A radioimmunoassay to determine the subtypes D and Y of the hepatitis-B surface antigen.

A radioimmunologic test system for determining the subtypes D and Y of the hepatitis-B surface antigen (HBs-Ag, Australia antigen, HAA) is described. This technique uses the immunoadsorption principle. The antigen to be subtyped is incubated with an antiserum which contains (125)I-labeled antibodies to the antigenic determinants a, d, and y. The specificity of the antibody which is not consumed in forming the antigen-antibody complex is determined by absorption on agarose to which HBs-Ag of subtypes D and Y is coupled. This specificity permits conclusions as to the subtype of the hepatitis-B surface antigen which is being investigated.