Objective The objective of this study was to construct a recombinant Salmonella choleraesuis strain co-expressing GAPDH and OmP26, two immunogenic antigens derived from Glaesserella parasuis, evaluate its potential as a bivalent vaccine candidate, and provide a novel and efficacious solution for the prevention of both G. parasuis and S. choleraesuis infections in swine populations.

Method GAPDH and OmP26, which are widely present in various serotypes of G. parasuis, were selected as exogenous antigens. A recombinant strain of G. parasuis-S. choleraesuis, which was capable of expressing both the GAPDH and OmP26, was constructed by using S. choleraesuis C500Δasd deletion strain as vector. The biological characteristic and immune effect of the recombinant strain were then investigated.

Result Results of PCR and Sanger-sequencing showed that the recombinant strain C501 (pYA-GAPDH-OmP26) was successfully constructed, which was able to stably harbor GAPDH and OmP26 (sizes of 1 020 and 798 bp, respectively) . The target fragments were stably amplified from the strain in 100 consecutive passages, and the recombinant strain was consistent with the parent strain C501(pYA3493) in terms of growth curves and biochemical characteristics. The recombinant strain C501 (pYA-GAPDH-OmP26) showed 62.5% and 50.0% protection rates against S. choleraesuis C78-1 and G. parasuis type 5 strong strain SH0165, respectively, while C501 (pYA3493) showed 50.0% protection rate against S. choleraesuis C78-1 and no protection effect against G. parasuis type 5 strong strain SH0165.

Conclusion The recombinant S. choleraesuis C501 (pYA-GAPDH-OmP26) can stably carry heterologous genes. Compared with the parent strain, the recombinant strain has similar biological and good expression characteristics, can induce the organism’s combined immune response against G. parasuis and S. choleraesuis. The study lays the foundation for the development of the bivalent genetically engineered vaccine for G. parasuis and S. choleraesuis.