Figure 5. Epitope-driven vaccine reduces lung viral titers in pandemic H1N1 influenza infection of HLA DR3 transgenic mice. Mice that were primed with plasmid DNA vaccine and boosted with peptides comprising cross-conserved H1N1 influenza class II HLA epitopes or vaccine vehicle containing no epitopes were infected with 10⁶ PFU A/California/07/2009. Data are the viral burden of four mice from each group at two and four days post-infection as determined by viral plaque assay. Individual titers are denoted by filled dots and average titers by horizontal lines. Titers in vaccinated mice showing statistical significance (Student t-test) when compared with controls are indicated: **p < 0.01