Characteristics of an emerging canine respiratory coronavirus in China.

Abstract

Canine respiratory coronavirus (CRCoV) is a prevalent pathogen implicated in canine infectious respiratory disease, yet information on its genomic characteristics and pathogenicity remains scarce. To address this situation, we investigated the genetic evolution and pathogenic potential of CRCoV strains circulating in China. Five complete CRCoV genomes (GenBank: PQ725948-PQ725952) were obtained from clinical samples, and phylogenetic analysis showed these strains formed a distinct genetic branch. The evolutionary trees for ORF1ab, HE, and S genes closely mirrored the full genome tree, indicating key roles for these genes in CRCoV evolution. Multiple unique amino acid mutations were identified in the ORF1ab, HE, S, M, and N proteins. Notably, molecular docking analysis suggests that mutations S158F and L161F in the HE lectin domain are associated with improved docking scores, indicating a potential increase in receptor-binding affinity. Consecutive nucleotide deletions in two non-coding regions between non-structural protein genes-which were also identified in strains of a Thai lineage (OQ621707.1-OQ621727.1)-were observed. A CRCoV strain (10⁶ TCID₅₀/mL) was isolated, and experimental infection confirmed its ability to induce pneumonia and tracheal cilia loss in dogs. These findings reveal the emergence and unique genetic diversity of a novel CRCoV variant in China, highlighting the need for ongoing epidemiological surveillance.