Figure 2: Oseltamivir resistance in a recombinantly derived H7N9 virus does not modulate viral pathogenicity in mice.

Female BALB/c mice (6–8-week-old) were infected intranasally with various amounts of rSH/1 (squares) or rSH/1:AH/1-NA (triangles) viruses. (a) Viral replication in lung, spleen and intestine. Mice (n=9) were infected intranasally with 100 PFU of rSH/1 (squares) or rSH/1:AH/1-NA (triangles) viruses. On days 2, 4 and 6 post infection, three mice per group were euthanized. The presence of virus in lung, spleen and intestinal tissues was determined by standard plaque assay on MDCK cells. Dashed line indicates the limit of detection (100 PFU ml⁻¹). ND=not detected. (b–e) Weight loss of mice after infection with rSH/1 (squares) or rSH/1:AH/1-NA (triangles) viruses. Mice (n=5) were infected intranasally with serial 10-fold dilutions of each virus, from 10⁴ to 10¹ PFU per mouse. The mock animals (circles) were inoculated with PBS/BSA. Following infection, mice were weighed daily, and the average body weights±s.d. of surviving animals in each group up to day 14 post infection are indicated as percentages of the original body weights. Dashed line indicates 75% of initial body weight. (f–i) Survival of mice after infection with rSH/1 (squares) or rSH/1:AH/1-NA (triangles) viruses or mock treated (circles). Kaplan–Meier curves represent survival after infection with each virus at 10-fold dilutions from 10⁴ to 10¹ PFU or mock infection with PBS/BSA (n=5 per group). Please note that experiments b–e and f–i share the same control mock-infected animals. Error bars represent s.d. in all panels.