猪繁殖与呼吸综合征病毒YA株ORF5基因的克隆与序列分析

Cloning and Sequences Analysis on ORF5 Gene of Porcine Reproductive and Respiratory Syndrome Virus Strain YA

以猪繁殖与呼吸综合征病毒 (PRRSV)YA株为材料 ,采用RT -PCR扩增其ORF5基因全长cDNA并进行序列测定和比较分析。结果YA株ORF5基因cDNA编码区长 6 0 3bp ,可编码 2 0 0个氨基酸残基。与欧洲型代表株LV株、美洲型代表株VR - 2 332株在氨基酸水平上的同源性分别为 5 8%和 90 % ,与国内首株分离株 (CH - 1a)的同源性高达 95 % ,推测YA株属于美洲型。根据YA株ORF5基因编码的氨基酸序列 ,与具有代表性的 12株美洲型毒株和 2株欧洲型毒株绘制进化系统树 ,结果也显示YA株与美洲型分离毒株的遗传关系较近 ,而与欧洲型毒株的遗传关系较远。进一步采用序列分析软件对推导的氨基酸进行比较分析 ,发现YA株ORF5编码的E蛋白存在 5个潜在的N -糖基化位点 ,6个抗原位点 ,其糖基化位点的数目及抗原位点的分布与其它美洲型毒株均存在一定程度的差异 ,但

The cDNA encoding envelope protein (E or gp5) of porcine reproductive and respiratory syndrome virus(PRRSV) strain YA was amplified by RT-PCR. The cDNA fragment was further cloned and the complete sequences was determined. The results showed the cDNA of ORF5 was 603 bps,encoding 200 amino acids. Comparied with the ORF5 gene of typical North American strain (VR-2332 strain) and European strain (LV strain), it was found that there was 90% and 58% homology at amino acids level respectively. It indicated that the PRRSV strain YA belongs to North American type. The phylogenetic tree based on deduced amino acids of the ORF5 gene of PRRSV YA strain, 12 typical North American strains and 2 typical Europe strains PRRSV was constructed. There existed significant relationship between the YA strain and North American strains. Molecular characterization of the deduced amino acids were performed with the aid of several software packages. The results showed that there existed 5 potential N-glycosylation sites and 6 potential antigenic sites in the ORF5 of PRRSV YA strain. Although there existed many mutants in the ORF5 of PRRSV YA strain, the three known epitopes were relatively conserved.