Nanobody-based combination vaccine using licensed protein nanoparticles protects animals against respiratory and viral infections.

Combination vaccines promise to simplify immunization schedules and improve coverage, but remain technically challenging owing to antigen compatibility, immunogenic balance and formulation complexity. Here we report a modular strategy that uses a single-component nanobody binder to noncovalently attach diverse antigens to intact particles from the licensed hepatitis E vaccine. To identify a suitable binder, an alpaca was immunized with the vaccine, and nanobodies were screened via phage display. One nanobody, P1-5B, selectively bound recessed, non-immunodominant sites on the particle surface and enabled stable antigen display without disrupting native immunogenicity. Using this binder, we generated three vaccine formulations displaying five to eleven antigens, including variants from SARS-2 coronavirus, influenza virus and respiratory syncytial virus. These multivalent particles exhibited high-affinity assembly, preserved solubility and induced neutralizing titres up to three log units higher than soluble antigens. In mice, hamsters and non-human primates, the candidate vaccines conferred robust protection and showed a favourable safety profile. This approach introduces a scalable, plug-and-display system for rapid development of customizable combination vaccines.