Abstract: 【Abstract】 Objective To produce and purify egg yolk immunoglobulin against soluble egg antigen （SEA） of Schistosoma japonicum， and evaluate its specificity and sensitivity. Methods 25-week old hen was intravenously and subcutaneously immunized with SEA of Schistosoma japonicum for 4 times. Each hen was first immunized with 60 μg SEA and subsequent injections were performed at 10-day intervals with 30 μg SEA. IgY was extracted from eggs of hen 35 d after the first inoculation by WD（water-dilution） method， eggs from non-immunized hen were used as negative control. The protein concentration of IgY was measured by BCA method， and IgY was analyzed by SDS-PAGE and Western blotting. SEA-based ELISA was used to evaluate the specificity and sensitivity of the IgY. Results 61 mg IgY was extracted from one egg. The results of SDS-PAGE and Western blotting demonstrated that the IgY contained one major protein band with molecular weight of 130 000 and could be recognized by SEA. Specific IgY could be immediately detected by SDS-PAGE and ELISA in the eggs laid by the hens from 10 days after the first immunization. On day 31 after the primary immunization， the antibody titer reached 1∶1 600. 2.4 ng/ml SEA was detected by IgY based-sandwich ELISA， which indicated a high sensitivity of the purified IgY. Conclusion Anti-SEA IgY with high specificity and sensitivity has been obtained and purified.

Key words: IgY, Schistosoma japonicum, Immunodiagnosis, Circulating antigen