Phylogenetic Analysis of the Haemagglutinin Protein Gene of Canine Distemper Virus from Giant Panda and Other Animals in China
To characterize the genetic variation of haemagglutinin (H) protein gene of strains of canine distemper virus (CDV) -GP, LP and LIU strains-from giant panda, lesser panda and dog in China, we conducted nucleotide sequence analysis of the H gene. The 1946 nt of the complete H gene sequences of the three strains showed that the largest open reading frame (ORF) encoding a protein of 607 amino acid residues started at the ATG at position 21～23 and extended to a termination codon TGA at position 1?842～1?844. The deduced amino acid sequences of the H protein of the Chinese strains were compared with those of other CDV strains extracted from the GenBank or EMBL database. It showed that there are eight or nine potential sites for asparagine -linked glycosylation in the H proteins of 16 field isolates, in contrast to four or seven in those of the vaccine strains-onderstepoort and convac strains. The potential N-linked glycosylation site at position 309-311 amino acids is unique to all field isolates, thus, the extra glycosylation sites may influence antigenicity of the viruses. Phylogenetic analysis of the eighteen CDV sequences based on complete sequence of the H gene showed that there are different genotypes of CDV, all the sixteen field isolates group together, within this group, GP, LP, Mink; 2?544, 404, 4?513, Dandog; A92-6, Leop, Jave, Racc, Amedog; Hama, Ueno and Green, LIU form five lineages respectively. The two vaccine strains are distinct from all of field isolates and form another group.