Quantification of anti-PRRSV antibodies (IgG) and VNA titers measured in PRRSV-infected pigs. A Anti-PRRSV antibody (IgG) response was measured in serum samples collected weekly until 28 dpc using a nucleocapsid (N) protein-based ELISA kit based on the manufacturer’s instructions, and the result is expressed as the S/P ratio. An S/P ratio ≥ 0.4 is considered positive for PRRSV-specific antibodies (IgG). B The levels of the VNA titers were measured using a fluorescent focus neutralization (FFN) assay. The error bars represent the SEM. Asterisks indicate significant differences in the level of anti-PRRSV IgG among the genotypes (*p < 0.05).