采用RT-PCR方法自猪繁殖与呼吸综合征病毒基因组分离出核衣壳蛋白基因(D 7)，克隆到pMD18一T载 体构建成重组质粒pMD18N并进行测序比较，结果表明，所克隆的核衣壳蛋白基因序列与PRRSV美洲型ATCC VR．2332株的同源性为100％，表明off 7是PRRSV 基因组内很保守的序列：将of 7亚克隆到原核表达载体 pGEX．KG，构建成重组质粒pGEX—KGN，用pGEX—KGN转化表达菌株BL21，经SDS-PAGE和Western-blot分 析表明：克隆在谷胱苷肽转移酶(Glutathione S-transferase(GST)下游的核衣壳蛋白基因与GST获得了高效融 合表达，表达的融合蛋白GST-N 分子量约为41kDa，并且有免疫学反应活性；这为猪繁殖与呼吸综合征的血清 学诊断方法的建立打下了基础。

The nucleocapsid protein gene(orf 7)of Porcine reproductive and respiratory syndrome virus(PRRSV)was isolated from PRRSV genome by RT PCR．The gene was cloned into pMD 1 8一T vector,the recombinant plasmid pMD1 8N containing orf 7 was sequenced and compared with other PRRSV isolates．The result shown that the homologies between the cloned orf 7 and America type PRRSV ATCC VR一2332 reached 100％，the orf 7 was highly conservative sequence in PRRSV genome． The orf 7 was subcloned into prokaryofic expressing vector pGEX—KG，the recombinant plasmid named pGEX—KGN was constructed．The pGEX—KGN was used to tran sfo rnl into E colf BL21．Th e results of SDS—PAGE an d W estem—blot indicated that the nucleocapsid protein gene cloned in downstream of Glutathione S—tran sferase(GST)was expressed in a high level an d the recombinan t fusion protein， which was about 41kDa．had immunologicaily reactive activity．This study lay on foundation for th e development of the diagnosis meth ods in serology fo r PRRSV