Abstract: Objective To develop multivalent DNA vaccine PV-IL12-Sj23 which co-expresses Sj23 and cytokine IL-12, and investigate its protective efficacy in BALB/c mice against challenge infection. Methods On the basis of the reconstructed plasmid PV-IL12-Sj23 and plasmid PV-IL12, blank plasmid PV and plasmid PV-Sj23 only expressing Sj23 were constructed. Fifty BALB/c male mice were divided into five groups, which were immunized intramuscularly with multivalent DNA vaccine PV-IL12-Sj23, plasmid PV-Sj23 expressing Sj23, plasmid PV-IL12 expressing cytokine IL-12, blank plasmid PV and saline, respectively. Each mouse was immunized with 100 μg DNA only once. All the mice were challenged with 40 cercariae at week 4, killed and perfused for collection of worms at week10. The number of recovered worms and eggs in the liver were counted. Results Blank plasmid PV and plasmid PV-Sj23 expressing Sj23 were successfully constructed. The worm reduction rate in PV-IL12-Sj23 group and PV-Sj23 group was 45.5% and 27.2% (P<0.05) respectively. The number of eggs in liver tissue was reduced by 58.4% and 33.9% respectively. Conclusion Multivalent DNA vaccine PV-IL12-Sj23 can induce protective immunity against Schistosoma japonicum in BALB/c mice significantly, with a better protective efficacy than the monovalent DNA vaccine PV-Sj23.

Key words: Schistosoma japonicum, Membrane antigen, IL-12, Multivalent DNA vaccineImmunoprotection