摘要：
Objective To investigate the molecular characteristics of H5 subtype avian influenza viruses (AIV) in Weining, Guizhou Province. Methods Nine representative strains were randomly select-ed from H5 subtype AIV that were identified by real-time PCR in Weining, Guizhou Province from 2015 to 2017. Nucleic acid was extracted from each sample and hemagglutinin (HA) genes were amplified and then sequenced. Homology, genetic evolution and the sites related to pathogenicity, receptor binding regions as well as potential glycosylation of H5 AIV were analyzed by bioinformation software. Results Homology analysis revealed that there was 96. 1%-99. 9% and 95. 7%-100% similarity among the nine strains in nu-cleotide and amino acid of HA gene, respectively. These strains belonged to two branches, H5-1 and H5-2. The cleavage site motifs were PLREKRRKR↓GLF for five strains in H5-1 branch and PQRERRRKR↓GLF for four strains in H5-2 branch, which made them high pathogenic. QSG and QRG at the key receptor bind-ing sites were found in H5-1 and H5-2 branch strains, respectively. They were responsible for receptor bind-ing specificity of AIV. Mutations of 138Q, 139G and 53K were all detected in the nine strains. 129K, 189T, 140K and 282V mutations were discovered in the five strains of H5-1 branch, while 189N, 140M and 282I mutations were found in the four strains of H5-2 branch. Results of the glycosylation motif analysis showed that six sites were conservative, but there was an addition of 124NHT site in two strains of H5-2 branch isolated in 2017. Conclusion Two high pathogenic H5 subtypes of AIV could be epidemic in Wein-ing, Guizhou Province during 2015 to 2017. Although H5 subtype AIV did not possess specific receptor binding regions like human influenza viruses, they were in continuous variation with an increase in glycosyla-tion motifs, which might enhance their virulence and pathogenicity to human beings. Hence, surveillance and study on the molecular properties of H5 subtype AIV should be strengthened.%目的 了解贵州省威宁H5亚型禽流感病毒的分子遗传特征,为禽流感病毒的研究与防控提供依据.方法 对选取的9 株 H5 亚型禽流感毒株标本进行基因组的提取、血凝素基因(hemagglutinin, HA)的扩增和测序,运用生物信息学软件分析HA基因的同源性、遗传进化、致病相关位点、受体结合关键位点和糖基化位点变异情况.结果 贵州省威宁2015—2017年9株H5亚型AIV的HA基因核苷酸和氨基酸同源性分别为96. 1% ～99. 9%和95. 7% ～100% ,分属于H5-1 和H5-2两大分支. H5-1 分支中5 株毒株裂解位点均为 PLREKRRKR↓GLF,H5-2 分支中4 株均为PQRERRRKR↓GLF,全部属于高致病性毒株.受体结合关键位点H5-1分支中5 株均为QSG,H5-2分支中4株均为 QRG,仍全部为禽流感病毒特异性受体结合区. 9 株毒株受体结合区均发生了138Q、139G和53K的突变,其中H5-1分支中5株毒株均存在129K、189T、140K和282V的突变,H5-2分支中4株均存在189N、140M和282I的突变. 9株毒株6个糖基化位点较稳定,但2017年H5-2分支中的2株毒株存在一个糖基化位点124NHT的增加.结论 贵州省威宁2015—2017年H5亚型禽流感病毒可能存在两种型别的流行,均属于高致病性禽流感病毒,虽不具有人源流感病毒特异性受体结合区,但病毒存在持续不断地变异,且糖基化位点有增多趋势,存在毒力增强和感染人的风险,故应加强监测与研究.
