Sequencing and Com parison of NS2-3 Gene Fragm ent of Classieal Swine Fever Virus Shimen Strain

A couple of CSFV specific primer(PF 5648 and PR 6604)was designed with the aid of computer primer designation software and synthesized based upon the relative conserved regions of published sequenL-~s of C strain．NS2-3 gene(p125 gene)fragment of CSFV Shimen strain was amplified successfu~y by RT-PCR from the anticoagulant blood of infected pig． The product length is 957 bp，located in the central of NS3，a putative NTPase and helicase domain．The ob tained PCR product was cloned and then sequenced．The sequence showed that this fragment con tained all of seven typical consexved segments of helicase superfamily， including two common N11Pbinding motifs，namely，Asite(GXGKT／S)andBsite(3hy，2x)D．Sequence ho mology analysis revealed that Shimen strain had the highest homology wi th Japanese strains(ALD and GPE )，and slightly lower homology with other three CSFV strains (C．Brescia and AI fort)．Shimen strain had also significant homology with two BVDV strains (NADL and SD-1) The deduced amino acid sequence homology of Shimen strain with five CSFV and two BVDV strains was all upper than 90％ ．It is further confirmed that this fragment is the most co nserved in pestivirns amino acid sequence It is cons istent with its essential function in replication and trans lation of virus genome and in processing of polypmtein precursor