Synergistic effect of LTB and Mn²⁺ adjuvants on immunogenicity of multi-epitope peptides from Staphylococcus aureus

Here, a novel combined adjuvant of heat-labile enterotoxin B (LTB) as an intramolecular adjuvant plus Mn²⁺ was prepared to enhance the immunogenicity of multi-epitope (MEP) peptides derived from Staphylococcus aureus (S. aureus). Initially, the mep and ltb-mep fragments were amplified and inserted into pET-28a vectors, respectively, to generate the recombinant plasmids pET28a-mep and pET28a-ltb-mep. Then, the expression of MEP and LTB-MEP was verified by Western blot. Subsequently, the MEP and LTB-MEP proteins were subjected to bioinformatics analysis. Kunming mice were immunized with the LTB-MEP proteins plus Mn²⁺ adjuvants. After the second immunization, the mice immunized with LTB-MEP plus Mn²⁺ exhibited significantly enhanced splenic lymphocyte proliferation, increased secretion of IFN-β, IFN-γ, IL-2, IL-6, and IL-17 by splenic lymphocytes, and significantly enhanced the generation of antibodies against MEP in serum, and improved survival rate following S. aureus challenge. The data showed that the novel LTB-Mn²⁺ combined adjuvant exerted a synergistic effect, significantly enhanced the immunogenicity of MEP, and provided a new strategy for improving the efficacy of vaccines against S. aureus.