[Analyses on the isolation and characterization of canine rabies virus isolates in Henan].

OBJECTIVE: To analyze the genetic characteristics of two rabies virus isolates from Henan province and to compare their relations hip with known rabies virus isolates and vaccine strains.

METHODS: Rabies viral antigens were detected in 100 canine brains by immunofluorescence assay method. Rabies virus was isolated through inoculating the suspensions of positive brains into suckling mice. N gene and G were amplified by RT-PCR and sequenced. Phylogenetic trees were constructed for the analysis on genetic characteristics of rabies virus.

RESULTS: Two rabies virus strains were isolated (Henan Hb1 and Henan Sq1). Data from sequential comparison revealed that the nucleotide and amino acid identities of N and G gene between the two isolates were 99.3% and 98.9%, and 98.7% and 98.4% respectively. The two isolates were more closely related to CTN, with the homogeny of N gene and G gene as 89.1% and 85.6%-85.7% at the nucleotide level, but 97.6%-98.0% and 92.3% at the amino acid level respectively, than to other vaccine strains. When comparing with other known viruses including Chinese isolates, the two stains shared closer identity with the isolates from Indonesia, and the rates of homogeny of N and G gene were 92.1%-93.2% and 91.9%-92.1% at the nucleotide level, 97.5%-98.6% and 96.0%-96.2% at the amino acid level, respectively. Data from the deduced amino acid sequences revealed that some amino acid residues including the residues in the N and G antigenic sites were substituted in the two isolates. Furthermore, phylogenetic analysis showed that the two isolates were also more closely related to the strains from Indonesia and vaccine strain CTN than to any other known street viruses and vaccine strains.

CONCLUSION: Both Henan Hbl and Henan Sql belonged to genotype 1. However, the N and G gene diverged from known street viruses and vaccine strains at either nucleotide level or amino acid level.