Orientation of Antigen Display on Self-Assembling Protein Nanoparticles Influences Immunogenicity.

Cosette G Schneider,Carole A Long,Evelina Angov,Gary R Matyas,Elke Bergmann-Leitner,Justin A Taylor,Christopher Karch,Zoltan Beck,Kazutoyo Miura,Michael Q Sibilo,Peter Burkhard,Katherine L Mallory,Christopher Mann

doi:10.3390/vaccines9020103

Abstract

Self-assembling protein nanoparticles (SAPN) serve as a repetitive antigen delivery platform with high-density epitope display; however, antigen characteristics such as size and epitope presentation can influence the immunogenicity of the assembled particle and are aspects to consider for a rationally designed effective vaccine. Here, we characterize the folding and immunogenicity of heterogeneous antigen display by integrating (a) dual-stage antigen SAPN presenting the P. falciparum (Pf) merozoite surface protein 1 subunit, PfMSP119, and Pf cell-traversal protein for ookinetes and sporozoites, PfCelTOS, in addition to (b) a homogenous antigen SAPN displaying two copies of PfCelTOS. Mice and rabbits were utilized to evaluate antigen-specific humoral and cellular induction as well as functional antibodies via growth inhibition of the blood-stage parasite. We demonstrate that antigen orientation and folding influence the elicited immune response, and when appropriately designed, SAPN can serve as an adaptable platform for an effective multi-antigen display.

Highlights

In 2019, the World Health Organization estimated 229 million cases of malaria and roughly 409,000 deaths worldwide, underscoring its continued prevalence as a global health threat [1]
The Self-assembling protein nanoparticles (SAPN) structures generated in this study aimed to explore the effect of orientation of antigen display on the immunogenicity of a multi-stage malaria vaccine candidate
SAPN displaying PfMSP119 and PfCelTOS were generated by two purification processes, one allowing for disulfide bridges to form first under non-denaturing, oxidative affinity chromatography followed by denaturing conditions on ion exchange and the second using denaturing/reductive conditions throughout the chromatography, which allowed for disulfide bridges to form during the final refolding steps

Summary

Introduction

In 2019, the World Health Organization estimated 229 million cases of malaria and roughly 409,000 deaths worldwide, underscoring its continued prevalence as a global health threat [1]. In high-transmission areas, children under the age of five are among the most vulnerable, accounting for 67% of global malaria deaths [1]. Malaria infection occurs when infected Anopheles mosquitoes introduce Plasmodium parasites into the host during a blood meal. Plasmodium falciparum (Pf) is the leading cause of malaria morbidity and mortality, and in 2017, 2.6 billion people inhabited areas at risk of P. falciparum transmission, prompting this parasite species to be the focus of extensive efforts for vaccine development [2]. The most advanced candidates, RTS,S and PfSPZ vaccines, while attaining high levels of protection against homologous strain parasites in controlled human malaria infections [6,7], achieved partial efficacy against natural infection [7,8,9,10,11,12,13,14]. The lack of effective vaccines and the severity of malaria infections necessitate the evaluation of novel vaccine technologies

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