Figure 10. Oral vaccination with recombinant L. plantarum protects mice from homologous and heterologous influenza virus infections.

Groups of C57BL/6 mice were immunized and challenged as indicated in (a). Four weeks after vaccination, the mice were infected with either mouse-adapted H9N2 AIVs (10 × LD₅₀) or A/PR/8/34(H1N1) (0.5 × LD₅₀), and their weight loss (b,d) and survival (c,e) were recorded for 14 days. The weight loss and mortality data are presented as the means ± SEM of triplicate tests (n = 10 mice per group). The weight loss data were analysed by using an unpaired t-test. The mortality data were analysed by using a Log-rank (Mantel-Cox) test and are expressed relative to the NC8-pSIP409-NP-M1-Ctrlpep group (*P < 0.05). Five days after infection, the mouse-adapted H9N2 AIVs (f) and A/PR/8/34(H1N1) (g) in the lungs were titrated in MDCK cells. The results are presented as the means ± SEM of triplicate tests (n = 5 mice per group) and were analysed by using a one-way ANOVA, assuming a Gaussian distribution, followed by Dunnett’s post-test and are expressed relative to the PBS, NC8-pSIP409 and NC8-pSIP409-NP-M1-Ctrlpep and the H9N2 inactivated vaccine groups, (*P < 0.05, **P < 0.01, and ***P < 0.001). The data shown represent one of three experiments with equivalent results.