ACTIVE AND PASSIVE PROTECTION AGAINST VARIANT AND CLASSIC INFECTIOUS BURSAL DISEASE VIRUS-STRAINS INDUCED BY BACULOVIRUS-EXPRESSED STRUCTURAL PROTEINS

Infectious bursal disease virus (IBDV) is responsible for a highly imm unosuppressive disease in young chickens which causes significant econ omic losses to the poultry industry worldwide. The structural protein genes (VP2, VP3 and VP4) of a variant IBDV strain (GLS) were expressed in insect cells using a baculovirus expression system. Susceptible ch ickens vaccinated with a single dose of the recombinant IBD V antigens were completely protected against challenge with two variant strains of IBDV (GLS and Delaware), and partially protected against the standa rd challenge strain (STC). A booster dose of the recombinant antigens induced higher levels of neutralizing antibodies and afforded complete protection against both variant and standard virus challenges. Specif ic-pathogen-free hens vaccinated with a single dose of the same subuni t vaccine produced virus-neutralizing antibodies that were capable of passively protecting the progeny from infection with variant IBDV.