Isolation And Attenuation Of Nephropathogenic Avian Infectious Bronchitis Virus W Strain And Sequencing Of The S1 Gene

A virurent nephropathogenic avian infectious bronchitis virus (IBV) strain tentatively named as W strain was isolated in China. The strain was identificated systematically through chicken and embryo infection test, pathogen identification, virus interaction test, morphology test, serological identification and virulence assay. The virus was passaged from generation to generation in chicken embryo. After security and immunology test a low virulent strain designated as W93 was abtained. The EID50 of the embryo fluid infected with W93 strain was 107.5/0. 1mL compared with other strain of 106.0EID50/0. 1 mL about. The W93 strain possessed well security and immunogenicity for all age of chickens.It can be used as urgent vaccine after IB breaking out, as can reduce the fatality rate from 15%~50% to 0. 6%~2% . One pair of primers for amplifying the S1 gene of avian infectious bronchitis virus (IBV)had been designed, with which the predicted 1.62 kb fragment had been amplified via RT-PCR from Nephropathogenic Strain W93. The S1 gene of Nephropathogenic Strain W93 was sequenced and compared with standard strains such as H52, M41,H120 and BEAU. The results showed that the homologies of nucleic acids between W93 strain and H52,M41,H120 and BEAU strains were 96. 8 %, 97. 1 %, 96. 9 % and 96. 8 % respectively. The high homology of the S1 gene of Nephropathogenic Strain W93 with those of other IBV standard strains had been proved.