PPIA and infection: We further performed histopathological examination of lung, nasal turbinate, and trachea tissues at day 2, 5 and 7 post infection and found that SeV-infected Ppia−/− mice displayed severe bronchopneumonia, interstitial pneumonia, congestion in blood vessels, and dropout of the mucous epithelium, whereas SeV-infected WT mice only displayed slight bronchopneumonia and congestion in blood vessels during the infection (Figure 2D, Figure 2—figure supplement 1A,B).