Possible role of reactive oxygen species in antiviral defense.

The role of reactive oxygen species (ROS) participating in antiviral host defense is considered. Unlike antibacterial defense, when ROS and their derivatives act as biological weapons killing pathogenic bacteria, the function of ROS in the antiviral defense is assumed to be mediated by apoptosis. It is suggested that a cell activates generation of superoxide and hydrogen peroxide by xanthine oxidase as well as by intracellular NADPH-oxidase in response to appearance of a virus in its cytoplasm. Increase in ROS level turns on the process of programmed cell death in the infected cells. Moreover, H2O2 diffuses into the adjacent cells (due to its high membrane permeability), also inducing apoptosis (death of bystander cells). So, the infected cell and its neighbors (which are the most likely to be infected) are eliminated, thus blocking the spreading of the viral infection.