Ultrasensitive Enzymic Radioimmunoasy

This chapter discusses the development and use of ultrasensitive enzymatic radioimmunoassay (USERIA). USERIA combines the advantages of two useful techniques for the measurement of biologically important substances, radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). USERIA is more sensitive than either of the parent assays. ELISA is similar in design to the solid-phase RIA except that an enzyme is used as the immunoglobulin marker instead of a γ-emitting isotope. A competitive USERIA was also performed by antibody competition of B[a]P-DNA attached to the solid phase and B[a]P-DNA in the reaction mixture. For comparison of sensitivity by RIA, ELISA, and USERIA, the standard curves of competitive assays were determined. The comparison of RIA, ELISA, and USERIA for the detection of rotovirus is also discussed in the chapter. It is found that with a reaction time of 1000 min, USERIA is 100-fold more sensitive than ELISA and 1000-fold more sensitive than RIA. It is suggested that, with the activity and specificity of the antiserum employed, constituting the principal limiting factors in the assays, USERIA should prove to be a significant step in the measurement of small amounts of biologically important molecules in body fluid and other solutions.