Abstract
Three out of 109 mixed lung and tracheal tissue extracts originating from Korean dogs tested positive for infection with canine respiratory coronavirus (CRCoV) of Coronaviridae group 2. The three CRCoV-positive samples were found to be competent for viral propagation and isolation, using human rectal tumor cells (HRT-18), and the structure and nonstructure proteins encoded in the 3'-end of the CRCoV genome were sequenced. The small open reading frames situated between the spike and envelope genes of the three Korean CRCoV isolates were found to encode three nonstructural proteins (4.9 kDa, 2.7 kDa, and 12.8 kDa in size), as were the British (CRCoV G9142) and Italian (CRCoV 240-05) strains. Comparison of the deduced amino acid sequences of the spike protein in the CRCoV and bovine coronavirus (BCoV) strains revealed twenty sequence variations. The predicted spike protein of CRCoV contained 20 or 21 N-glycosylation sites, whereas that of BCoV contained 19 sites. Phylogenetic analysis of the spike gene from eight CRCoV and six BCoV strains, performed using the neighbor-joining approach, allowed us to classify into two clades (CRCoV and BCoV) and three Korean strains (CRCoV-K9, -K37, and -K39) related to the Japanese strain 06/075.