Abstract: 　Objective To develop 23 kDa membrane protein DNA vaccine of Schistosoma japonicum Chinese strain and test its protective efficacy in infected C57BL/6 mice. Methods The full length cDNA encoding SjC23 amplified from pUC19 SjC23 subcloned into pcDNA3.1. 48 female mice were divided into three groups: A, B and C. Group A (control group) was each immunized im with 100 μg of pcDNA3.1; group B (SjC23 group) was each immunized im with 100 μg of pcDNA3.1 SjC23; group C (SjC23+IL 12) was each immunized im with a mixture of 100 μg of pcDNA3.1 SjC23, 100 μg of pcDNA3.1 p35 and 100 μg of pcDNA p40, followed by two boosts of the same DNA once every two weeks. All the mice were challenged with 45 cercariae at week 8, killed and perfused for worms at week 14. The expression of SjC23 and p35, p40 in muscle tissue was determined by immuno histochemical method. By the culture of spleen cells, the production of IL 2,IL 4,IL 10 and IFN γ after the stimulation of rSjC23 HD was determined two weeks before and after challenge. Anti SjC23 antibodies were tested by Western blotting. Results SjC23 and p35, p40 were all expressed on the membrane and in the plasma of muscle cells of the infected mice. Significant increase of IL 2 and IFN γ in SjC23 and SjC23+IL 12 groups was observed before and after challenge. Western blotting showed that after the third immunization (before challenge) 8 out of 10 sera from SjC23 group and 9 out of 10 sera from SjC23+IL 12 group were positive. The worm reduction rate in SjC23 group and SjC23 +IL 12 group was 26.9% and 35.4%, respectively; the number of eggs in liver tissue was reduced by 22.2% and 28.4%, respectively. Conclusion pcDNA3.1 SjC23 DNA vaccine could induce partial protection against Schistosoma japonicum in C57BL/6 mice.

Key words: Schistosoma japonicum, 23 kDa membrane protein, DNA vaccine, protective immunity