Characterization of multivalent vaccines against antimicrobial resistant pathogens

In recent years, the threat of antibiotic-resistant bacteria has become increasingly concerning. Vaccines are crucial tools in the fight against antimicrobial resistance (AMR), and multivalent polysaccharide-based vaccines are promising candidates for addressing this issue. However, developing these vaccines requires additional efforts, e.g. in terms of immunological evaluation including eventual immuno-interference, development of analytical methods for determining the characteristics of single antigens and the stability of the final multivalent combination. Generalized Modules for Membrane Antigens (GMMA) and glycoconjugation were compared for the development of an O-antigen-based tetravalent vaccine against Shigella, leading bacterial cause of diarrheal disease in low- and middle-income countries. GMMA offers good immunogenicity, functionality, and simplified manufacturing, making it a viable strategy for vaccine development. Originally targeting Shigella strains S. sonnei and S. flexneri 1b, 2a, and 3a, the vaccine's multivalency was expanded to hexavalency by adding glycoconjugates against Salmonella Typhi and Paratyphi A. This combination could address a significant unmet need and substantially contribute to AMR reduction. The technical feasibility of combining these six antigens was demonstrated, with no negative impact on the humoral immune response elicited by each of them in different animal models. The S. flexneri O-antigens have identical sugar compositions, posing challenges for individual quantification. To address this, a liquid chromatography-mass spectrometry method was developed to differentiate monomers based on their linkages in the O-antigen chain. Assessing vaccine stability is critical for safe and effective patient administration. Accelerated stability studies on the tetravalent Shigella GMMA vaccine have been conducted, and predictive models established to foresee vaccine behavior during storage and expedite vaccine development. Overall, this work advances multivalent saccharide-based vaccine development, contributing to AMR reduction and public health efforts.