Development and protection evaluation of a nanoparticle vaccine against transferrin-binding protein TbpBY167A of Glaesserella parasuis.

In this study, a novel nanoparticle vaccine that can efficiently display the protective antigen TbpBY167A of Glaesserella parasuis was constructed using the self-assembly property of the capsid (Cap) protein of porcine circovirus type 3 (PCV3). Traditional subunit vaccines against Glässer's disease often suffer from insufficient immunogenicity and suboptimal protective efficacy. The vaccine developed in the present study efficiently elicits both humoral and cellular immune responses via multivalent antigen display, leading to substantially enhanced overall adaptive immunity. This work therefore provides promising vaccine candidates with high safety and improved protective efficacy for the prevention and control of Glässer's disease.Monoclonal antibodies (MAbs) against TbpBY167A were generated using recombinant TbpBY167A protein expressed in E. coli and their epitope characteristics were identified and which can specifically react with TbpBY167A displayed on the surface of VLP (Virus-Like Particle). A recombinant baculovirus expressing the Cap protein of PCV3 fused with TbpBY167A at the N terminus was constructed. Guinea pigs were immunized with the nanoparticle vaccine and a conventional subunit vaccine (MBP-TbpBY167A), humoral immune responses, cytokine profiles, pathological changes, and protection rates after challenge were compared. One stable hybridoma cell line, designated 2D3, secreting MAbs against TbpBY167A was obtained, and its recognized epitope was mapped to a linear region spanning amino acids 269-275. Transmission electron microscopy confirmed that the Cap-TbpBY167A fusion protein self-assembled into homogeneous nanoparticles approximately 20 nm in diameter. Animal experiments showed that both the nanoparticle vaccine and the subunit vaccine elicited robust specific antibody responses and provided a 60% protection rate against lethal challenge. Notably, the nanoparticle vaccine group exhibited significantly milder histopathological lesions in the lungs and spleen compared with the subunit vaccine and challenge control groups. The Cap-TbpBY167A nanoparticle vaccine confers protection against lethal G. parasuis challenge and demonstrates less lesions of target organ pathology compared with the conventional subunit vaccine. The success of this study provides a novel antigen delivery strategy for the development of broad-spectrum vaccines against G. parasuis.