Simultaneous use of poly- and monoclonal antibodies as enzyme tracers in a one-step enzyme immunoassay for the detection of hepatitis B surface antigen.

A one-step third generation enzyme immunoassay (EIA) was developed for the detection of hepatitis B surface antigen (HBsAg) in human serum or plasma using a polyclonal (Pab-HBsAg) and two monoclonal antibodies to HBsAg (Mab1-HBsAg and Mab2-HBsAg). In this assay, the solid phase is coated with Mab1-HBsAg and the specimen is incubated simultaneously with peroxidase labelled Pab-HBsAg and Mab2-HBsAg. If HBsAg is present in a specimen it will form sandwich complexes with capture and tracer antibodies. The hook effect, observed in some HBsAg detection tests when a high concentration of HBsAg is present, was minimized in this assay by increasing the concentration of the peroxidase-labelled Mab2-HBsAg. The sensitivity of this assay for HBsAg/ay and HBsAg/ad subtypes in a standard (2 h incubation) procedure was 0.6 and 0.3 ng/ml and in an overnight (16-22 h incubation) procedure 0.2 and 0.15 ng/ml, respectively. Strong elimination of the hook effect was observed with specimens containing high levels of HBsAg compared with test results using peroxidase-labelled Pab-HBsAg alone as enzyme tracer. This EIA offers a procedure, with a high specificity and wide range of sensitivity for the detection of HBsAg in human sera or plasma.