Serial immunoprecipitation assays for interferon--(IFN)-beta antibodies in multiple sclerosis patients

We devised a sensitive, radioimmunoprecipitation assay (RIPA) for anti-interferon (IFN)-beta-binding antibody (BAB) detection. Our RIPA showed good agreement with a reference RIPA (mean difference, -3.2 +/- 10.6 AU), and detected BAB to both IFN-beta-1a and IFN-beta-1b. Neutralizing antibodies to IFN-b (NAB) were also determined with a standard method. BAB and NAB were measured in 393 serum samples from 77 multiple sclerosis (MS) patients treated with IFN-beta-1a or -1b, who were studied over two years, and subsequently classified as responders and non-responders. BAB were found at higher concentrations, and more frequently detected, in IFN-beta-1b- than in IFN-beta-1a-treated patients, and, at highest titres, preferentially in patients who were positive for NAB. However, in our series of MS patients, both titres and frequency of detection of BAB or NAB did not differ between IFN-b responders and non-responders.