AIV replicates in mouse intestinal organoids. Replication of H9N2 virus (106 EID50) in mouse intestinal organoids. A–D GAPDH-normalized mRNA transcript levels of H9N2 HA, NA, NP and PB1 RNA are shown as fold-increases relative to those at 1 h post-infection. E Virus was evaluated by immunofluorescence staining for nonstructural protein NP (green) and structural protein HA (red), and DAPI (4,6-diamidino-2-phenylindole) to stain the nucleus (blue). Mean values ± SE of triplicate assays are shown; *P < 0.05; **P < 0.01. Experiments were performed in triplicate. Bars: 25 μm (E).