Characterization of three infectious bronchitis virus isolates from China associated with proventriculus in vaccinated chickens

Outbreaks of an avian disease in infectious bronchitis-vaccinated chickens in China have led to the characterization of coronaviral isolates Q1, J2, a nd T3, which were isolated from proventricular tissues of the affected youn g layer flocks. Serologic analysis revealed that they could induce high tit ers of infectious bronchitis virus (IBV) antibodies in inoculated specific- pathogen-free (SPF) chickens in indirect enzyme-linked immunosorbent assay but were not neutralized by antisera specific to the IBV serotype M41 and t he Australian T strain. In a pathogenicity experiment, the clinical signs a nd related gross lesions resembling these of field outbreaks were reproduce d in SPF chickens, and viruses were reisolated from the damaged tissues, in cluding trachea, proventriculus, duodenum, and cecal tonsil. Sequence data demonstrated the complete S1 amino acid sequences of these isolates were al most identical despite recovery from geographically different areas in Chin a and had 47.3%-82.3% similarity in comparison with the 47 published S1 seq uences. On the basis of genotyping and limited serology, the three isolates , which were responsible for field outbreaks of the disease, might be a new IBV variant.