Quantitative detection and typing of HBs Ag and anti-HBs by radioimmunoassay techniques

Small polystyrene tubes coated with purified anti-HBs were used as solid-phase substrate for the detection of HBsAg and anti-HBs by RIA procedures. This substrate yields highly sensitive, reproducible and homogeneous results. The sensitivity and the kinetics of various solid-phase RIA procedures for anti-HBs detection were explored. The preliminary heating of sera at 56 degrees C for 30 min is needed, in order to remove a thermolabile aspecific inhibitor, which is not identifiable with complement. In particular, an RIA procedure is suggested, based upon preincubation of serum to be tested with a serum containing low amounts of HBsAg (count ratio to negative sera = 10:1) and suitable for the combined detection and quantitation of HBsAg and of anti-HBs. The results are expressed as HBs Units, which provide a simple and standardizable unit allowing estimation of HBsAg and anti-HBs amounts over a range of as much as one million values. A number of RIA procedures were also studied for typing HBsAg and anti-HBs, which are also suitable to evaluate 'in vitro' the degree of cross immunity among the various subtypes.