Figure 2

Primary inoculation of rNDV-WT-VP6 induced specific immune responses against NDV and BRV-VP6 antigens. A Schematic diagram illustrating the immunization schedule and experimental group. The immunogenicity of the recombinant NDVs was evaluated in 4-week-old female BALB/c mice, which were divided into 10 groups (each n = 3, five groups for each administration route). The mice in groups 1–5 were inoculated intraperitoneally while mice in groups 6–10 were inoculated intranasally. B NDV-infected cells and C BRV-infected cells were stained using mouse sera (green) collected after primary inoculation and Hoechst 33342 (blue; nuclei). Scale bar, 50 µm. D BRV infection was performed after treatment with each dilution of antiserum. The rate of decrease from 100 FFU is shown as BRV infection inhibition ratio. E The maximum dilution ratio for complete NDV neutralization. Data represent the mean ± SEM (n = 3, *P < 0.05).