TbpBY167A-Based Vaccine Can Protect Pigs against Glasser's Disease Triggered by Glaesserella parasuis SV7 Expressing TbpB Cluster I

Glaesserella parasuis is the etiological agent of Glasser's disease (GD), one of the most important diseases afflicting pigs in the nursery phase. We analyzed the genetic and immunological properties of the TbpB protein naturally expressed by 27 different clinical isolates of G. parasuis that were typed as serovar 7 and isolated from pigs suffering from GD. All the strains were classified as virulent by LS-PCR. The phylogenetic analyses demonstrated high similarity within the amino acid sequence of TbpB from 24 clinical strains all belonging to cluster III of TbpB, as does the protective antigen TbpB(Y167A). Three G. parasuis isolates expressed cluster I TbpBs, indicating antigenic diversity within the SV7 group of G. parasuis. The antigenic analysis demonstrated the presence of common epitopes on all variants of the TbpB protein, which could be recognized by an in vitro analysis using pig IgG induced by a TbpB(Y167A)-based vaccine. The proof of concept of the complete cross-protection between clusters I and III was performed in SPF pigs immunized with the TbpB(Y167A)-based vaccine (cluster III) and challenged with G. parasuis SV7, strains LM 360.18 (cluster I). Additionally, pigs immunized with a whole-cell inactivated vaccine based on G. parasuis SV5 (Nagasaki strain) did not survive the challenge performed with SV7 (strain 360.18), demonstrating the absence of cross-protection between these two serovars. Based on these results, we propose that a properly formulated TbpB(Y167A)-based vaccine may elicit a protective antibody response against all strains of G. parasuis SV7, despite TbpB antigenic diversity, and this might be extrapolated to other serovars. This result highlights the promising use of the TbpB(Y167A) antigen in a future commercial vaccine for GD prevention.

Automated summary

We analyzed the genetic and immunological properties of Glaesserella parasuis strains isolated from pigs suffering from Glasser's disease. The study revealed antigenic diversity within the serovar 7 group, but common epitopes were identified on all variants of the TbpB protein. Immunization with a TbpB(Y167A)-based vaccine provided complete cross-protection between clusters I and III. These findings suggest the promising use of TbpB(Y167A) antigen in a future commercial vaccine for preventing Glasser's disease.