Abstract: In order to identify the highly virulent strain (Shimen) and vaccine strain (HCLV) of classical swine fever virus (CSFV),a pair of specific primers was designed against conserved domain of envelop glycoprotein E2 gene of CSFV sequence published in GenBank. A specific site of BglⅡ for restriction enzyme digestion was found and placed within PCR primers. The shimen strain and vaccine strain of CSFV were distinguished using single digestion of RT-PCR products with Bgl Ⅱ. Specificity and sensitivity were detected in parallel. A specific 750 bp fragment was amplified from both Shimen strain and vaccine strain of CSF with this method. The RT-PCR products of vaccine strain could not be cut by Bgl Ⅱ,while Shimen strain could be cut into two fragments of 520 and 230 bp length respectively. The conserved E2 gene fragment of CSFV could be amplified specifically with this assay,and the detection limit was 3.96×10^－4 μg/mL of RNA. This assay was also evaluated with 30 clinical samples, 3 of them were detected with Shimen strain of CSF infection,21 of them were vaccine strains,others were CSFV negative.

Key words: classical swine fever virus; highly virulent strain and vaccine strain; RT-PCR; digestion