Etiological Group Analysis of Cytokine Response To Influenza-Like Illnesses

Respiratory infections, collectively, are one of the worlds most common and serious illness groups. As recent observations have shown, the most severe courses of acute respiratory infection, often leading to death, are due to uncontrolled cytokine production (hypercytokinemia). The research presented is devoted to assessment of mRNA expression of specific cytokines (IL-1b, IL-2, IL-4, IL-6, IL-8, IL-10, IL-18, TNF-, IFN-{lambda}) and MxA in whole blood leukocytes, by means of real-time PCR. This study involved 364 patients with respiratory illness being treated in clinics in St. Petersburg (Russia) in 2018-2019 and 30 healthy subjects. In 70% of patients, bacterial or viral pathogens were identified, with influenza viral infections (types A, B) prevailing. Cytokine analysis was carried out in the acute phase of illness (2-3 days from onset of initial symptoms) and in the stage of recovery (days 9-10). Significant increases in the expression of IL-18, TNF, and IL-10 were observed, relative to controls, only with influenza viral infections. We have shown a difference in IL-6 mRNA expression in patients with bacterial or viral pathogens. No significant difference was found in WBC IL-4 expression levels between patients and healthy subjects. Investigation of the nuances of systemic cytokine production, in response to specific viral and bacterial pathogens, makes it possible to: assess the risks of developing hypercytokinemia during respiratory infection with agents circulating in the human population; and to predict the pathogenicity and virulence of circulating threats.