FIG 5.

Anti-NA antibody response elicited by swap virus vaccination protects from matched NA influenza virus challenge. (A) Equal amounts of sera isolated from immunized mice were pooled within each group. Pooled sera were passively transferred intraperitoneally to 5 naive mice per group. Two hours posttransfer, mice were infected with five times the median lethal dose (LD₅₀) of a recombinant PR8 virus expressing PR8 HA and HK14 NA. (B and C) Weight loss and survival were measured following infection. Mice that lost >75% of their body weight were euthanized.