Metronidazole/BSA is an antigen-adjuvant conjugate composed of metronidazole and bovine serum albumin (BSA). This conjugate, in combination with a protein adjuvant, is able to enhance antibody production against a specific antigen in vaccine models. The conjugate does not interfere with protein folding or disrupt major epitopes and helps enhance cross-presentation and the generation of antigen-specific T cells.