Phylogenetic analysis on glycoprotein genome of rabies viruses in Yunnan,2012-2015

Objective To understand the molecular evolution characteristics of the glycoprotein (G) genes and epidemiological characteristics of 35 rabies virus strains isolated in Yunnan province from 2012 to 2015. Methods The brain tissue samples from sick dogs,suspected sick dogs in areas with high incidence of rabies and human brain tissue and saliva samples of rabies patients were collected in Yunnan to detect the viral antigen by using direct immunofluorescence assay(DFA). The viral RNA from positive samples was extracted. Coding region of G gene was amplified with reverse transcription polymerase chain reaction(RT-PCR)and sequenced. The phylogenetic tree was constructed by Neighbor-Joining methods of MEGA 5.0 software. Results The sequences of G genes of 35 rabies virus strains in Yunnan during this period were obtained. With the sequences of G genes of 11 rabies virus strains from Yunnan during 2006-2011 and 15 rabies virus strains from adjacent provinces and Southeast Asia countries,the phylogenetic analysis was performed. Forty-six rabies virus strains isolated in Yunnan belonged to two clades:China-Ⅰ(45 strains)and China-Ⅵ(1 strains). Clade China-Ⅰ virus circulated from 2006 to 2015. In this clade,10 strains isolated during 2006-2011 and 35 strains isolated during 2012-2015 were from 10 prefectural areas of Yunnan. The strains of clade China-Ⅰ were closely related to the strains from adjacent Sichuan,Guizhou and Hunan provinces. Clade China-Ⅵ virus was detected only in 2006,i. e. strain Tc06,which was closely related to the strains from Southeast Asia countries:Myanmar,Laos and Vietnam. Conclusion Clade China-Ⅰ rabies virus was widely distributed in rabies epidemic areas of Yunnan during 2012-2015,which was the predominant clade and had rapid spread potential. No clade China-Ⅱ,China-Ⅲ and China-Ⅵ viruses were detected again in Yunnan in recent years.