Abstract: 　Objective To sub-clone and express the gene encoding Schistosoma japonicum calcium-binding protein (SJE16) and study its immunological response. Methods The specific primers were designed according to the expressed sequence tags(ESTs) sequence, which was used for amplification of the encoding sequence from the cDNA clone containing SJE16. The gene was subcloned into pGEX4T-l plasmid and expressed. The rSjE16 was tested for its immunological response by ELISA. Results The gene encoding Schistosoma japonicum SJE16 was cloned and expressed successfully. The immuno-genicity and diagnostic potential of rSjE16 were investigated. It was demonstrated by immunoassay in rabbits that the specificity and sensitivity of the test were 94.1% (16/17) and 88. 2% (15/17), respectively, and the level of antibody liter of the untreated group reached a peak at 9 - 11 wk post infection and maintained high at least for 21 wk post infection, while the antibody level in the treated group rapidly decreased to pre-infection level in 11 wk after treatment. In human, the specificity of the test was 98.3% (57/58); the sensitivity of acute and chronic patient serum assay was 85.5% (53/62) and 70.2% (40/57), respectively. Conclusion The recombinant protein of SjE16 (rSjE16) was acquired. It can be recognized by the sera from schistosomiasis patients, and the level of antibodies decreased quickly after treatment in experimental rabbits, which implicates the potential value for the evaluation of chemotherapy and detection of active infection.

Key words: Schistosoma Joponicum, calcium-binding protein, immunodiagncsis