Research And Development Of Egg Yolk Immunoglobulin (IgY) Against Avian Infectious Bursal Disease Virus

Egg yolk antibody as an immunotherpeutics in veterinary clinical setting has been wildly utilized in the stockbreeding industry in China. And it has been wel-recognised that such a biotherapeutics has a potential of curing infectious diseases. However, poorly purified egg yolk antibodies were used in the clinical settings. Recently, many disadavantages have been reported, fat and other agents with complex molecular structure,which cause the swelling, hemorrhage, necrosis and severe anaphylaxis after administering of antibody into the animal tissues. Generally speaking, the limitations restrict the cosmically clinic use. The experimental objective of my project was to raise yolk antibody against avian infectious bursal disease virus and develop a protocol for purification in order to meet the clinical demands. The egg yolk increase maternal antibodies and was defatted in order to develop a serious of producing technics which can be suitable to the industrialized production and in accordance with the standard of national veterinarian biotherapeutics.Specific IgY were produced in hens immunized with four different immunogen rationals: (1) chick embryo tissue Inactivated vaccine;(2) bursa tissue Inactivated vaccine; (3) VP2 Genetic engineering vaccine; (4)VP2 Genetic engineering vaccine and bursa tissue inactivated vaccine mixed proportional. Preparation of the corresponding high price of egg yolk antibody,We find that the changing laws of antibodies in egg yolk and serum of laying hen are almost consistent, When two immunogen are used simultaneously, they can work in cooperation with each other.After exploring, four degreasing methods was established: PEG Precipitation, poloxamer- caprylic acid Precipitation, Water Diluting Method,water- caprylic acid Method. The crude egg yolk antibody can get a stable titer and good biological properties. But through comprehensive comparison, this test finally determin poloxamer as the precipitant: Concentration of 1.2% poloxamer,gauze filtration after the natural sedimentation, Concentration of 0.2% caprylic acid.The stability test of the egg yolk antibody indicate that, IBDV-IgY can maintain good stability at the environment of alkaline, neutral, weak acid, but antibody activity have greater losses at the environment of strong acid.When stored at 37℃. The antibody showed a poor stability. When stored at -20℃and 4℃, the antibody showed a good stability after 6 months. When stored at room temperature, the antibody did not have any alteration as well. When heated above 70℃, the antibody had a poor stability. The antibody activity reduced by 50% retention rate 8 hours after trypsin digestion,After exploring, the appropriate amount and the best therapeutic approach were optimised. Animal protection test results showed that IBDV-IgY antibody can effectively protect the chickens, chicken Intramuscular egg yolk antibody 1ml every day for the 1:32 titer Within 24 hours after virus attack, and use 3 days can protect more than 80%.Animal Cohabitation infection test results showed that IBDV-IgY antibody can 100% prevent the Cohabitation infection.In conclusion, this study prepare of specific IgY against avian infectious bursal disease virus, and examined its stability in vitro. It lay the foundation for the further clinical application.