Programmable trivalent nanocage vaccine confers durable cross-species protection against Bordetella bronchiseptica infection

Bordetella bronchiseptica (B. bronchiseptica), a respiratory pathogen endemic in companion animals, poses an escalating zoonotic threat to humans due to intensified human-pet contact, particularly among immunocompromised individuals. Here, we report a programmable trivalent nanocage vaccine, mi3-F1P2Fim2, featuring immunodominant regions of FHA, Prn, and Fim2 covalently fused into a single-chain construct and displayed on a self-assembling mi3 nanocage via the SpyTag003/SpyCatcher003 system, enabling high-density and multivalent antigen presentation. Compared with its soluble monomeric counterpart, mi3-F1P2Fim2 induced significantly enhanced humoral and cellular immune responses, characterized by a 1.98-fold elevation in antigen-specific IgG titers, improved IgG1/IgG2a subclass balance, and heightened dendritic cell activation. The vaccine facilitated efficient uptake by antigen-presenting cells and induced robust germinal center reactions. Notably, mi3-F1P2Fim2 conferred complete protection against B. bronchiseptica challenge in both murine and canine models, achieving > 1000-fold reduction in pulmonary bacterial burden with concomitant alleviation of lung pathology. These data demonstrate that mi3-F1P2Fim2 confers potent, cross-species protective immunity against B. bronchiseptica, establishing it as a promising vaccine candidate for preventing zoonotic respiratory infections. By targeting this clinically significant but understudied pathogen, our findings advance strategies to disrupt B. bronchiseptica transmission and enable targeted immunization aligned with One Health objectives.