A Unique Combination of Mn²⁺ and Aluminum Adjuvant Acted the Synergistic Effect

Introduction. The development of combinatorial adjuvants is a promising strategy to boost vaccination efficiency. Accumulating evidence indicates that manganese exerts strong immunocompetence and will become an enormous potential adjuvant. Here, we described a novel combination of Mn2+ plus aluminum hydroxide (AH) adjuvant that significantly exhibited the synergistic immune effect. Methodology. Initially, IsdB3 proteins as the immune-dominant fragment of IsdB proteins derived from Staphylococcus aureus (S. aureus) were prepared. IsdB3 proteins were identified by western blotting. Furthermore, we immunized C57/B6 mice with IsdB3 proteins plus Mn2+ and AH adjuvant. After the second immunization, the proliferation of lymphocytes was measured by the cell counting kit-8 (CCK-8) and the level of IFN-gamma, IL-4, IL-10, and IL-17 cytokine from spleen lymphocytes in mice and generation of the antibodies against IsdB3 in serum was detected with ELISA, and the protective immune response was assessed through S. aureus challenge. Results. IsdB3 proteins plus Mn2+ and AH obviously stimulated the proliferation of spleen lymphocytes and increased the secretion of IFN-gamma, IL-4, IL-10, and IL-17 cytokine in mice, markedly enhanced the generation of the antibodies against IsdB3 in serum, observably decreased bacterial load in organs, and greatly improved the survival rate of mice. Conclusion. These data showed that the combination of Mn2+ and AH significantly acted a synergistic effect, reinforced the immunogenicity of IsdB3, and offered a new strategy to increase vaccine efficiency.