by immune-mediated tissue and organ damage. It has been proven that the disease in children is relatively easy compared to adults, and the mechanisms of innate immunity play an important role in this. The aim of the investigation was to study the expression of genes encoding the innate immunity receptors TLR4, TLR7, as well as to analyze changes in the expression of proinflammatory cytokines – interleukin(IL)-1β, tumor necrosis factor (TNF)-α and interferon (IFN)-α–in children with COVID-19, depending on the severity of the disease. Material and methods. The study included 55 children with a confirmed diagnosis of COVID-19. Patient groups were formed on the basis of complaints and clinical manifestations. The 1st group of asymptomatic children included 9 people. The 2nd group included children were with a mild form of the course – 36 people, the 3rd group consisted of children with a moderate form of the course (10 people). The group of comparison consisted of 25 healthy children. RNA was isolated from the obtained material and the level of gene expression was determined by polymerase chain reaction in real time, and the level of cytokines in the supernatant was determined by the method of multiplex immunofluorescence analysis. Results. A statistically significant increase in the expression of genes for innate immunity receptors (TLR4, TLR7) in the cells of the mucous membrane of the oropharynx in children with COVID-19 has been shown. The expression of TLR4 and TLR7 was, respectively, 2.6 and 7.2 times higher in children with moderate course compared with the healthy group. At the same time, an increase in the level of expression of pro-inflammatory cytokines (IL-1β, TNFα, IFN-α) at the gene and protein levels, associated with the severity of COVID-19 was revealed. Our study also showed an increase in the production of chemokines, which correlated with the severity of the disease. Discussion. An increase in the expression level of the TLR4 and TLR7 genes by oropharyngeal mucosa cells in children with COVID-19 indicates their role in the pathogenesis of the disease. The main function of TLR4 and TLR7 is to recognize pathogen-associated molecular patterns, namely, the spike glycoprotein involved in the penetration of the virus into target cells and the single-stranded RNA of the virus. Activation of TLR4 and TLR7 leads to Toll-induced expression of genes for proinflammatory cytokines (IL-1β, TNFα, IFN-α) and chemokines, a significant increase in gene expression and protein production of which we have demonstrated. This plays a huge role in the development of the inflammatory response and indicates changes in the innate immunity of the mucous membranes in COVID-19. Conclusion. The data obtained by us can be used for further study and determination of molecular genetic markers associated with COVID-19 in children, which will allow us to select the optimal therapy option in the future.