ABSTRACT
Objective To express the gene encoding mature protease of Schistosoma japonicum asparaginyl endopeptidase (Sj32) and evaluate the potential of the recombinant protein rSj32 in diagnosis of domestic animal schistosomiasis. Methods The DNA fragment encoding mature protease of Schistosoma japonicum asparaginyl endopeptidase was cloned with PCR from pET-28(a)/Sj32, and a recombinant plasmid was previously constructed in the laboratory, which contained the ORF of the gene encoding the pro-enzyme Sj32. The amplified DNA fragment was subcloned into pET-28a( + ) and the recombinant plasmid was transformed into E. coli BL21 (DE3) to express the mature protease of Sj32. Then the recombinant antigen (rSj32) was used in ELISA assay to diagnose schistosomiasis of mice, rabbits and water buffalo artificially infected. The detection effects of soluble Schistosoma japonicum egg antigen (SEA) , rSj32 and the recombinant 23 KDa membrane protein were compared. Results The recombinant antigen rSj32 with a molecular weight 41 KDa was successfully produced in E. coli BL21 ( DE3) and was purified with His Column with a yield of 25 mg/L E. coli culture. By using rSj32 as coating antigen in ELISA assay to detect the specific antibody in artificially infected mice, rabbits and buffalo, the sensitivities were 88.9% , 85.0% and 71.8% , respectively, the specificities were 100% , 96.7% and 96. 9% , respectively. There were no significant differences among the detection results of rSj32, SEA and rSj23. Conclusion rSj32 is a promising antigen for serological diagnosis of domestic animal schistosomiasis.