Assay of Australia Antigen and Antibody Employing Double-Antibody and Solid-Phase Radioimmunoassay Techniques and Comparison with the Passive Hemagglutination Methods

Abstract

Australia antigen (Au) and antibody were assayed by double-antibody (RIA-DA) and solid-phase radioimmunoassay methods and the results were compared with those of other serodiagnostic tests. Purified Au (72 µg protein/ml and approximately 10¹³ particles/ml) was prepared and labeled with ¹²⁵I. The use of a 2-day RIA-DA procedure (anti-Au + unknown, 6 hr; labeled Au, 18 hr; immunoprecipitating antibody, 24 hr) resulted in Au titers that were usually 5- to 35-fold greater than those obtained by the complement fixation (CF) method, and 5- to 10-fold greater than those resulting from the passive hemagglutination (PHA) inhibition procedure. Shortening the RIA-DA procedure to 1 day or using antibody-coated tubes in a solidphase radioimmunoassay system resulted in Au titers that were two- to threefold less than those obtained by the longer RIA-DA method, although both immunoassays were more sensitive than the CF test. RIA-DA and PHA anti-Au titers were comparable.