Application of the paired label radioantibody technique to detection and subtyping of hepatitis B surface antigen.

A sensitive radioimmunoassay has been developed for the detection and subtyping, in regard to w and r specificities, of hepatitis B surface antigens (HBsAg). The binding of monospecific rabbit antibodies directed to either w or r determinant, labeled with 131I and 125I, respectively, by HBsAg was determined in the same experiment, taking advantage of the fact that these specificities are in general, expressed mutually exclusively. HBsAg in the test sample were bound to solid phase guinea pig anti-HBsAg antibody tube before the test. The ratio of percentage uptake of 125I anti-r to that of 131I anti-w for 28 normal sera without antigen was 0.69 0.18. The ratio for seven sera containing HBsAg with w determinant was less than 0.1, and that for 34 with r determinant was more than 10; 100-fold difference was noted between values of w and r antigens.