Fig. 4

The SP region alone is sufficient to provide homologous immunity. A Protocol of the animal trial. B The rectal temperature curves of piglets. C Clinical mental state scores of piglets of different groups following challenge. The total clinical scores for each piglet were the sum of gross clinical score (GCS), respiratory clinical score (RCS), and nervous signs score (NSS). D The weight curves of piglets after immunization. The starting point of DPI was on the first day after immunization. All piglets were challenged with JXwn06 at 42 DPI. Error bars represent standard deviation (SD). Asterisks mean the statistical difference (*, P < 0.05; **, P < 0.01; ***, P < 0.001)