Fig. 1.
ISG15−/− mice demonstrate increased susceptibility to both influenza A and influenza B viral infection. (A and B) Lung homogenates from either ISG15+/+ or ISG15−/− mice that were mock-infected (M) or infected with influenza B/Lee (A) or influenza A rWSN (B) virus were analyzed for expression of ISG15 by Western blot analysis. (C and D) ISG15−/− (filled squares), ISG15+/+ (open squares), and IFNαβR−/− (open triangles) mice were infected with influenza B/Lee virus at 1 × 106 pfu i.n. and followed daily for weight loss (C) or lethality (D). (E and F) ISG15−/− and ISG15+/+ mice were infected with influenza A rWSN virus at either 1 × 105 pfu (E) or 1 × 104 pfu (F) i.n. and followed for lethality. The number of mice per group is indicated in parentheses and is equal for C and D.