Figure 3. Protection against challenge with H1N1 PR8.

BALB/c mice were treated with PR8-specific IgY (anti PR8 IgY) - as described in Materials & Methods at 8 hours pre- and 16, 40, and 64 hours post-infection (Pre- and post-infection treatments, Fig. 3A); at 8, 32, 56, and 80 hours post-infection (post-infection treatments, Fig. 3B); or once at 6 hours before infection (Single pre-infection treatment, Fig. 3C. Five LD₅₀ of mouse-adapted PR8 and 50 µl of IgY were used for intranasal infection and treatment, respectively. Morbidity (body weight loss) and mortality were monitored daily until recovered animals regained their initial weight. The values are the mean of 5–10 mice in each group. Mortality is expressed as % of mice that survived the lethal infection. Virus titers in the lungs (TCID₅₀) determined at day 3 after infection in mice treated with PR8 specific IgY at 6 hours before (−6 hrs) or after (+6 hrs) infection (Fig. 3D). The values are the mean of 8 mice in each group derived from 2 independent experiments. As control, a group of mice treated with mouse anti-PR8 serum (HI titer 1∶128) was included. All mice received the same amount of the IgY preparation of identical HI titer.