mAb-PN9cx3 administration alleviates the lung pathological lesions observed after PRRSV challenge in vivo. A A total of 28 piglets were randomly divided into seven groups (n = 4): one group served as the negative control (MOCK) group, the JXA1 and HNhx groups were challenged with HP-PRRSV-JXA1 and NADC30-like HNhx, respectively, the JXA1/mAb-PN9cx3 and HNhx/mAb-PN9cx3 groups were treated with mAb-PN9cx3 and challenged with HP-PRRSV-JXA1 and NADC30-like HNhx, respectively, and the JXA1/mAb-2G8 and HNhx/mAb-2G8 groups were administered the isotype mAb (2G8) and then challenged with HP-PRRSV-JXA1 and NADC30-like HNhx, respectively. For each group, representative images were captured immediately after piglets were autopsied at 21 dpi. B The gross pathological changes found in the animals of each group were quantified using a scoring (100-point) system. The significant differences between the mAb-PN9cx3-treated groups (JXA1/mAb-PN9cx3 and HNhx/mAb-PN9cx3) or the antibody-isotype control groups (JXA1/mAb -2G8 and HNhx/mAb-2G8) and the PRRSV-challenged groups (JXA1 and HNhx) are marked by asterisks: * (p < 0.05) and ** (p < 0.01).