Cloning and Sequence Analysis of Spike Protein Gene of Canine Coronavirus Giant Panda’s Isolate*

Spike (S) gene of Canine coronavirus giant panda’s isolate (CCV strain DXMV) was amplified and cloned into pGEM-T for sequencing. The complete length of spike gene of strain DXMV was 4362 bp, which encoded 1453 amino acids. The initiative 18 amino acids were signal peptide. The homologies of nucleic acid and amino acid of spike among strains of CCV were 40.2-99.5% and 15.9-99.0%, respectively. The variation mainly exist in front half second region of S gene, especially in the regions of 350-370, 439-478 and 1718-1818 nucleotide acids, while the region 1060-1700 nucleotide acids shows high conservative. Phylogenetic tree based on S gene and deduced amino acid sequence of 12 different strains of CCV showed that strain DXMV had closer relationships with wild strain K378，NVSL and US patent. There are 34 N-glycosylation sites in deduced S protein of strain DXMV and V54, but 33 for strain Insavc-l. Noticeably, the potential glycosylation site 566-568 was owned by DXMV and most virulent strains but not for weak virulent strains. Moreover, there were some differences in the hydrophobicity and antigenic index between DXMV and other strains of CCV. The effects of the differences in S protein on pathogenicity and immunogenicity should be further studied.