Studies On The Clone, Expression And Protective Immunity Of The Calreticulin Of Schistosoma Japonicum

Objective: To look for a new vaccine candidate of S. japonicum (Chinese mainland strain) by the way of signal transduction intervention, the protein SjCRT coding gene from cDNA of S.japonicum adult worms was amplified and cloned into prokaryotic expression vector to express the recombinant protein (rSjCRT). To prepare the rSjCRT protein vaccines to estimate the immuno-protection in mice challenged with cercaria. Methods:The total RNA of S. japonicum was extracted to prepare for cDNA by RT-PCR, from which the SjCRT coding gene was amplified. Following ligation of the target SjCRT DNA fragments to expression vector pET28a, the fusion protein SjCRT with6-His tag was expressed in E.coli BL21. The protein of the14-3-3were prepared and purified, then BALB/c mice were immunized followed by challenging infection and the immuno-protection was evaluated. We also observed the OD450value of the specificity antibody by indirect ELISA. Results:The size of PCR-created product was approximately1191bp. And the insert of pET28a-SjCRT digested with BamH I and Xho I was the same in length as the PCR product. With the positive clone induced by IPTG, the fusion protein was expressed in E.coli BL21. The molecular weight of the protein is about45kDa. the expression band can be recognized by the sera of rabbit infected with cercaria. The results of the immuno-protective experiments showed that the worm reduction was23.98%,28.78%,35.06%in group1,2and3; the number of eggs in liver tissue was reduced by35.52%,40.24%,43.46%, respectively. Indirect ELISA showed that the rSjCRT has produced the specificity antibody in mouse. Conclusions:The calreticulin (CRT) gene was successfully amplified, cloned and expressed. The molecular vaccine of SjCRT could partially induce resistance to the infection with S. japonicum in BALB/c mice.