Identification of a surface protective antigen, MAP of Streptococcus equi subspecies zooepidemicus

Streptococcus equi subspecies zooepidemicus (SEZ) is a zoonotic pathogen with adhesive and invasive properties. Due to the shortcomings of antibiotics and traditional inactivated vaccine, identifying protective antigens against SEZ would be helpful to the development of novel vaccines. MAP has been identified as a membrane anchored protein with a typical LPXTG-like cell wall-anchored motif. In present study, the objective was to evaluate the effects of MAP as a subunit vaccine with mouse model. The Western blot analysis shown that the purified recombinant MAP presented good immunoreactive to convalescent porcine sera against SEZ. The protein could elicit a remarkable humoral antibody response and protect 80% of mice against lethal dose challenge of SEZ in mouse model. Moreover, the hyperimmune sera against MAP could efficiently kill the bacteria in whole blood killing assay and conferred significant protection against SEZ in passive immunization experiments. This study suggests with good reasons that MAP could be a novel and effective vaccine candidate for SEZ.