The BP26-OMP16Es Nanoparticle Vaccine Elicits Protective Immunity against Brucella

Abstract Brucellosis, a major global zoonosis causing over 2.1 million human infections annually, poses a significant threat to public health and livestock economies. Conventional vaccines face substantial limitations, including residual virulence and diagnostic interference in live attenuated vaccines, and poor immunogenicity in subunit vaccines. To address these issues, we developed BP26-OMP16Es, a self-assembling nanoparticle vaccine constructed by fusing immunodominant B- and T-cell epitopes from OMP16 to the self-assembling antigen BP26 via flexible linkers, yielding single-copy (1×) and double-copy (2×) epitope tandem nanoparticles. These particles formed homogeneous, barrel-shaped structures (14–23 nm) with strong immunoreactivity against Brucella-specific antibodies. In murine models, the vaccine elicited potent humoral and cellular immune responses, characterized by high antibody titers, enhanced IFN-γ+ CD8+ T cell proliferation, a balanced Th1/Th2 profile, and the induction of immunological memory for durable protection. Immune sera also mediated effective clearance of infected macrophages via antibody-dependent cellular cytotoxicity (ADCC). Challenge experiments confirmed that the vaccine significantly reduced splenic Brucella burden and alleviated pathological damage, with the 2× construct offering superior protection. In summary, this study integrates self-assembling nanotechnology with a multiepitope strategy to create a safe and potent vaccine platform. The 2× design enhances epitope density, boosting immunogenicity and conferring solid protection against Brucella infection. This approach provides valuable insights for developing vaccines against brucellosis and other intracellular pathogens.