Development of a combined GMMA and glycoconjugate iNTS-TCV trivalent vaccine against invasive salmonellosis

Non-typhoidal Salmonella (NTS) is a leading cause of bloodstream infections associated with substantial mortality mostly in sub-Saharan Africa (sSA) in children under 5 years. Salmonella enterica serovars Typhimurium and Enteritidis account for more than 90% of invasive NTS (iNTS) infections. Typhoid fever is caused by S. enterica serovar Typhi and is relatively common in South and Southeast Asia and sSA, especially among children. While there are licensed vaccines to prevent S. Typhi infections, the only current intervention for iNTS disease is treatment with antibiotics. This work presents the preclinical development of a trivalent vaccine, iNTS-TCV, to prevent both iNTS disease and typhoid fever. This vaccine combines the Generalized Modules for Membrane Antigens (GMMA) technology for the iNTS components with the WHO-pre-qualified Vi-CRM₁₉₇ Typhoid Conjugate Vaccine (TCV). Immunization of mice with the iNTS-TCV candidate vaccine elicited higher anti-Vi IgG responses, characterized by a distinct IgG subclass profile, and greater serum bactericidal activity compared to responses induced by Vi-CRM₁₉₇ alone. In vitro immunoprofiling of human peripheral blood mononuclear cells revealed that the GMMA components drive a robust pro-inflammatory cytokine response, suggesting a potential mechanistic basis for the observed adjuvant effect on Vi-CRM₁₉₇ immunogenicity. The iNTS-TCV vaccine was well-tolerated in preclinical toxicology studies. These findings demonstrate the feasibility and potential benefits of combining GMMA and glycoconjugate vaccine technologies, offering a promising strategy for the prevention of both iNTS disease and typhoid fever. This trivalent vaccine approach may provide a sustainable and effective solution for addressing the significant burden of invasive salmonellosis in sSA.