A comparative study on two radioimmunoassays with cloned human interferon-alpha.

We report here on the development of (a) a double-antibody radioimmunoassay and (b) a solid-phase radioimmunoassay for cloned human interferon-alpha (leukocyte) [HuIFN-alpha(Le)]. We present the results of titrations of human interferon-alpha-2 (HuIFN-alpha 2) using either method under experimental and optimized conditions. A comparative study of the two methods indicates that (a) the double-antibody procedure is 200-fold more economical of antibody when quantitations are carried out within an optimal range of 0.05--1.0 ng; (b) the double-antibody method is fivefold more sensitive than the solid-phase method, its sensitivity being within the range of the antiviral assays for interferons; and (c) the solid-phase assay is significantly faster. The data also support the presence in human serum of a factor(s) that decreases the maximal amount of HuIFN-alpha 2 bound to antibody. We conclude that these radioimmunoassays are superior to biological assays for the quantitation of interferon-alpha polypeptides from the standpoints of objectivity and reproducibility as well as time and effort required.