FIG 5.
Comparison of viral loads in serum samples from pigs inoculated with the WT virus and nsp1β mutants. Pigs were uninfected (mock) or infected with WT PRRSV (WT) or the three indicated mutants (vR128A, vR129A, vRR129AA). Serum samples were collected on the indicated days postinfection. (A) Viral loads in serum samples quantified by quantitative RT-PCR and calculated as viral RNA copies per milliliter. (B) Infectious virus titer in serum samples determined by a microtitration assay and calculated as log TCID50 per milliliter. Statistical significance between the wild-type virus-infected group and mutant virus-infected groups was determined by one-way ANOVA and Tukey's test and are indicated with asterisks (*, P < 0.05; **, P < 0.01; ***, P < 0.001).