Isolation and characterization of bovine coronavirus variants with mutations in the hemagglutinin-esterase gene in dairy calves in China.

backgroundBovine coronavirus (BCoV) is a causative agent of enteric and respiratory diseases in cattle and is responsible for severe economic losses. Recently, a novel BCoV variant with 12-nucleotide deletion or insertion in the hemagglutinin-esterase (HE) receptor-binding domain (RBD) has emerged. However, the biological consequences of these deletions/insertions and the prevalence of these variants remain unknown. Here, 47 diarrheal and 47 nasal swab samples were collected from five cattle farms in various Ningxia, China regions to detect and isolate BCoV.

resultsEleven complete HE genes and eight complete S genes were amplified from 34 BCoV-positive samples using RT-PCR. Eight BCoV strains were successfully isolated using HRT-18 cells, and four underwent genome sequencing. Three HE genes contained a 12-nucleotide insertion in the RBD, and a single HE gene contained a novel 12-nucleotide deletion. Phylogenetic analysis of genomes revealed that these HE-deletion/insertion variants do not share a common most recent ancestor with those reported from the US. Molecular docking results showed that the insertion of four additional amino acids between F211 and L212 increased the affinity of HE protein to O-acetylated sialic acid, which may be favorable for virion-particle attachment. Growth kinetics suggest that the HE-deletion variant had a non-cytopathic effect and lower virus titer.

conclusionsThese findings suggest that BCoV HE deleted/inserted variants are prevalent in cattle and exhibit various biological characteristics. We should be alert to these HE-variants with insertions or deletions in the RBD, which may increase the possibility of interspecies transmission.