Mechanism of mucosal defence and options to reduce virus invasion during the COVID pandemic

László, H.

The portal of entry for coronavirus is the mucous membrane of the respiratory tract. Severity, organ manifestations and outcome of COVID-19 are determined by the viral load, burdening the attacked organism. Condition of the respiratory tract and gastrointestinal mucosa and the capacity of their defence system are crucial for virus penetration, fusion with epithelial cells and replication. Direct neural spread, penetration into the deeper airways and spread through the lymph nodes depend on these functions. Virus binding and engulfment is an active process. The virus penetrates the endosomes of the epithelial cell, by enzymatic transfer where it is recognised by natural defence agents and triggers the first defence responses. These alarm the entire immune system and trigger a whole chain of inflammatory and enzymatic defence processes (cytokine and bradykinin storm) proportional to the viral load. The severity endpoint of COVID-19 pathology is alveolitis, cerebral vasculitis and intestinal damage, often with fatal outcome. The airway mucosa defends itself by secreting surface factors and recruiting and activating cells of the adaptive immune system. An important element of the latter is the early appearance of secretory IgA in the mucosa. The viral invasion can be prevented by application of a nasal spray containing carrageenan, which engages the virus and prevents its attachment by the gel-forming property of carrageenan. This effect has worked in previous virus epidemics and the first COVID-19 experiences confirm its protective role. © 2021 Literatura Medica Publishing House. All rights reserved.