Abstract: 【Abstract】 Objective To clone and express endothelial differentiation-elated factor（SjEDF）- gene of Schistosoma japonicum， analyze its immunogenicity and the stage-pecific expression at different developmental stages of S. japonicum. Methods Total RNA were extracted from eggs, cercariae, schistosomula and adult worms. The housekeeping gene SjActin was selected as the internal reference. According to the open reading frame for SjEDF- gene （GenBank accession number: AY336498）, a pair of primers were designed to amplify the SjEDF- gene which was subc-oned into pET-8a vector. The recombinant plasmid SjEDF-/pET-8a was transformed into E. coli BL21 and induced with IPTG for expression. The recombinant protein was purified with Ni-TA resin. The immune rabbit sera was prepared by immunizing New Zealand white rabbits with purified recombinant SjEDF- protein. Western blotting was used to analyze the immunogenicity and the expression level of SjEDF- at the different developmental stages. Results The SjEDF- gene was detected with a band of 405 bp in eggs, schistosomula, female and male worms. The recombinant protein （rSjEDF-） was expressed as inclusion bodies （Mr 20 000）. Western blotting analysis showed that the purified rSjEDF- protein was recognized by pooled sera of infected rabbits. The target protein was detected only in schistosomulum and adult worms. Conclusion The recombinant protein （rSjEDF-） shows certain immunogenicity, and is detected only in schistosomula and adult worms.

Key words: Schistosoma japonicum, Endothelial differentiation-elated factor-, Stage-pecificity, Immunogenicity