Abstract: 　AIM: To explore the protective immunity against cercariae challenge in mice immunized with Sj32DNA vaccine of Schistosoma japonicum. METHODS: Primers were designed and the full length and part cDNA encoding 32 kDa(Sj32) amplified from pSj32 by PCR were cloned into pBK CMV. Eukaryotic expression vector pBK Sj32 1 containing full length Sj32 cDNA and pBK Sj32 2 containing fragment of Sj32 cDNA were constructed. After selection and identification, two plasmids were transfected into NIH 3T3 cells. The expression of Sj32 in transfected cells was confirmed by IFA. After identification, the two plasmids were prepared and purified on batches. Each BALB/c mouse was vaccinated at weeks 0,3, and 5, by injection with 100 μg of purified Sj32DNA into quadriceps muscle. Mice immunized with constructs and the control mice were challenged four weeks after final DNA injection, and worms and the number of eggs in the liver tissue were counted at 8 weeks after challenge. RESULTS: Perfusion and egg counts showed significant differences in terms of worm reduction rate 38 6%-30 9% and egg reduction rate 55 7%-55 2% between the vaccinated and control mice. CONCLUSION: Sj32 DNA vaccine could result in protection against a subsequent challenge of S.japonicum in mice.

Key words: Schistosoma japonicum, asparaginyl endopeptidase, DNA vaccine, protective immunity