Toosendanin/OVA is an antigen-adjuvant conjugate of Toosendanin and ovalbumin (OVA). This conjugation enhances the production of antigen-specific antibodies in vaccine models by linking the antigen to a protein adjuvant. The conjugate does not alter protein folding or disrupt major epitopes, and it improves cross-presentation and the generation of antigen-specific T cells.