Purpose of review: Antibodies against interferon-beta (IFN-beta) can appear in a relevant number of patients. The subset of antibodies that can neutralize IFN-beta activity are called neutralizing antibodies. This review focuses on their impact both on therapeutic efficacy and on bioactivity of IFN-beta, and on the management of antibody-positive patients.
Recent findings: When IFN-betas were first used, neutralizing antibodies were not considered important. However, recent clinical, biologic, and immunologic data have demonstrated that they reduce or abolish the therapeutic efficacy of IFN-beta in 10-20% of patients. Quantification of antibodies using various biologic methods make it difficult to compare among different laboratories, and hence, standardization of assay procedures is necessary. Despite these technical difficulties, data consistently show differences in immunogenicity among the different IFN-beta products and the negative effects of neutralizing antibodies on the clinical efficacy of IFN-betas. Because the therapeutic action of IFN-beta depends on activation of IFN-inducible genes, new methods for the quantification of the biologic activity of IFN-beta have been developed, and a good correlation has been found between the presence of neutralizing antibodies and abrogation of IFN-beta bioactivity.
Summary: Quantification of neutralizing antibodies and the in-vivo bioactivity of IFN-beta through IFN-beta-inducible gene products such as Myxovirus protein A, offer valuable information on IFN-beta therapy. Important questions such as the optimal therapeutic strategy for managing neutralizing antibodies positive patients require further study in clinical trials.