Identification of a novel protective antigen, 3-oxoacyl-[acyl-carrier-protein] synthase II of Streptococcus equi ssp. zooepidemicus which confers protective effects.

Streptococcus equi ssp. zooepidemicus (SEZ) is an important swine pathogen and responsible for a wide variety of infections in many animal species. FabF was a novel protein identified in the previous study. However, its protective efficacy remained to be evaluated. In this study, recombinant fabF of SEZ was expressed and showed a strong immunoreactivity with mini-pig convalescent sera. Study in mice revealed that the recombinant protein induced a marked antibody response and protected 80% of mice against SEZ infection. The hyperimmune sera against fabF could efficiently kill the bacteria in the phagocytosis test. In addition, it was also found that anti- fabF antibodies can significantly inhibit the formation of SEZ biofilm. These study suggest that fabF may represent immunogens of interest for vaccine development against SEZ infection.