A strain of avian coronavirus of the GVII lineage capable of infecting African green monkey kidney cell lines (Vero) and chicken embryo fibroblast cell lines (DF-1)

The infectious bronchitis virus (IBV) belongs to the γ-coronavirus family and posing a serious threat to poultry health. Here, a single IBV strain, designated as IBV-250607GXCX, was isolated and identified from a poultry farm. S1 gene typing classified 250607GXCX as belonging to the genotype GVII-1 of IBV. Nucleotide sequence similarity and phylogenetic analyses revealed that 250607GXCX shares high sequence similarity and a close evolutionary relationship with I0636/16, suggesting that 250607GXCX may be the result of the long-term evolution of the parental strain I0636/16 in the Guangxi region. Recombination analysis showed that the S gene of 20250607GXCX did not undergo significant recombination during evolution, whereas the 1b, 3a, M, and N genes underwent recombination events with locally circulating strains. This study confirmed that 250607GXCX can efficiently infect Vero and DF-1 cells, exhibiting cell infection capacity and cell tropism similar to those of the Beaudette strain, and that this infectivity does not require passage through chicken embryos. Pathogenicity studies revealed that 250607GXCX is not lethal, that it primarily affects the respiratory tract of chickens, and that viral replication and shedding efficiency significantly decrease at 14 days post-infection. Receptor binding analysis showed that 250607GXCX and Beaudette have weak binding capacities for alpha-2,3-sialyltransferase, suggesting that there may be other accessory adhesion factors or secondary receptors assisting IBV cell invasion besides alpha-2,3-sialyltransferase. Overall, our study identified an IBV strain with good infectivity in cell lines and reduced pathogenicity, making 250607GXCX a promising tool for studying IBV invasion mechanisms and as a reverse genetic vaccine vector.