Fig. 7

The effect of exchange of SP and nsp2 on induction of humoral immunity. A The serum antibody dynamics from infected piglets by an IDEXX HerdChek PRRS X3 ELISA kit. S/P ≥ 0.4 was considered seropositive. B The serum NA titer at 42 DPI titrated in MARC-145 cells. C The serum NA titer at 63 DPI titrated in MARC-145 cells. Error bars represent standard deviation (SD). Asterisks mean the statistical difference between infected groups (*, P < 0.05; **, P < 0.01; ***, P < 0.001)