A Bivalent MAPS Vaccine Induces Protective Antibody Responses against Salmonella Typhi and Paratyphi A

Multiple antigen presenting system (MAPS): state of the art and potential applications

INTRODUCTION

Technological innovations have been instrumental in advancing vaccine design and protective benefit. Improvements in the safety, tolerability, and efficacy/effectiveness profiles have profoundly reduced vaccine-preventable global disease morbidity and mortality. Here we present an original vaccine platform, the Multiple Antigen Presenting System (MAPS), that relies on high-affinity interactions between a biotinylated polysaccharide (PS) and rhizavidin-fused pathogen-specific proteins. MAPS allows for flexible combinations of various PS and protein components.

AREAS COVERED

This narrative review summarizes the underlying principles of MAPS and describes its applications for vaccine design against bacterial and viral pathogens in non-clinical and clinical settings.

EXPERT OPINION

The utilization of high-affinity non-covalent biotin-rhizavidin interactions in MAPS allows for combining multiple PS and disease-specific protein antigens in a single vaccine. The modular design enables a simplified exchange of vaccine components. Published studies indicate that MAPS technology may support enhanced immunogenic breadth (covering more serotypes, inducing B- and T-cell responses) beyond that which may be elicited via PS- or protein-based conjugate vaccines. Importantly, a more detailed characterization of MAPS-based candidate vaccines is warranted, especially in clinical studies. It is anticipated that MAPS-based vaccines could be adapted and leveraged across numerous diseases of global public health importance.

Dual immunization with CdtB protein and flagellin epitope offers augmented protection against enteric fever in mice

AIMS

Present study has explored the protective response of dual immunization using two different antigenic entities (i.e. flagellin epitope and cytolethal distending toxin subunit B (CdtB) protein) against lethal challenge of typhoidal serovars in a murine model.

MAIN METHODS

In-vitro immunogenicity of flagellin epitope-BSA conjugate and CdtB protein was confirmed using Indirect ELISA of typhoid positive patients' sera. Further, both entities were administered intraperitoneally in mice individually or in combination, followed by lethal challenge of typhoidal Salmonellae. Various parameters were analysed such as bacterial burden, mice survival, histopathological analysis, cytokine analysis and immunophenotyping. Serum samples obtained from the immunized mice were used for passive immunization studies, wherein mice survival and mechanism of action of the generated antibodies was studied.

KEY FINDINGS

Active immunization studies using the combination of both entities demonstrated improved mice survival after lethal challenge with typhoidal Salmonellae, reduced bacterial burden in organs, expression of immunophenotypic markers in splenocytes and restored tissue histoarchitecture. When used in combination, the effective doses of both the candidates reduced which may be attributed to multiprong approach used by the immune system to recognize Salmonella. Passive immunization studies further determined the protective efficacy of generated antibodies by different mechanisms such as complement mediated bactericidal action, swarming inhibition and increased phagocytic uptake.

SIGNIFICANCE

Present study is the first phase of the proof-of-concept which may prove to be beneficial in developing an effective bi-functional vaccine candidate to render protection against both Vi-positive as well as Vi-negative Salmonella strains.

Induction of Broad Immunity against Invasive Salmonella Disease by a Quadrivalent Combination Salmonella MAPS Vaccine Targeting Salmonella Enterica Serovars Typhimurium, Enteritidis, Typhi, and Paratyphi A

Bloodstream infections in low- and middle-income countries (LMICs) are most frequently attributed to invasive Salmonella disease caused by four primary serovars of Salmonella enterica: Typhi, Paratyphi A, Typhimurium, and Enteritidis. We showed previously that a bivalent vaccine targeting S. Typhi and S. Paratyphi A using a Multiple Antigen-Presenting System (MAPS) induced functional antibodies against S. Typhi and S. Paratyphi. In the current study, we describe the preclinical development of a first candidate quadrivalent combination Salmonella vaccine with the potential to cover all four leading invasive Salmonella serotypes. We showed that the quadrivalent Salmonella MAPS vaccine, containing Vi from S. Typhi, O-specific Polysaccharide (OSP) from S. Paratyphi A, S. Enteritidis and S. Typhimurium, combined with the Salmonella-specific protein SseB, elicits robust and functional antibody responses to each of the components of the vaccine. Our data indicates that the application of MAPS technology to the development of vaccines targeting invasive forms of Salmonella is practical and merits additional consideration.

Evolution of Vaccines Formulation to Tackle the Challenge of Anti-Microbial Resistant Pathogens

The increasing diffusion of antimicrobial resistance (AMR) across more and more bacterial species emphasizes the urgency of identifying innovative treatment strategies to counter its diffusion. Pathogen infection prevention is among the most effective strategies to prevent the spread of both disease and AMR. Since their discovery, vaccines have been the strongest prophylactic weapon against infectious diseases, with a multitude of different antigen types and formulative strategies developed over more than a century to protect populations from different pathogens. In this review, we review the main characteristics of vaccine formulations in use and under development against AMR pathogens, focusing on the importance of administering multiple antigens where possible, and the challenges associated with their development and production. The most relevant antigen classes and adjuvant systems are described, highlighting their mechanisms of action and presenting examples of their use in clinical trials against AMR. We also present an overview of the analytical and formulative strategies for multivalent vaccines, in which we discuss the complexities associated with mixing multiple components in a single formulation. This review emphasizes the importance of combining existing knowledge with advanced technologies within a Quality by Design development framework to efficiently develop vaccines against AMR pathogens.