| To develop an effective vaccine, the screening, cloning, expression of the parasite genes and the immunoprotection testing have been done in this study. Method 1 The cDNA library of Schistosomajaponicum(Sj) adult worm was screened by sera of rabbits vaccinated with SjHmAg and the positive clones with inserts were confirmed by PCR. The sequence of three selected positive clones were finished and the data were analyzed by using the BLAST of NCBI online and the Expert Protein Analysis System. 2 The cDNA of SjCAI gene were subcloned into expression vector pGEX-5X-3. The recombinants of pGEX-SjCAI together with pGEX-Sj31b and pGEX-Sj31c (finished in our lab) were transformed to E.coli strain ER2566 and induced by IPTG, respectively. The mice were vaccinated with expressed proteins and the immunoprotective effect was tested, respectively. Result 1 Ten positive clones were obtained after three rounds of immunoscreening. The sequence of three selected positive clones had shown that partial sequence of one clone had significant homology with Sj tropomyosin(TM) and the others were novel genes named as SjHml and SjHm2, respectively. 2 Fusion proteins of SjGST-CAI, SjGST-31b and SjGST-31c were highly expressed in E. coli. Compared with the control group, the worm reduction rate in vaccination group of rSjGST-OAI, rSjGST-31bor rSjGST-31c was 29.87%, 22.71% or 13.6%; The liver egg reduction rate was 63.71%, 54.21% or 45.01%. Conclusion 1 The protein encoded by SjHml or SjHm2 is the possible candidate for vaccine of Sj and the exact function of the proteins await to be further investigated. 2 Both rSjGST-31b and rSjGST-31c can induce immunoprotective effect against Sj in mice, but rSjGST-31b is more effective than rSjGST-31c. 3 SjCAI gene can be highly expressed inE .coli after subcloned into pGEX-5X-3 vector . It is likely that rSjGST-CAI can induce significant effect of anti-embryonation and anti-infection immunity and it may be a potential new vaccine candidate against Sj infection.
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