Anti-Interferon-beta Neutralizing Antibody Testing (NAbs)
Neutralizing Antibodies to Interferon-beta in Multiple Sclerosis
Interferon-beta is the first immunomodulatory drug shown to change the natural history of multiple sclerosis. Several recombinant preparations are currently available. A proportion of patients receiving interferon-beta develop drug-induced antibodies. Binding antibodies are measured by binding assays. Such antibodies bind to the drug but may not block the biological activity of the drug. Neutralizing antibodies (NAbs), on the other hand, bind to the drug and block the biological activity of the drug and high levels of antibodies reduce drug efficiency. Several methods have been used to measure NAbs to IFN-beta.
Anti-IFN-beta NAb Testing at the Neuro-Immunology Laboratory
We have been routinely measuring NAbs since July 2007. From July 2007 to February 2011, 1409 samples from 1053 patients have been received from Canada and assayed at the UBC Neuro-Immunology Labs.
We use a Reporter Gene Assay which was developed and validated in 20071. The method uses a cell line which has been transfected with the IFI-161 promoter linked to a luciferase reporter. Patient sera are initially screened for NAb positivity using IFNb-1a, and positive samples are further tested to determine NAb Titre using homologous antigen (interferon which the patient has received).
Antibody results are reported in Tenfold Reduction Units (TRU)/ml as recommended by the World Health Organization. Antibody titres below 20TRU/ml are considered negative and antibody levels above 20TRU/ml are categorized into 3 tiers: low, medium or high titres depending on their rank amongst other samples from patients receiving the same interferon (i.e. a group injected and assayed on beta-1a and a group injected and assayed on beta-1b.)
Positive NAb titres (reported in TRU/ml) from all samples received from July 2007 to February 2011 were ranked by order of increasing titers and stratified into three equal tiers independently for each IFN to construct a NAb reporting reference range.
Requisitions (PDF Files):
IFN-beta Neutralizing Antibodies Requisition (BC Only)
Neuro-Immunology Lab Requisition (CANADA except BC)
Neuro-Immunology Lab Requisition (USA)
1Lam R, Farrell R, Aziz T, Gibbs E, Giovannoni G, Grossberg S, Oger J. Validating parameters of a luciferase reporter gene assay to measure neutralizing antibodies to IFNbeta in multiple sclerosis patients. J Immunol Methods. 2008 Jul 31;336(2):113-8.