The induction of pattern-recognition receptor expression against influenza a virus through Duox2-derived reactive oxygen species in nasal mucosa

Westudied the relative roles ofDuox2-derived reactive oxygen species (ROS) in host defense against influenza A virus (IAV) infection in normal human nasal epithelial cells and mouse nasal mucosa.We found thatDuox2 primarily generatedROS rapidly after IAVinfection in normal human nasal epithelial cells and that knockdown of Duox2 aggravated IAV infection. In addition, Duox2-derived ROS enhancement significantly suppressed IAV infection in nasal epithelium. In particular, Duox2-derived ROS were required for the induction of retinoic acid-inducible gene (RIG)-I and melanoma differentiation-associated protein 5 (MDA5) transcription. After intranasal IAV inoculation into mice, viral infection was significantly aggravated from 3 days postinoculation (dpi) in the nasal mucosa, and the IAVviral titer was highest at 7 dpi.BothRIG-I andMDA5messenger RNA levels increased dominantly in mouse nasal mucosa from 3 dpi; consistent with this, RIG-I and MDA5 proteins were also induced after IAV infection. RIG-I and MDA5 messenger RNA levels were induced to a lower extent in the nasal mucosa of the mice that were inoculated with Duox2 short hairpin RNA, and the IAV viral titer was significantly higher in nasal lavage. Taken together, Duox2-derived ROS are necessary for the innate immune response and trigger the induction of RIG-I andMDA5to resist IAV infection in human nasal epithelium and mouse nasal mucosa.