Abstract: Objective To study the efficiency of protective immunity afforded by the constructed bivalent DNA vaccines of Schistosoma japonicum. Methods The plasmids pVIVO2-mcs-SjFABP-Sj23 and pVIVO2-mcs-Sj23-SjFABP， co-expressed bivalent DNA vaccines， were constructed and identified. The presence of bivalent DNA vaccine in the mouse muscle cells was also tested by indirect immunofluorescent antibody tests （IFAT）. 70 BALB/c mice were randomly divided into seven groups to be injected with normal saline, pVIVO2-mcs, pVIVO2-mcs-Sj23, pVIVO2-mcs-SjFABP, pVIVO2?-mcs-Sj23-SjFABP, pVIVO2-mcs-SjFABP-Sj23 plasmid DNA, and a mixture of pVIVO2-mcs-Sj23-SjFABP plasmid DNA and amylose adjuvant, respectively. At day 45 after challenge the mice were sacrificed. The number of adult worms and hepatic eggs were counted. Result Successful construction of co-expressed bivalent DNA vaccines were identified by restriction analysis and sequencing. It was confirmed by IFAT that the bivalent DNA vaccine was expressed in the plasma and on the surface of muscle cells from mouse. The worm reduction rate was 41.20%-53.85% and the egg reduction rate was 47.02%-53.83% bivalent DNA groups. Furthermore， the worm and egg reduction rates in pVIVO2-mcs-Sj23-SjFABP plasmid DNA and amylose adjuvant group were 68.89% and 84.04% respectively， significantly higher than single antigenic DNA vaccine and bivalent DNA vaccine （P<0.05）. Conclusion The co-expressed bivalent DNA vaccines of Schistosoma japonicum can induce immune protection in mice. The protective immunity of amylose adjuvant group is higher than that of the univalent DNA and bivalent vaccines.

Key words: Schistosoma japonicum, Sj23, SjFABP, DNA vaccine, Adjuvant