猪繁殖与呼吸综合征病毒北京分离株的ORF7克隆与序列分析

将北京地区猪繁殖与呼吸综合征病毒（ＰＲＲＳＶ） 分离株ＢＪ２ 和ＢＪ４ 的ＯＲＦ ７ 及部分３’端非编码区（ ＵＴＲ） 的ＲＴＰＣＲ 扩增产物克隆连接于ｐ ＧＥＭＴｅａｓｙ 质粒载体上，重组质粒经ＥｃｏＲ Ⅰ酶切鉴定后进行了双链测序。测定的基因序列与欧美标准毒株已知序列比较发现，ＢＪ２ 和ＢＪ４ 株与美洲ＶＲ２３３２ 株非常接近，在其长度为５５５ ｂｐ 的ｃＤＮＡ 序列中，仅与ＶＲ２３３２ 株分别相差１ 和２ 个核苷酸，其中ＯＲＦ ７ 的核苷酸序列与ＶＲ２３３２ 株同源性分别高达１００ ％ 和９９ ．４６ ％ ，其推导的氨基酸序列与ＶＲ２３３２ 株同源性分别为１００ ％ 和９９ ．２５ ％ ，３’ＵＴＲ 则完全相同；而与欧洲ＬＶ 株则有明显差异，其核苷酸序列同源性仅为６８ ．００ ％ 和６７ ．００ ％ ，推测的氨基酸序列同源性仅有６５ ．００ ％ 和６４ ．００ ％ ，且ＢＪ２ 和ＢＪ４ 株与ＬＶ 株相比缺失了ＫＫＳＴＡＰＭ 和ＡＳＱＧ 两段氨基酸序列，而３’ＵＴＲ 则比ＬＶ 株多出３８ ｎｔ 的一段特征性核苷酸序列。序列分析结果表明，ＢＪ２ 和ＢＪ４ 株属于同一基因型，且具有ＶＲ２３３２ 株的基因特点

Cloning, Sequencing and Analysis of the Putative N gene (ORF 7) of PRRSV Beijin Isolates

The putative nucleocapsid (N) protein gene (ORF 7) and partial 3' end untranslation region (UTR) of two isolates of porcine reproductive and respiratory syndrome virus (PRRSV), BJ 2 and BJ 4, were cloned into pGEM T easy vector and sequenced. Furthermore, the nucleotide sequence and deduced amino acid sequences of putative N protein from the two isolates were aligned with other reference PRRSV strains: European isolate LV and US isolate VR 2332. There were only 1 or 2 nucleotide substitutions within 555 bp cDNA sequence among the isolates BJ 2, BJ 4 and US isolate VR 2332, and displayed 100% and 99.46% homology in the nucleotide sequences, 100% and 99.25% homology in the deduced amino acid sequences of the putative N gene, respectably. However, their nucleotide sequences and amino acid sequences varied extensively from European isolate LV, numerous substitutions, deletions and insertions were distributed, and displayed 68% and 67% homology in the nucleotide sequences identity and 65% and 64% amino acid sequence homology only. Comparative sequence analysis indicates that the two isolates, BJ 2 and BJ 4, are belong to the same genotype and share the same genetic property of US isolate VR 2332.