Fig. 6.

Comparison of viral RNA loads in serum samples from pigs inoculated with the WT virus and nsp2TF/nsp2N-deficient mutants. Pigs were uninfected (mock) or infected with WT PRRSV (WT), vKO1 or vKO2 mutant. Serum samples were collected on the indicated days post-infection. Viral loads in serum samples quantified by quantitative RT-PCR and calculated as viral RNA copies per milliliter. Statistical significance between the WT virus-infected group and mutant virus-infected groups was determined by one-way ANOVA (Tukey's test) and indicated with asterisks (*, P<0.05; **, P<0.01; ***, P<0.001).