To establish a highly specific,sensitive,and efficient method for detecting antibodies a-gainst the Erns protein of classical swine fever virus(CSFV),and to distinguish CSFV vaccine strains from wild strains infections in combination with the E2 subunit vaccine.The purified Erns protein of the CSFV expressed by baculovirus was conjugated to carboxylated magnetic beads as a solid-phase carrier and horseradish peroxidase(HRP),separately.A double-antigen sandwich chemiluminescent enzyme immunoassay(CLEIA)was developed by optimizing various reaction parameters using a fully automated chemiluminescence analyzer.This method was then applied to quantitatively detect Erns protein antibodies in sera from pigs infected with prevalent strains and those immunized with the CSFV E2 subunit vaccine and challenged with field strains.The results showed that the optimal conditions for coupling protein-to-magnetic bead were as follows:coupling buffer pH of 8.0,a protein coupling amount of 2.5 mg/g,blocking solution of 10％BSA,serum sample volume of 20 μL.The optimal dilution of enzyme-labeled antigen was at 1:500 with a one-step reaction time of 15 minutes.The cutoff value of the established CLEIA method for detecting CSFV Erns protein antibodies was 5.83 U/mL and a diagnostic sensitivity of 1:128.No cross-reac-tivity was observed with positive sera against African swine fever virus,pseudorabies virus,porcine circovirus type 2,porcine epidemic diarrhea virus,porcine reproductive and respiratory syndrome virus,or porcine gastroenteritis virus.Additionally,the method yielded negative results with sera from pigs immunized with the E2 subunit vaccine.In repeatability tests,the intra-assay coefficient of variation(CV)ranged from 0.77％to 11.56％,and the inter-assay CV ranged from 10.30％to 14.55％,both below 15％.The positive and negative concordance rates with a commercial CSFV Erns protein antibody detection kit were 95.24％and 92.71％,separately,with an overall concord-ance rate of 93.23％.The double-antigen sandwich chemiluminescence method established in this study exhibits high sensitivity,excellent repeatability,and suitability for automated detection,making it applicable for serological differentiation between CSFV E2 subunit vaccination and infec-tion with prevalent strains.

To establish a highly specific,sensitive,and efficient method for detecting antibodies a-gainst the Erns protein of classical swine fever virus(CSFV),and to distinguish CSFV vaccine strains from wild strains infections in combination with the E2 subunit vaccine.The purified Erns protein of the CSFV expressed by baculovirus was conjugated to carboxylated magnetic beads as a solid-phase carrier and horseradish peroxidase(HRP),separately.A double-antigen sandwich chemiluminescent enzyme immunoassay(CLEIA)was developed by optimizing various reaction parameters using a fully automated chemiluminescence analyzer.This method was then applied to quantitatively detect Erns protein antibodies in sera from pigs infected with prevalent strains and those immunized with the CSFV E2 subunit vaccine and challenged with field strains.The results showed that the optimal conditions for coupling protein-to-magnetic bead were as follows:coupling buffer pH of 8.0,a protein coupling amount of 2.5 mg/g,blocking solution of 10％BSA,serum sample volume of 20 μL.The optimal dilution of enzyme-labeled antigen was at 1:500 with a one-step reaction time of 15 minutes.The cutoff value of the established CLEIA method for detecting CSFV Erns protein antibodies was 5.83 U/mL and a diagnostic sensitivity of 1:128.No cross-reac-tivity was observed with positive sera against African swine fever virus,pseudorabies virus,porcine circovirus type 2,porcine epidemic diarrhea virus,porcine reproductive and respiratory syndrome virus,or porcine gastroenteritis virus.Additionally,the method yielded negative results with sera from pigs immunized with the E2 subunit vaccine.In repeatability tests,the intra-assay coefficient of variation(CV)ranged from 0.77％to 11.56％,and the inter-assay CV ranged from 10.30％to 14.55％,both below 15％.The positive and negative concordance rates with a commercial CSFV Erns protein antibody detection kit were 95.24％and 92.71％,separately,with an overall concord-ance rate of 93.23％.The double-antigen sandwich chemiluminescence method established in this study exhibits high sensitivity,excellent repeatability,and suitability for automated detection,making it applicable for serological differentiation between CSFV E2 subunit vaccination and infec-tion with prevalent strains.

Many methods can by used for the quantitative determination of the three types of immu-noglobulin. On the basis of the single radial immuno-diffusion method used by John L. Fahey,certain modifications have been made on the methods of diluting standard solutions and theirconcentrations, and the standard concentration of the immunoglobulins and the antibody-con-taining agar diffusion plates. In order to find the optimum condition of cultivation, theeffects of various temperatures and various cultivation time given by G. Mancini et al havebeen checked, and satisfactory standard curves have been obtained. Therefore, the accuracyof the analytical results is guaranteed. According to the results obtained, there is no observable effect on the diameter of theprecipitating ring when the temperature in culture-box is 35?C to 40?C and the cultivationtime extends to 96 hrs.

0.05). The non-significant differences may be due to the small number of cases examined.