[Features of pathogenesis and COVID-19 course for the elderly and old age.]

Kuznik, B I; Khavinson, V K; Smirnov, V S

The causative agents of coronavirus infection have long been considered the cause of benign respiratory diseases «common colds» until their pathogenic types appeared on the epidemic arena: SARS-CoV-1, MERS and finally, SARS-CoV-2. Diseases caused by the listed viruses characterized by moderate invasiveness and noticeable mortality compared to other respiratory viruses. The pathogenesis of these infections is based on a wide range of innate immunity dysfunctions, manifested in the direct suppression of anti-inflammatory functions and, on the contrary, the activation of pro-inflammatory functions, such as the assembly and activation of NLRP3 inflammasome, as well as the synthesis and secretion of pro-inflammatory cytokines and chemokines. Excessive secretion of pro-inflammatory factors is accompanied by a disturbance in the balance of cytokines, leading to the development of a cytokine storm. When the body manages to cope with these disorders, a stable adaptive immunity develops, which is a harmonious combination of cellular and humoral mechanisms of resistance. Particularly difficult COVID-19 occurs in elderly and senile people. It has been shown that the main tests for the risk of multiple organ failure and death in COVID-19 in this category of patients are concomitant diseases, lymphocytopenia, increased transferases, D-dimer and other metabolic disorders. It has been established that critically ill COVID-19 patients develop endothelial dysfunction, thrombotic microangiopathy, immunothrombosis and disseminated intravascular coagulation, which are the basis of multiple organ failure. Pneumonia, as a complication of COVID-19, accompanied by the development of acute respiratory respiratory syndrome, ultimately leads to pulmonary fibrosis, which is often fatal. There is no specific therapy for COVID-19. Recently, immunomodulatory drugs have been widely introduced in the treatment of this infection, including remdesivir, synthetic quinine derivatives and neutralize antibodies.