Deletion of glpK in Salmonella Choleraesuis decreases virulence and confers immune protection in mice.

Salmonella Choleraesuis one of the zoonotic pathogens and seriously affecting public health security. Here, a glycerol kinase glpK mutant (ΔglpK) of Salmonella Choleraesuis was constructed, and its virulence was detected, we also evaluated the protective ability of the mutant ΔglpK as a live attenuated vaccine candidate in mice. Compared to the wild type strain, ΔglpK did not show significant difference in growth and biochemical properties, but had significantly reduced the ability of colonization in RAW 264.7 mouse macrophage cells and in mice. The proliferative activity and apoptosis of RAW 264.7 cells significantly increased and decreased, respectively following loss of glpK, the virulence of ΔglpK was also significantly reduced in mice. Then highly specific humoral and cellular immune responses were induced after intraperitoneal vaccination with ΔglpK (5 × 105 CFU/mouse), the growth performance was no significant difference between vaccinated and unvaccinated mice, and ΔglpK could persist more than 14 days post-immunization, finally 100% protection was provided by ΔglpK in mice after challenge. These results indicate that deletion of glpK decreases the virulence of Salmonella Choleraesuis and confers immune protection, the mutant ΔglpK could be used as a live attenuated vaccine candidate.