Figure 4. rAd/NP immunization protects mice from weight loss and mortality following homologous PR8 challenge.

BALB/c mice were immunized intranasally or sublingually with 1×10⁷ PFU or 1×10⁸ PFU of rAd/NP. Control mice were immunized intranasally with rAd/Mock. Mice that received rAd/NP via sublingual route were boosted two weeks after the primary vaccination. Subsequently mice in all vaccination groups were challenged intranasally with 10 LD₅₀ of PR8 virus three weeks after their last immunization. (A) Body weight and (B) survival rate were recorded daily. (C) Viral replication levels were determined by plaque assay on MDCK cells in supernatant of lung homogenates harvested on day 5 post-challenge. Bars show log₁₀ geometric mean titer ± SEM of five mice per group.