Abstract: 　Objective To subclone and express the gene encoding Schistosoma japonicum ferritin(SjFer)and study its immune protection against challenge infection in mice vaccinated intranasally. Methods The SjFer gene was amplified by PCR, and subcloned into the N-terminal of intein 2 of the pTWIN1 vector. The positive recombinant was screened by PCR, restriction enzyme digestion and sequence analysis. The positive recombinant was transformed into E. coli ER2566. The soluble recombinant fusion protein (rSjFer-intein 2) was expressed in E. coli by induction of low IPTG concentration under low temperature, and analyzed by SDS-PAGE and Western blotting. Mice were immunized intranasally with rSjFer, using chitosan as adjuvant. Two weeks after the third vaccination, challenge infection with S. japonicum cercariae was carried out. Worms and eggs collected from the livers of mice were counted at 42 days after the challenge. Levels of specific antibodies were detected by ELISA before infection. Results SjFer was successfully subcloned into pTWIN1 vector and expressed in E. coli. In mice vaccinated intranasally with rSjFer and adjuvant chitosan, the worm reduction rate was 35.51% and the reduction rate of eggs per gram liver tissue (LEPG) was52.17%. As compared with the control groups, levels of IgG, IgA in sera and SIgA in saliva increased significantly. Conclusion The expressed rSjFer can induce partial protective immunity against S. japonicum infection in mice when they were vaccinated intranasally, with chitosan as adjuvant.

Key words: Schistosoma japonicum, Ferritin, Chitosan, Mucosal immunization, Mouse