FIG 4.

Efficacy of passive serum transfer. (A) Schematic overview of the experimental design. Mice were vaccinated on days 0 and 28 with the respective VSV*ΔG replicons, and serum was isolated 7 days after the boost immunization. Sera were subsequently transferred into naive mice. Blood samples were taken 24 h later, and animals were challenged with 1 × 10⁴ TCID₅₀ of H1N1 PR8. (B) Total antibody responses against PR8 and NI titers of donor mice. Bars represent the means for three repeated measurements of pooled serum, and error bars indicate the standard deviations of the means. Log₂-transformed groups were compared to the NA_PR8 group using one-way ANOVA with a Tukey posttest. Statistical significance is indicated (*, P < 0.05; ****, P < 0.0001). (C and D) Percent weight change (C) and percent survival (D) in recipient mice. Upon challenge, body weight was monitored as a measure of morbidity. Animals were euthanized as soon as the weight loss reached 25%.