Fig. 6.

Efficacy of the vaccine-induced responses by the immunisation regimens. Different viral doses of IHD-J were tested on naïve mice to define the LD₅₀ (A). Six weeks after the third immunisation, six animals per group were challenged by intranasal administration with 1 × 10⁶ PFU IHD-J, and were monitored for weight (B) and survival (C). All of the animals progressively lost weight to 20% at day 4 p.c., with no relevant differences among the groups of vaccinated mice (B). From day 5 p.c., all of the animals of Group 4 (G4) started regaining weight and survived. 50% of the mice of Group 5 (G5) recovered and were protected after day 7 p.c. All of the animals of the other groups died between days 7 and 8 p.c. (C).