Pathogenic Antigenic and Molecular Characterization of the Very Virulent Strain(Gx) of Infectious Bursal Disease Virus Isolated in China

摘要

The very virulent infectious bursal disease virus (vvIBDV) strain Gx was isolated from a poutl-try farm in Guangxi Province, China, during 1996. The mortality in the infected flock was 80% and occurred5 days after immunization with serotype I IBD vaccine. The results of antigen-capture ELISA (AC-ELISA),pathogenicity testing, cloning and sequence analysis of the VP2 gene showed that the deduced amino acid se-quence of strain Gx VP2 was the same as vvIBDV UK661, which is considered as a reference strain for Europe-an vvIBDVs. The antigenicity of the Gx strain was the same as an European vvIBDV strain 849. The EID50 of Gx virus was 10-8. 25/0. 2 ml, and the mortality was 64 % when 4 week-old SPF chickens were challenged atdosage of 2 × 103 EID50. We have demonstrated that the IBDV strain Gx isolated in China is vvlBDV according to European standards.