Genotype and pathogenicity of infectious bronchitis viruses isolated from proventriculitis cases

To study whether the infectious bronchitis virus(IBV) is the main causative agent of chicken proventriculitis,two IBV strains isolated from proventriculitis cases previously,CK/CH/HeB/2011/1 and CK/CH/HeB/2011/2,were chosed.Firstly,two IBVs were propagated in SPF embryonated chicken eggs,and proved to be far away from any foreign virus pollution.The S1 genes were cloned by RT-PCR,and the sequencing results showed that S1 gene length was 1 611 and 1 620 bp respectively.Two IBVs were further grouped into different genotypes,Mass and QX,through sequence alignment and phylogenetic analysis.To determine the pathogenicity of these two IBVs,two groups of 10 14-day-old SPF chickens were infected with diluted virus(106 EID50·mL-1) through intranasal route.All chickens in both groups showed respiratory symptoms.Till 10 d postchallenge,the mortality was 90% for both groups.The consistent pathological change in all chickens was characterized as interstitial nephritis,and no proventriculitis similar to clinical cases could be observed in any challenged chicken.The results suggested that multiple genotypes of IBV could be isolated from proventriculitis cases,and the studied two IBVs could not induce proventriculitis alone.