Pathomechanisms of Viral Infections in the Respiratory Tract and Possibilities of Intervention

Abstract

Viral pathogens responsible for infections of the respiratory tract, such as influenza, bird flu, swine flu, but also coronavirus are not primarily cytopathogenic. This means that they don´t destroy the infected epithelial cell but reprogram the metabolism of infected epithelial cells so that the epithelial cells produce and excrete thousands of copies of the virus. If the viruses would destroy the cell, there would no copies. Some of these epithelial cells eventually die from exhaustion, the majority of these virus-infected epithelial cells have to be eliminated by the body's own defence mechanisms e.g. macrophages, killer lymphocytes etc. This requires an increase of permeability of the  capillary bed in which - mediated by proinflammatory cytokines (LOX, COX, PGE2, LTB4, Il2 ) - the capillary bed becomes more permeable so these effector cells can reach the infected epithelial cells from the blood stream. Proinflammatory cytokines are also responsible for the symptoms of a viral infection such as fever, fatigue, joint pain, etc.