Porcine GM-CSF and APS as a novel complex immunostimulant improves the immune effect of pseudorabies inactivated vaccine

Currently, pseudorabies (PR) is mainly controlled with attenuated and inactivated vaccines. In the case of inactivated vaccines, immunostimulants play a crucial role in triggering the host immune response. In this study, granulocyte-macrophage colony-stimulating factor (GM-CSF) and astragalus polysaccharide (APS) were investigated as a novel complex immunostimulant in inactivated PR vaccine. The findings indicated that neither porcine GM-CSF (pGM-CSF) nor APS exhibited any cytotoxic effect on cells. In addition, the PR vaccine+pGM-CSF+APS group exhibited higher levels of PRV-specific gB and neutralizing antibodies. Moreover, the group treated with pGM-CSF+APS immunostimulants demonstrated a notable increase in the production of IL-4, IL-10, IL-2, IFN-γ. After PRV challenge, the PR vaccine with pGM-CSF and APS alleviated clinical symptoms and reduced mortality. Additionally, the complex immunostimulant group showed a lower viral DNA copy number in various tissues compared to the PR vaccine alone group, as well as the groups treated with PR vaccine+pGM-CSF and PR vaccine+APS. Moreover, mice challenged with PRV in the PR Vaccine+pGM-CSF+APS group reduced substantial tissue lesions than other groups. These results demonstrate the potential of pGM-CSF and APS when used together as complex immunostimulant to enhance both humoral and cellular immune responses to inactivated vaccines, providing novel perspectives for the further development of immunostimulants.