犬瘟热病毒疫苗免疫逃逸株的血凝素基因变异研究

为了弄清是否有新基因型犬瘟热病毒出现,对山东省不同地区的免疫水貂、狐狸和犬进行了犬瘟热病毒检测,扩增了病毒核衣壳基因和血凝素基因(H),并对13个犬瘟热病毒山东株(8株貂源,2株狐狸源,3株犬源)血凝素基因进行了测序。结果表明,13个犬瘟热病毒山东株之间H基因核苷酸同源性为99.1%~100.0%,均为Asia-1型,这也是我国目前水貂犬瘟热病毒唯一的基因型。与2012年之前的犬瘟热病毒中国分离株及疫苗株相比,13个毒株H基因有4个氨基酸的一致性变异,即P200S、M263I、I542N和Y549H,N-糖基化位点比Onderstepoort株多6或7个,比CDV3株多3或4个。抗原性分析表明,与疫苗株相比,13株山东株在540-549位氨基酸出现一个新的抗原区域,210-230,327-347位的抗原区域也与疫苗株不同,这些变异可能是我国貂狐犬瘟热免疫失败的原因。

Sequence Analysis of the Hemagglutinin Gene of Canine distemper virus from Vaccinated Dogs,Minks and Foxes

In order to understand whether new genotype emerged,we detected Canine distemper virus(CDV)in immunized dogs,breeding foxes and minks in different regions by amplification of nucleocapsid(N)and hemaggluti-nin(H)gene.13 strains from CDV-positive cases(8 minks,2 foxes and 3 dogs)were sequenced.The results showed that the 13 Chinese strains shared 99.1 %-100.0% nucleotide identity.Compared with those of other Chinese CDV strains isolated before 2012,four consistent amino acid changes,P200S,M263I,I542N and Y549H,were observed in the H coding sequence of CDV isolated from vaccinated animals,which contribute to an additional N-glycosylation site and antigenic epitope.All of the strains obtained from 13 samples were characterized as genotype Asia-1 accord-ing to the sequence analysis of the complete H gene,which was the sole genotype in minks in China.These findings provide a comprehensive understanding of current immune failure and the molecular epidemiology of CDV in China.