In this project, we have used the rapid developments in protein design and quantitative and structural mass spectrometry to establish a framework for antibody-guided design of protein-based nanoparticle immunogens against GAS. We first developed a mass spectrometry based systems antigen-omics and systems serology workflow to select antigens in a data-driven manner. With these antigens as a starting point, monoclonal antibodies directed against key antigens were developed to define protective epitopes. These epitopes are in the final step redesigned and used to produce immunogens that display one or several epitopes in one immunogen. The immunogens assemble from two protein components i) a fusion component that carry the epitope and ii) the assembly component that when mixed, form ~3MDa icosahedral protein nanoparticles.

We have used the workflow to produce a proof-of-concept monovalent self-assembling protein-based nanoparticle immunogen against Streptolysin O (SLO). For this immunogen, integrated structural mass spectrometry techniques and deep learning approaches were combined to re-engineer a protective epitope (D3m) present in domain 3 of SLO. D3m was displayed on the surface of a self-assembling icosahedral nanoparticle (D3m-NP) to enhance epitope presentation and immunogenicity. Immunising mice with D3m-NP, induced a robust and epitope-focused antibody response leading to improved protection against a lethal GAS challenge compared to immunisation with a detoxified full-length SLO vaccine construct. The approach can be extended to other antigens to explore the possibility of developing multivalent protein-based nanoparticle immunogens against GAS.