Rational Development of a Novel Emulgel Adjuvant for Single‐Shot Effective Vaccination: A Multivariate Analysis Approach

Abstract

AbstractNanoemulsions, like MF59, are potent vaccine adjuvants due to their immunogenicity, scalability, stability, and generation of broad cross‐clade neutralizing immune responses, facilitating their feasibility for pandemic preparedness. However, they are unsuitable for single‐shot applications due to limited immunogenicity with subunit antigens, and need to be explored for key immunogenic formulation variables like surfactant type, antigen anchoring, oil‐globule solidification, hydrogel polymer trapping, or globule size. Here, a multivariate analysis approach is used for the first time in adjuvant development, selecting 14 formulations from over 150, each with a unique formulation variable, to evaluate their immunological properties on C57BL/6 mice. Results show that nanoemulsions with hydrogel trapping, smaller globule size, or mannide monooleate cosurfactant significantly enhance immunogenicity, each by 5‐to‐10 folds over MF59. For the first time, these formulation variables are combined into an “optimized emulgel” that is predicted to maximize immunogenicity after a single shot, model fit gave (R2 = 0.97). The optimized emulgel triggers long‐lasting immune responses matching both the model's prediction and those triggered by the gold‐standard Freund's adjuvant against various antigens, while maintaining excellent safety. The findings highlight the potential of emulgels as a novel adjuvant class and underscore the utility of multivariate analysis in adjuvant design.