Genetic and Pathologic Characterization of a Novel Recombinant TC07-2-Type Avian Infectious Bronchitis Virus

Avian infectious bronchitis viruses (IBVs) with the TC07-2 genotype have spread rapidly in East Asia since they were first reported in China in 2007. In 2015, an IBV with the TC07-2 genotype (designated KrD1515) was isolated from layer chickens with severe respiratory symptoms in Korea. In the present study, the full-length open reading frames of the spike (S) and nucleocapsid (N) genes of the virus were sequenced and analyzed. S1 gene phylogenetic analysis revealed that the KrD1515 virus clustered with viruses with the TC07-2 genotype, whereas N gene phylogenetic analysis revealed that the KrD1515 virus clustered with Korean IBVs, but not with Chinese TC07-2 IBV. When 7-day-old specific-pathogen-free chickens were inoculated with the KrD1515 virus, they developed severe respiratory symptoms and tracheal lesions. However, there were no other clinical symptoms or pathologic lesions in other tissues. The virus was shed from the trachea for at least a week and from the cloaca for only a day. Our findings suggest that the KrD1515 virus is a recombinant virus between a Chinese TC07-2 IBV and a non-TC07-2 Korean IBV and engages in respiratory tropism in chickens.