马传染性贫血病毒第19、26代驴胎皮肤细胞弱毒前病毒DNA全基因序列分析

不同代次马传染性贫血驴胎皮肤细胞弱毒(Fetal donkey dermal virus,FDDV)的免疫保护效果各不相同,只有第10～15代驴胎皮肤细胞弱毒具有良好的免疫保护效果,可作为疫苗使用,继续传代则疫苗的保护率下降。为确定有、无免疫保护效果的FDDV在基因水平上的差异,本实验对无免疫保护效果的第19、26代驴胎皮肤细胞弱毒前病毒DNA进行了全基因序列测定,并与已测序的疫苗毒株进行序列比较。第19代和第26代FDDV全基因核苷酸序列同源性高达99.5%,与疫苗毒株全基因核苷酸序列的同源性分别为96.9%、96.7%。LTR是EIAV在细胞传代中变异最显著的区域,第19、26代FDDV的LTR与疫苗毒的LTR同源性仅为89.6%、89.3%。马传贫病毒的gag基因高度保守,第19、26代FDDV与疫苗毒株的gag基因推导氨基酸序列仅有2个氨基酸不同。第19、26代FDDV与疫苗毒株的pol基因、env基因的推导氨基酸序列的同源性分别为98.9%、98.8%、93.7%、93.6%。由序列比较结果可以推断,第19代、第26代FDDV不具有免疫保护效果的主要原因可能是由于LTR和env基因的变异,导致病毒复制能力下降或免疫原性丧失,不能诱导机体产生良好的免疫反应。

Cloning and sequencing of the full genome of equine infectious anemia virus provirus DNA

Immune protection of fetal donkey dermal cell virus(FDDV)against equine infectious anemia is affected by the generations of virus passages.Only the 10th to 15th generations could be used as effective vaccine,and higher generations of passage render the vaccine nonprotective.In order to investigate the difference between the virus genomes of the effective vaccine and nonprotective FDDV,the provirus DNA of the 19th and 26th generations of FDDV were amplified by PCR,cloned,and sequenced.The results showed that the full genome nucleotide sequence of the 19th and 26th generations of FDDV shared 99.5% homology,while both strains shared 96.9%,96.7% homology to FDD vaccine strain.LTR was the prominent region of mutations in full genome during cell culture passages,which showed only 89.6%,89.3% homology respectively between the 19th and 26th generations of FDDV and the FDD vaccine strains.The gag gene of EIAV is highly conserved with only two amino acids changes between the virus strains.In comparison,the pol and env genes are less conserved between the vaccine and the 19th and 26th generation strains,with amino acids sequence similarities of 98.9%,98.8% for pol gene,and 93.7%,93.6% for env gene.We concluded that the loss of immune protection of the 19th and 26th generations of FDDV could result from reduced virus replication ability caused by mutations in the LTR and env gene.