Fig. 3.

Immunization with LAH-KLH protects mice in vivo. Two weeks after secondary immunization, mice were challenged with 4 × 10⁵ pfu of X31, a mouse-adapted H3 influenza virus (A and B), 500 pfu (10–15 MLD₅₀) of the mouse-adapted H1 virus PR8 (C and D), or 500 pfu of an H5 highly pathogenic avian influenza virus modified to remove the polybasic cleavage site in the viral hemagglutinin (HAlo virus) (12) (E and F). n = five BALB/c mice per group. Because of differences in pathogenicity, survival was defined as 20% weight loss for X31 (H3) and PR8 (H1) viruses and 30% weight loss for VN/2004 (H5) virus.