Astragalus Polysaccharide Nanoemulsion: A Promising Adjuvant for Foot-And-Mouth Disease Virus-Like Particle Vaccines

Vaccine immunization is the most cost-effective way for preventing infectious diseases, and the development of safe and effective adjuvants is crucial for ensuring vaccine efficacy. Due to the advantages of high safety profile, excellent stability, and significant immune-enhancing properties, nanoemulsions have become widely used adjuvants in animal vaccines. In this study, a novel astragalus polysaccharide nanoemulsion (APSN) was developed using pseudo-ternary phase diagram method combined with phase inversion technique. The resulting nanoemulsion exhibited a hydrated diameter of approximately 78.82 nm, with favorable stability and biocompatibility. A vaccine based on FMDV virus-like particles (VLPs) was formulated using APSN as an adjuvant and was used to immunize mice and pigs. Mouse immunization results demonstrated that APSN significantly enhanced the levels of specific antibodies, IgG1, IgG2a, IFN-γ, and IL-4 induced by FMDV VLPs. Comparing with ISA-206, immunization in pigs showed that APSN paired with FMDV VLPs induced higher levels of specific antibodies, neutralizing antibodies, IL-1β, IL-4, and IFN-γ. The above results indicate that APSN is a new type of nanoemulsion adjuvant with strong potential to enhance vaccine immunogenicity, contributing valuable insights to the development of nanoadjuvant-based vaccine formulations.