Fig. 6

Immunisation with M2e via Clec9A-targeted priming then conventional boosting protects mice against lethal influenza challenge. a Schematic representation of the experimental setup. BALB/c mice (n = 8–10 mice per group) were primed with 2 μg anti-Clec9A-M2e construct or the non-targeting isotype control-M2e construct, adjuvanted with 5 nmol of CpG (i.v.), then boosted 42 days later with 20 μg M2e-KLH adjuvanted with 2.5 nmol of CpG accordingly to the schedule shown. An unimmunised control group was injected with 100 μl PBS. One month (30–31 days) later they were challenged by intratracheal administration of a lethal dose (400 PFU) of H1N1/PR8 virus. b Body weight following influenza infection. Body weight was recorded daily and monitored over a period of 14 days post infection. Mice that lost 30% or more of their body weight were euthanised; by day 8 this amounted to 60% of the unimmunised group, 20% of the isotype control primed group, but none of the Clec9A-targeted primed group. Results are means with SEM of the surviving mice. Statistical analysis was performed using two-way ANOVA. (anti-Clec9A-M2e + CpG vs. Isotype control-M2e + CpG), and significance was indicated as **p < 0.01, ***p < 0.001. This result represents a single experiment, but two additional experiments gave equivalent protection results. c Lung viral titres. Lungs were harvested on days 3 and 5 post challenge with influenza virus. Influenza virus titres were determined by the plaque assay. Results represent a single experiment, initiated with n = 5 mice per group. However, one mouse of the unimmunised control group and one mouse of the isotype control group died by day 3; all targeted mice survived. Error bars represent mean with SD of surviving mice. Data were analysed by Mann–Whitney test and, significance was indicated as *p < 0.05, **p < 0.01