Fig. 4
IgM-adjuvanted inactivated PRRSV vaccine enhanced the secretion of IFN-γ after heterologous HP-PRRSV challenge. A. After HP-PRRSV challenge, serum samples were collected at the indicated time points to examine serum IFN-γ levels using ELISA. All experiments were repeated at least three times for each serum sample. B. Peripheral blood mononuclear cells (PBMCs) were isolated from surviving piglets at the end of the experiment. Next, 1 × 104 PBMCs were stimulated with 1 μg of recombinant PRRSV N proteins for 48 h. IFN-γ-producing cells were analysed by porcine IFN-γ ELISpot. PBMCs obtained from the mock piglets were treated with ConA or left untreated as positive and negative controls for the assay. The represented dot images were selected, and the numbers of dots for surviving piglets were recorded using an EliSPot reader. Data are expressed as the mean ± SD and were subjected to Student’s t test. Significant differences between the indicated groups are marked by “*” (p < 0.05), whereas “ns” means not significant.