| Avian infectious bronchitis virus (IBV), a member of Coronaviridae ,could cause a highly infectious, contagious and pathogenic in chickens, which mainly invaded chicken respiratory, urogenital and digestive systems. IBV could cause respiratory disease and eggs production losses and has a high rate of mortality, resulting in great economic losses to the poultry industry worldwide. There are more than 20 kinds of serotypes of different IBV strains, but there was only a little cross-protection between them,causing disease outbreaks immune failur. For this reason it is important to search safety and efficacy vaccine strains.IBV genome consists of a single-stranded sense RNA encoding three structural proteins, integral membrane (M) glycoprotein, phosphorylated nucleocapsid (N) protein, spike (S) glycoprotein and other proteins. S glycoprotein is posttranslationally cleaved into amino-terminal S1 and carboxyl-terminal S2 subunits by cellular proteases. S1 protein involves in infectivity, contains virus-neutralizing epitopes, serotype-specific sequences and hemagglutinin activity. It is important to analysis the S1 gene in molecular level.In the January of 2008, respiratory signs were observed in the chicks of a layer farm in Cangzhou, Hebei province. Necropsy of the dead chicks revealed that the kindey was swollen and distended with uric acid crystals. The ?ocks was vaccinated with H120 vaccine. Kidneys and tracheas were collected for virus isolation. An IBV virus was identified by viral interference test, HA test, animal regressive research, cross-neutralization and RT-PCR. The virus was designated 0801 strain.The date of chicken embryo cross-neutralization showed that the coefficient of relationship(R) between 0801 strain and Ma5, W93, H120, M41 and H52 strain are 80.7%, 67.7%, 73.3%, 54.0% and 70.8%, respectively. This indicated that the 0801 strain and Ma5 vaccine strain belong to the same serotype.( when R>80%, the two strains are the same serotype; when 25% |
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