Solid-phase RIA for the detection of subtype-specific hepatitis-B antigen determinants

With sensitive methods like radioimmunoassay (RIA) and enzyme immunoassay (EIA), HBsAg can be detected already at a concentration of 2 ng/ml specific antigen protein. Until now, the HBsAg subtype determinants have usually been detected by migration electrophoresis with a detection limit of 1000 ng/ml and immunodiffusion (1D) with a detection limit of about 3000 ng/ml. As these methods are rather unsensitive, a great part of RIA positive sera could never be typified until now. The paper describes an RIA with labelled subtype-specific antibodies for a specific detection of the antigen determinants d and y even at only 10 ng/ml. In an investigation of 251 sera not typified so far, 11 sera had the subtype determinant y, and 65 sera could still not be typed. The amount of non-typfiable sera is thus reduced from 23.2 to 6.4%. The relative frequency of subtype adw against ayn in RIA-typified sera corresponded to the distribution obtained in the earlier method. In the RIA the adw /ayw ratio was 63:37, in the earlier method 60:40. (orig.)