Survival rate and lung virus titer in response to immunization and lethal viral challenge in mice fed diets with adequate protein (AP) or very low protein (VLP). A, AP (left) and VLP (right) groups of mice receiving HA, adjuvanted HA, or adjuvant alone were assessed for protection from lethal (rgH5N1) viral challenge. Survival rates for AP and VLP groups are shown; data represent results from 2 independent experiments. B, Lung tissues harvested from mice on the AP or VLP diets at day 4 after viral challenge were homogenized and assayed for virus titer, as described in Materials and Methods. Data represent means and standard deviations from 2 independent experiments. The differences in survival percentage by treatment were statistically significant, as follows: AP groups: 3 μg of H5 (A/Vietnam/1203/2004/H5N1)-HA (hemagglutinin) vs adjuvant, P < .01; 10 μg of H5-HA vs adjuvant, P < .05; 3 μg of H5-HA plus adjuvant vs adjuvant alone, P < .001. VLP groups: 3 μg of H5-HA plus adjuvant vs adjuvant alone, 3 μg of H5-HA vs 3 μg H5-HA plus adjuvant, and 10 μg of H5-HA vs 3 μg of H5-HA plus adjuvant, all P < .001. Abbreviation: EID50, egg infectious dose50.