ABSTRACT
A new subunit vaccine against infectious bursal disease (IBD) was developed; the antigen used in the vaccine was expressed by a new engineering strain, E. coli BL21/pBV220-VP2. The study on the production and use of the vaccine was performed. The results showed that the recombinant VP2 was water-soluble and demonstrated natural antigen activity in vitro. The antibody induced by rVP2 subunit vaccine could protect chickens from challenges of IBDV strains, both BC 6/85 and JZ 3/02. The vaccine, in which the VP2 AGP titre is 1:4, would be enough to protect SPF chickens of 19-day-old, but seemed to be relatively lower to protect commercial Avian Broilers under 10-day-age. In field study, Avian Broilers were vaccinated with rVP2 subunit vaccine of 1:16 AGP titre at the age of 7 days. The protection rate was varied from 72% to 95% in different chicken farms. To study the method of serological evaluation, antibody respond to vaccination had been detected with three kinds of tests. The correct ratio of detection decreased in the order of VP2-based ELISA, AGP test, and virions-based ELISA, if the result of IBDV detection was used as standard of judging. Correlation coefficient between the OD values of VP2-based ELISA and the virions-based ELISA was 0.782. The results will make it possible for the vaccine to be produced commercially and used in poultry industry in large scale.
Subject(s)
Birnaviridae Infections/prevention & control , Birnaviridae Infections/veterinary , Chickens/immunology , Infectious bursal disease virus/immunology , Poultry Diseases/prevention & control , Viral Structural Proteins/immunology , Viral Vaccines/pharmacology , Animals , Antibodies, Viral/immunology , Birnaviridae Infections/genetics , Birnaviridae Infections/immunology , Chickens/virology , Enzyme-Linked Immunosorbent Assay , Escherichia coli/genetics , Infectious bursal disease virus/genetics , Poultry Diseases/genetics , Poultry Diseases/immunology , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Recombinant Proteins/pharmacology , Vaccines, Synthetic/genetics , Vaccines, Synthetic/immunology , Vaccines, Synthetic/pharmacology , Viral Structural Proteins/genetics , Viral Vaccines/immunologyABSTRACT
The objective of the present study was to investigate the feasibility of a subunit vaccine and a live bacteria vaccine to protect chickens against infectious bursal disease virus (IBDV) infection. The gene for VP2 of a new wild-type very virulent IBDV (vvIBDV) strain was cloned into an Escherichia coli expression system. Following expression, the recombinant VP2 and the induced expression bacteria were used to vaccinate chickens against virulent IBDV (vIBDV). Three weeks after the vaccination, chickens were inoculated with IBDV strain BC 6/85 by intranasal route or eyedrop route, prior to challenge anti-IBDV serum antibody was detected by AGP. All chickens vaccinated with recombinant VP2 could be detected anti-IBDV antibody. The subunit vaccine of recombinant VP2 conferred protection for 90--100% chickens, live bacteria vaccine of recombinant VP2 conferred protection for 85.7% chickens. The results indicate that E. coli BL 21/pET 28 a-VP2 could be used to develop recombinant VP2 vaccine against infectious bursal disease in chickens.
