What are interferon-beta neutralizing antibodies and do they matter?
Neutralizing antibodies (NAB) to interferon-beta occur in some patients receiving human recombinant inteferon-beta. NAB are detected in patients by demonstrating that a serum sample can block in vitro a biologic effect of interferon-beta, such as inhibition of viral infection or induction of MX protein. NAB bind to interferon-beta and interfer with its ability to bind to the Type I inferferon receptor. There are commercially available tests to detect NAB. NAB are given a titer and typically titers > 20 are considered significant. The three formulations of interferon-beta differ in the prevalence of induction of NAB. Avonex induces significant NAB titers in 2-5% of patients; Rebif induces NAB in 15-25% of patients; Betaseron induces NAB in ~30% of patients. NAB typically appear 6-18 months after therapy is started. They may disappear after continued therapy but frequently do not, particularly if the titer is >100. NAB induced by one interferon-beta product cross react with the other pro
