Cytokines in acute respiratory viral infections

Human Respiratory syncytial virus (hRSV) and human metapneumovirus (hMPV) are the two major etiological viral agents of lower respiratory tract infections, affecting mainly infants, pediatric patients and the elderly. Although the infection by either of the viruses trigger an antiviral immune response that mediate viral clearance and disease resolution in immunocompetent individuals, the promotion of long-term immunity appears to be deficient and reinfection are common throughout life. Coronaviruses (CoVs) comprise a polymorphic group of respiratory viruses causing acute inflammatory diseases in human animals. Until recently, this infection in humans was mainly observed during the autumn-winter period and characterized by a mild, often asymptomatic, course. The situation changed dramatically in 2003, when SARS outbreak caused by pathogenic CoV (SARS-CoV) was recorded in China. A decade later, a new CoV outbreak occurred in the form of the Middle East respiratory syndrome (MERS-CoV), whereas in December 2019, SARS-CoV-2 (COVID-19) cases were recorded, which transformed within the first months of 2020 into the pandemic. Such events were accompanied by production of pro-inflammatory cytokines, with the magnitude elevating up to the state of cytokine storm.