Objective To observe the protective immunity induced by the nucleic acid vaccine of 21.^7 kDa membrane protein molecule of Schistosoma japonicum Chinese mainland strain (SjC 21.^7) in BALB/c mice. . Methods. A pair of primers (P1 and P2) was synthesized according to the DNA sequence of the SjC21.^7. The ORF sequence of SjC21.^7 was amplified by PCR, and the Kozark sequence was added to the position of initiator. The gene fragment was inserted into the eukaryotic expression plasmid pcDNA3.^1 to form the recombinant plasmid SjC21.^7-pcDNA3.^1. Forty-eight BALB/c mice were divided into three groups: control, test and boost. Each mouse was injected in quadriceps femoris with plasmid pcDNA3.^1 (control) or recombinant plasmid SjC21.^7-pcDNA3.^1 (test, boost); for the boost group, with additional P35-pcDNA3.^1 and P40-pcDNA3.^1. All mice were immunized three times with an interval of 2 weeks, challenged each with 45 cercariae of S.^japonicum at the 30th day after final immunization. At day 45 after challenge,all mice were sacrificed, the numbers of worms and hepatic eggs were counted. Antibody level in the sera of mice before and two weeks after immunization was determined with ELISA. The expression of the target gene in quadriceps femoris was observed with immunohistochemistry. . Results . The immunohistochemistry analysis showed that there were specific antigens expressed in the local tissue of the test group mice. There was specific IgG in the serum of partial mice in test and boost groups. Compared with the control group, the worm reduction rate was 29.^9% and its egg reduction rate 13.^8% in the test group; 31.^9% and 28.^0% respectively in the boost group. The egg reduction rate in the boost group was higher than that of the test group (P

Objective To investigate the value of mix recombinant antigen in schistosomiasis diagnosis. Methods The recombinant antigens of SjC23 (HD),SjC21.7 and SjCMP10 were expressed in vitro and purified by the affinity chromatography method. The efficacies of soluble egg antigen (SEA),single recombinant antigen and mix recombinant antigen for schistosomiasis diagnosis by Enzyme-linked Immunosorbent Assay were compared. Results The diagnostic efficacy was the same when the antibody IgG of the same group sera of schistosomiasis was detected by different quantities of 2.5 ?g/ml and 7.5 ?g/ml of SEA immobilized on microplate, and their absorbency A was the same, but there was a significant difference in the diagnostic efficacies between single recombinant antigen and mix recombinant antigen when the antibody IgG of the same group sera of schistosomiasis was detected by the same quantity of single recombinant antigen or mix recombinant antigen immobilized on microplate, the absorbency A of mix antigen reacted with the sera of schistosomiasis was significant higher than that of the single recombinant. The positive rates were very similar when 39 sera of acute schistosomiasis,80 sera of chronic schistosomiasis and 27 sera of advanced schistosomiasis were detected by SEA or mix recombinant antigen by ELISA in the same time. No cross-reaction presented when 20 clonorchiasis sera were detected by the mix recombinant antigen and no false positive presented when 40 of healthy sera were detected by the mix recombinant antigen. Conclusion The schistosomiasis diagnostic method by using the mix recombinant antigen has been established, which is helpful for improving the efficacy of schistosomiasis diagnosis.