FIG. 2.

Human cross-reactive 2009 pandemic H1N1-neutralizing antibodies are functional in vivo. Human serum pools with (H1 pos) or without (H1 neg) a detectable cross-reactive 2009 pandemic H1N1 (A/California/4/2009)-neutralizing antibody titer were injected intraperitoneally 24 h prior to intranasal lethal challenge. Control mice were injected with PBS or convalescent-phase serum obtained from 2009 pandemic H1N1 virus-infected ferrets. Survival was monitored for 21 days, and weight loss was monitored for 16 days. Data shown in panel A are the cumulative results of two experiments, and those in panel B represent the average weight loss of one indicative experiment. (A) ***, P < 0.001 compared to results for other groups; **, P < 0.01 compared to results for PBS control group and P < 0.05 compared to results for H1-negative group; *, P < 0.01 compared to results for PBS control group. (B) *, P < 0.01 compared to results for other groups..