Abstract: Postweaning multisystemic wasting syndrome of swine (PMWS)is associated with porcine circovirus type 2(PCV2). Simple and reliable diagnostic methods are needed to detect antibodies against PCV2 for monitoring early PCV2 infection.An indirect enzyme linked immunosorbent assay (ELISA) method based on purified recombinant capsid protein (Cap) was established to detect IgM antibodies against PCV2. The purified PCV2 Cap protein was used to coat 96 well plate as the antigen,and the following factors affected the experiments were optimized. The results demonstrated that optimal concentration of Cap protein for coating was 1.25 μg/mL,the optimal dilution of serum sample was 1∶100. The cutoff value was 0.35. The results showed no cross-reactivity with positive serum of other five porcine virus. The CV of intra-assay and interassay ranged from 2% to 6%. The indirect ELISA was used to detect 100 field serum samples, compared with control IgG/IgM kit,the diagnostic sensitivity,specificity,and accuracy of PCV2 IgM were 90.3%,92.8% and 92%. The result showed that the indirect ELISA was not only sensitive and specific,but also suitable for large scale epidemiological investigation of early PCV2 infection.

Key words: porcine circovirus type 2; IgM antibody; capsid protein; indirect ELISA