The major immunogenic proteins (Ems,E2 and NS3) of classical swine fever virus (CSFV) (Shimen strain) were expressed in E.coli and purified by affinity chromatography.The recombinant antigens were applied to develop multiple enzyme-linked immunosorbent assays (ELISAs) for the detection of specific antibodies in pig sera.Optimum cut-off values were determined by receiver operating characteristic (ROC) analysis after testing 201 sera of vaccinated pigs and 64 negative sera of unvaccinated piglets.The multiple ELISAs were validated with 265 pig sera yielding high sensitivity and specificity in comparison with the virus neutralization results.The results demonstrated that multiple ELISAs can be a valuable tool for the detection of CSFV infection and serological surveys in CSFV-free countries or for the evaluation of the antibody responses in pigs induced by a live attenuated C-strain vaccination.

OBJECTIVE:To investigate the inhibitory effect of siRNA expression vector inhibiting human insulin-like growth factor 2(IGF2)gene on the proliferation of hepatoma cell line Huh-7. METHODS:siRNA expression vector pGL3-hAFP-hTERT-siRNA3(“siRNA3”)which inhibited IGF2 gene by dual promoter regulation of recombinant human alpha-foetoprotein(hAFP)and human telomerase reverse transcriptase(hTERT)was transfected into the Huh-7 cell and normal hepatocyte L-02,and then a nega-tive control group(vector pGL3-hAFP-hTERT)and a blank control group were set up. IGF2 mRNA expression was detected by re-al-time fluorescent quantitative polymerase chain reaction 48 h after transfection into the cells in all groups;the activity of the cells by the microplate reader 0,24,48 and 72 h thereafter;and the cell cycle and apoptosis by the flow cytometer 48 h thereafter,and the changes in the protein levels of IGF2,PCNA,Cyclin E2,Cyclin D2,Cdc2 and Bcl-2 in the cell were detected by Western blot. RESULTS:Compared with the negative control group and blank control group,IGF2 mRNA expression in the Huh-7 cell transfected with siRNA3 was obviously weaker;at 48 and 72 h after transfection,the activity of Huh-7 cell signigicantly reduced, Huh-7 cells at G1 phase obviously increased and those at S phase markedly decreased;the occurrence of early,late and total apopto-sis in Huh-7 cells apparently increased,and the protein expression of IGF2,PCNA,Cyclin E2,Cyclin D2,Cdc2 and Bcl-2 in cells significantly weakened,with statistically significance(P<0.01 or P<0.05). No obvious change in the above-mentioned index-es could be found in L-02 cells transfected with siRNA3 expression vector (P>0.05). CONCLUSIONS:siRNA which inhibited IGF2 gene by dual promoter regulation of recombinant hAFP and hTERT can specially inhibit IGF2 gene expression and the prolifer-ation of Huh-7 cells,which may be involved with down-regulated protein expression of cell proliferation-associated gene PCNA, cell cycle control-associated genes Cyclin E2,Cyclin D2 and Cdc2 and apoptosis regulation-associated gene Bcl-2 as a result of down-regulated IGF2 mRNA expression and protein expres-sion.