Figure 4
DTMUV N7-MTase mutants immunization protects ducks from death after challenge. A Scheme of challenge of SPF duck. 5-day-old SPF ducklings were immunized with 200 µL 104.75 FFU/mL WT, K61A, K182A, E218A, while the WF100 vaccine and DMEM were used as positive and mock control, respectively. At 14 dpi, animals were challenged with a high lethal dose of 106 FFU WT DTMUV, then clinical signs of disease, body weight change and survival were monitored. B Clinical symptom scores (n = 7). The data are presented as the means ± SDs. *p < 0.05 (one-way ANOVA). C Body weight change (n = 3). Means with SD are shown. D Survival 16 days after challenge (n = 7). The statistical significance of survival was analyzed using a survival curve and the log-rank (Mantel–Cox) test. E Viral loads in sera were measured by RT-qPCR at 4 days post-challenge. Each of these was conducted with three parallel replicates. Bars show means ± SDs. ND, Not detected (one-way ANOVA). F Spleen histological changes of ducks. The black arrow indicates splenic lymphocytes were degenerated, necrotic, and vacuolated. Scale bar, 100 μm.