[Dynamic observation of chicken egg yolk antibodies against soluble egg antigen of Schistosoma japonicum obtained by two immunization routes]

Abstract

Objective: To observe the dynamic changes of the specific chicken egg yolk antibodies (IgY) against soluble egg antigens (SEA) of Schistosoma japonicum by two immunization routes.

Methods: Seven New Zealand rabbits were infected with S. japonicum cercariae (1500 per rabbit). After 42 days the rabbits were sacrificed to collect eggs and prepare SEA. Two groups each with 3 healthy hens were intravenously and subcutaneously immunized with 50 microg SEA, respectively. All hens received five immunizations by the same dose of antigen, with 2-week interval for the first two doses, and 4-week interval for the rest doses. Hen eggs were collected at pre-immunization and every two weeks after the first immunization. Crude IgY was extracted from egg yolk by water dilution method, and were analyzed by SEA-based ELISA, then purified by using EGG stract IgY Purification System from the 8th to 18th week after the first immunization. IgY concentration was determined by A260/A280 ratio. The expression of IgY was detected by agarose double diffusion method and SEA-based ELISA. The characteristics of IgY was analyzed by SDS-PAGE and Western blotting.

Results: The titer of IgY reached a peak at the 8th week in the intravenous group (A492 = 1.28) and at the 12th week in the subcutaneous group (A492 = 0.78), respectively, and maintained at a high level in the intravenous group until the 18th week after the first immunization. The concentration of purified IgY was about 6.5-9.0 mg/nml. Agarose double diffusion method and SEA-based ELISA demonstrated that the peak titer of IgY in the intravenous group was 1:16 and 1:51200, respectively. SDS-PAGE demonstrated that IgY contained two major protein bands (Mr 25,000 and 68,000). IgY purified from immunized egg yolk specifically reacted with SEA.

Conclusion: The intravenous method is superior than the subcutaneous injection method in obtaining a high level of egg yolk antibodies against SEA of Schistosoma japonicum, and the purified IgY shows better specificity.