Evaluation of Cholera Toxin B Subunit as a Novel Carrier Protein for Polysaccharide Conjugate Vaccines

<b>Background:</b> The immunogenicity of polysaccharide conjugate vaccines is critically influenced by the choice of carrier protein, which promotes a T-cell-dependent immune response mechanism leading to strong antibody production. In this study, the cholera toxin B subunit (CTB), a non-toxic pentameric protein, was evaluated as a novel carrier protein for pneumococcal polysaccharide antigens. <b>Methods</b>: Recombinant CTB was produced in <i>Escherichia coli</i> and purified using scalable chromatographic methods. Pneumococcal polysaccharides from serotypes 7F, 22F, and 33F were chemically activated with CDAP and conjugated to CTB. <b>Results:</b> The resulting glycoconjugates were characterized by SEC-MALS, confirming successful conjugation, high molecular weights, consistent polysaccharide-to-protein ratios, and acceptable endotoxin levels. Immunogenicity was assessed in rabbits following immunization with alum-adjuvanted formulations. <b>Conclusions</b>: Robust IgG responses were elicited by all CTB-based conjugates, with antibody levels found to be comparable to those induced by CRM197 conjugates, demonstrating the potential of CTB as a promising alternative for the next generation of conjugate vaccines.