Molecular Characterization of the FCoV-like Canine Coronavirus HLJ-071 in China

Abstract

Background According to differences in antigens and genetic composition, canine coronavirus (CCoV) consists of two genotypes, CCoV-Ⅰ and CCoV-Ⅱ. Recently, CCoVs with mutant variations have been found to be pantropic and pathogenic in dogs. Results In this study, we isolated a CCoV, designated HLJ-071, from a dead 5-week-old female Welsh Corgi with severe diarrhea and vomiting. Sequence analysis suggested that HLJ-071 bears a complete ORF3abc when compared with classic CCoV isolates (1–71, K378 and S378). In addition, a variable region was located between the S gene and the open reading frames (ORF) 3a gene, in which HLJ-071 has a deletion of 104 nucleotides (nts) when compared with classic CCoV strains 1–71, S378 and K378. Phylogenetic analysis based on the S gene and complete sequences showed that HLJ-071 is closely related to Feline Coronavirus (FCoV) II. Recombination analysis suggested that HLJ-071 originated from the recombination of FCoV 79-1683, FCoV DF2 and CCoV A76. Finally, cell tropism experiments suggested that HLJ-071 is able to replicate in canine macrophages/monocytes. Conclusion The present study involved the isolation and genetic characterization of a variant CCoV strain. The spike protein and ORF3abc of CCoV might play a key role in viral tropism, which could affect replication in monocyte/macrophage cells. This will provide essential information for further understanding the evolution of CCoV in China.