The pCVP21 was contructed by inserting the amplified VP2 gene fragment into expression vector pCYTEXP1, containing bacteriophage promoters P R and P L in tandem preceded by the cIts 857 repressor gene.

• 扩增产物经双酶切后插入含噬菌体P?RP?L双强启动子的pCYTEXP1表达质粒，构建了VP2基因克隆pCVP21，经Dot?ELISA筛选出4个VP2表达阳性克隆。