Figure 1.

Survival rates (A) and body weight changes (B) after challenge with lethal homologous influenza virus. One hundred and fourteen mice were randomly divided into six groups. Group D1 received one dose of 100 μg NP DNA vaccine; group P1 received one dose of 50 μg rNP vaccine; group D2 received two doses of 100 μg NP DNA vaccine; group D1P1 received one dose of 100 μg NP DNA vaccine followed by one dose of 50 μg rNP; group D2P1 received two doses of NP DNA vaccine followed by one dose of rNP vaccine. 3 weeks after the last immunization, mice were challenged with a lethal dose (5×LD₅₀) of influenza PR8 virus. Survival rates (A) and body weight loss (B) were monitored for 21 days.