Immuno disc assay for screening duck hepatitis B surface antigen in serum, liver tissue and cultured hepatocytes

An immuno disc assay (IDA) for semi-quantitative analysis of the surface antigen (DHBsAg) of duck hepatitis B virus (DHBV) is described. Unpurified antigen preparations were adsorbed onto punched-out nitrocellulose membrane discs. Rabbit antiserum raised against serum-derived gradient-purified DHBsAg was used for detecting the antigen. Cross-reacting antibodies in the rabbit antiserum were removed using normal duck serum and normal duck hepatocytes. The sensitivity of the IDA was compared with that of the Western blot analysis and was observed to be of the same order, but differed slightly for DHBsAg in liver and sera. In contrast to Western blot analysis, antigen specificity for the IDA included the S-protein. Immunodetection was carried out in microtitre plates, but the procedure was accelerated by attaching the antigen-adsorbed discs to an adhesive plate sealer. The IDA was exemplified for measuring DHBsAg in duck serum, duck liver homogenates and viral protein synthesis in cultures of DHBV-infected hepatocytes.