Streptococcus equi ssp. zooepidemicus C5a peptidase, a putative invasin, induces protective immune response in mice

Streptococcus equi ssp. zooepidemicus (Streptococcus zooepidemicus, SEZ) is responsible for septicemia, meningitis, arthritis and several other serious diseases in various species with adhesive and invasive properties. The absence of suitable vaccine confounds the control of SEZ infection. The highly conserved C5a peptidase was served as an invasin to host epithelial cells and involved in the pathogenicity in other streptococcus species. In the present study, the purified recombinant SEZ C5a peptidase (rSCPZ) could adhere to Hep-2 cells and interfere with the invasion of SEZ into Hep-2 cells confirmed by adherence and invasion assay. Immunization of BALB/c mice with rSCPZ could elicit a significant humoral antibody response and could confer significant protection against challenge with a lethal dose of SEZ. In addition, the hyperimmune sera against rSCPZ could efficiently inhibit bacterial growth in a whole blood assay and confer significant protection against SEZ infection in the experiment of passive immunization. The present study suggests that SCPZ could be useful for development of subunit vaccine against SEZ.