Figure 3

Lung histopathology of mice infected with the recombinant viruses. Histopathology of lungs from mice infected with each PR/8 virus containing a different NS gene from a different influenza virus. Mice were inoculated intranasally with each recombinant virus at a dose of 300 EID₅₀ (in a 30 μL volume), and lung tissues were collected on day 7 following virus inoculation. Images are representative of three mice per group (A mock-infected; B PR/8 × KYG^NS—infected; C PR/8 × MI^NS—infected; and D PR/8-infected). The bar represents 100 μm. Images were obtained at 20× magnification.