Fig. 3
Replication and pathological changes of the viruses in chickens. Groups of three chickens were inoculated orally, intranasally, and intratracheally with 106 EID50 of F/98 or the passaged viruses. a-b Replication ability of the viruses in trachea and lung of chickens were evaluated at 3 and 5 dpi. For virus titration in SPF eggs. The average of each group is shown, with error bars representing the SD. **, P < 0.01 compared with the value for the parental virus F/98 group; ##, P < 0.01 for the passaged viruses group compared each other. Data are representative of three independent experiments. c-d Histology scores of viruses in the trachea (c) and lung (d) chickens at 3 and 5 days after inoculated with H9N2 virus. Horizontal lines show the mean, error bars represent the SD, and data are representative of three independent experiments. e-l Representative H&E histology sections of the viruses at 5 d after inoculated with different virus. e-f F/98 virus-infected trachea and lung; g-h nF47 virus-infected trachea and lung; i-j vF47 virus-infected trachea and lung; k-l nF52 virus-infected trachea and lung. The histopathological changes were scored as follows. For trachea, 0: normal; 1: congestion; 2: cilia loss; 3: a few inflammatory cell infiltration; 7: a lot of inflammatory cell infiltration; for lung, 0: normal; 1: congestion; 2: hemorrhage; 3: inflammatory cell infiltration in bronchial submucosa; 7: a lot of inflammatory cell infiltration in bronchial submucosa and alveolus