Immunostimulant-integrated acrylate nanocomposite adjuvants potentiate foot-and-mouth disease vaccine efficacy.

Foot-and-mouth disease (FMD) is a viral infectious disease of artiodactyls that threatens the global livestock economy and public health security. Vaccination is employed to prevent the occurrence of infectious diseases, and adjuvants play a key role in vaccine preparation. Commercially available FMD vaccines mainly use oil-emulsion adjuvants that induce a humoral immune response in the body. Based on the acrylate hydrogel adjuvant (AHN) with sustained-release properties, this study introduced CpG, Poly I:C, and QS-21 immunostimulants to create an prepare immunostimulant-integrated acrylate nanocomposite adjuvant (AHN@X) combining excellent antigen delivery capability and immune response direction regulation for use in FMD vaccines. AHN@X has a particle size of less than 100 nm, and it exhibits good storage stability at 4 °C. The FMD vaccines prepared with AHN@X nanocomposite adjuvant were immunized by intramuscular injection in BALB/c mice. The results showed that it could efficiently induce specific IgG, IgG1 and IgG2a antibody titers and activate B cells and T cells. Moreover, AHN@C stimulated splenocytes to secrete cytokines IFN-γ and IL-4 at the highest concentrations, 58.34 pg/mL and 32.24 pg/mL respectively. Additionally, the AHN@C nanocomposite adjuvant promoted the strongest endocytosis of antigens by macrophages, and it efficiently induced humoral immune responses and cellular immune responses. Overall, the clinical protective efficacy of AHN@C against FMDV is worth subsequent validation in target livestock animals.