Protection against flu virus challenge in mice immunized by A/PR8 mutants.

<p>A. Body weight loss in vaccinated/challenged C57/B6 mice. Mice were vaccinated with Pol1, Pol2, A/PR8 or mock vaccinated and challenged intraperitoneally on day 21 post-immunization with a lethal dose of A/PR8 (1×10⁷ pfu ). Body weight was monitored daily. B. Survival rate of mice immunized by Pol1, Pol2, A/PR8 against lethal dosage challenge.