Abstract: 　Objective To improve SEA-ELISA, an immunodiagnostic assay for schistosomiasis. Methods Solu- ble egg antigen
SEA of Schistosoma japonicum was treated with sodium periodate (SP) in order to oxidate its glycosylated epitopes. ELISA using the treated SEA was then performed to detect specific antibodies to SEA in the sera of schistosomi- asis patients. Results Serum samples were tested by ELISA using SEA treated with sodium periodate (SP-SEA- ELISA), including 64 sera from cases with chronic schistosomiasis japonica, 119 sera from normal individuals in non-en- demic area, 34 sera from patients with clonorchiasis, 33 sera of paragonimiasis cases and 36 sera from patients with cysticer- cosis. The results showed that its sensitivity (98. 4%) was similar to that of the routine SEA-ELISA (100. 0%) (P> 0. 05) and the specificity is higher than that of the SEA-ELISA (P<0. 05). SP-SEA-ELISA showed a higher negative rate (89. 0%) for sera of schistosomiasis patients 12 months post-treatment than that of the SEA-ELISA (42. 1%). Conclu- sion Use of SP-SEA can increase the specificity of ELISA, reduce cross-reactivity with serum samples from cases infected with other parasites and improve its value in evaluating therapeutic efficacy.

Key words: schistosomiasis, sodium periodate, soluble egg antigen (SEA), ELISA