Minimal antigenicity of intron A in human recipients demonstrated by three analytical methods

Antibodies to recombinant human interferon alpha 2b (Intron A) were detected in only a small number of 101 Intron A recipients. This group of cancer patients received Intron A for a mean treatment time of 4.3 months and were selected from disease categories in which subjects were expected to be immunocompetent. Three methods for the detection of antibodies were employed: (a) a bioassay measuring the neutralizing activity of the sera for the antiviral action of interferon alpha 2b, (b) a radioimmunological assay measuring the ability of the sera to prevent the detection of interferon alpha 2b by an immunoradiometric assay (IRMA), and (c) an enzyme-linked immunosorbent assay (ELISA) that measures the binding of immunoglobulins to interferon alpha 2b attached to a solid support. Three of the 101 patients developed neutralizing activity during treatment. Two of these exhibited low neutralizing titers of 1:6-1:9 and were unreactive in the IRMA and ELISA, while only one was positive by bioassay, IRMA, and ELISA. An additional seven patients were positive only in the ELISA. Six of these were borderline positive, i.e., the posttreatment:pretreatment ratio was less than or equal to 5. The results of this study confirm that Intron A is minimally antigenic in human subjects.