Figure 1.

Sources of reactive oxygen species (ROS) in airway epithelial cells infected with influenza virus (IV, the left cell) or human respiratory syncytial virus (HRSV) and rhinovirus (HRV, the right cell). Cellular events, triggered by ROS production, are detailed in the text. The sources are mainly represented by nicotinamide adenine dinucleotide phosphate oxidases (NADPH oxidases, Nox), Dual oxidase (Duox) and xanthine oxidase (XO). Respiratory viruses also contribute to the production of superoxide anion by Nox2, an enzyme expressed in macrophages and, to a lesser extent, in epithelial cells.