A novel assay to detect low-titred antibodies to interferon beta in multiple sclerosis patients

Neutralizing antibodies (NAbs) may compromise interferon (IFN) clinical efficacy in patients with multiple sclerosis (MS) receiving IFN-beta treatment. When bioassays are used for anti-IFN-beta antibody detection, they are unable to discriminate between NAbs or other interfering substances with anti-IFN activity. Here we report the development of an anti-IFN-beta Western blot method that facilitates the detection of IFN low-titred antibodies and characterizes such low neutralizing activity as specifically due to the presence of particular IFN antibodies. The assay was characterized using serum samples from patients with MS treated with IFN-beta. It was developed by adding anti-IFN-positive antibody sera to Dynabeads M-280 tosylactivated followed by Western blot analysis. All sera samples from MS patients with IFN-betala NAbs (< or = 50 t1/10) proved to be antibody-positive using this new method and, more importantly, four of 27 binding antibody-negative sera samples were scored as IFN antibody-positive. The method was found to be rapid, specific and sensitive and consistent with respect to well-established antiviral neutralization or commercial enzyme-linked immunosorbent assays.