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

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.