Protective immunity of native SpaA and recombinant SpaA-N against Erysipelothrix rhusiopathiae infection in mice

Abstract:

Abstract: [Objective] The purpose of this study was to evaluate the protective effects of surface protective antigen A (SpaA) and its N-teminal protective domain (rSpaA-N) against Erysipelothrix rhusiopathiae infection in mice. [Methods] The SpaA was purified by electroelution from NaOH-extracted antigen of Erysipelothrix rhusiopathiae strain C43311. The rSpaA-N was expressed in E. coli BL21 as a soluble protein by IPTG inducing，and purified with GST affinity chromatography. Mice of each group were subcutaneously immunized three times with 50μg or 100 μg of native SpaA, rSpaA-N or NaOH-extracted antigen with in complete or incomplete Freund adjuvant at 2-week intervals. Five mice of each group were challenged with 100 LD50 of Erysipelothrix rhusiopathiae virulent strain C43065 two weeks after the third immunization, and the specific antibody responses for SpaA was determined by indirect ELISA. [Results] Mice immunized with 50 μg or 100 μg of native SpaA，rSpaA-N，or NaOH-extracted antigen were protected completely against the challenge with strain C43065. There was no significant difference (P<0.05) between the antibody responses observed for native SpaA，rSpaA-N and NaOH-extracted antigen at any dosages. Western blot results indicated that the native SpaA and rSpaA-N were recognized specifically by an antiserum against the native SpaA of strain C43311. [Coclusion] These results demonstrated that the rSpaA-N is a protective antigen of Erysipelothrix rhusiopathiae serotype 2 strains, and might be a useful vaccine candidate against swine erysipelas.