Versatile functionalization of ferritin nanoparticles by intein-mediated trans-splicing for antigen/adjuvant co-delivery.

Self-assembling protein nanoparticles are extensively and increasingly engineered to integrate adjuvants with antigens to elicit potent and long-term immunity due to uniform architecture, inherent biocompatibility, and excellent plasticity. However, functionalization of nanoparticles by surface tailoring has two common problems: (1) disassembly caused by loaded cargoes; and (2) an adjuvant that is inconvenient to co-deliver with an antigen by genetic fusion. Here, we report an intein-mediated trans-splicing approach that overcomes the detrimental effects of loaded proteins on ferritin nanoparticle stability and allows concurrent display of antigen and adjuvant in a facile, efficient, and site-specific manner. An immunization study with an epitope-based model antigen reveals that antigen and adjuvant co-delivery nanoparticles induce a more potent protective immunity than other formulations do. Our results demonstrate that protein engineering represents an intriguing approach for antigen/adjuvant co-delivery to potentiate antigen-associated immune responses.