mAb-PN9cx3 administration effectively reduces the viral loads in PAMs. A A total of 1 × 107 PAMs per animal were obtained from the treated piglets (JXA1/mAb-PN9cx3 and HNhx/mAb-PN9cx3) and the antibody-isotype control piglets (JXA1/mAb-2G8 and HNhx/mAb-2G8) during autopsy at 21 dpi and then harvested using the TRIzol reagent for reverse transcription. The significant differences in the results relative to those found for the PRRSV challenge groups (JXA1 and HNhx) are marked by asterisks: * (p < 0.05). B Serum samples from each animal were collected at 7, 14, and 21 dpi and subjected to an ELISA using an IDEXX HerdChek PRRS X3 ELISA kit to determine the occurrence of seroconversion after PRRSV inoculation. C Serum samples from each animal were collected at 7, 14, and 21 dpi and harvested using the TRIzol reagent for reverse transcription and qPCR analysis to determine the number of PRRSV-N gene copies in serum. No significant differences among the mAb-PN9cx3-treated groups (JXA1/mAb-PN9cx3 and HNhx/mAb-PN9cx3), antibody-isotype control groups (JXA1/mAb-2G8 and HNhx/mAb-2G8) and PRRSV-challenged groups (JXA1 and HNhx) were observed.