title: Neutralizing antibodies against interferon β: fluctuation is modest and titre dependent.
abstract: OBJECTIVE
  Neutralizing antibody (NAb) titres may vary over time and thereby some patients can either lose or regain therapeutic effect of interferon beta (IFNbeta). We assessed NAb titres in a large sample of multiple sclerosis (MS) patients to identify the pattern of fluctuation during 1-3 years.
  
  
  METHODS
  Data from IFNbeta-treated MS patients who had been tested for NAbs twice (n = 822) were analysed. NAb titres were compared between the first and the second samples across the critical NAb level of 150 TRU/ml, which we have previously reported to correlate with loss of bioactivity.
  
  
  RESULTS
  Of patients with NAb titres high enough to indicate loss of bioactivity (>150 TRU/ml) in the first analysis 15% showed titres low enough to indicate a regained bioactivity. Conversely, 6% of those without detectable NAbs or NAb titres below the critical level of 150 TRU/ml had shifted to titres above this limit, indicating potential loss of bioactivity. Fluctuation did not differ between IFNbeta preparation used, treatment duration or sampling interval.
  
  
  CONCLUSIONS
  A first NAb test is prognostic for the NAb status during the coming 1-3 years. Choice of IFNbeta preparation had no influence on the chance of reverting to lower levels once NAb titres are high.
authors: Karolinska Institutet, Department of Clinical Neuroscience, Division of Neurology R54, Karolinska University Hospital Huddinge, Stockholm, Sweden.
authors: A
authors: A
authors: Sominanda
authors: J
authors: J
authors: Hillert
authors: A
authors: A
authors: Fogdell-Hahn
mesh_terms: D000328:Adult; D057134:Antibodies, Neutralizing / Q000096:biosynthesis* / Q000097:blood / Q000627:therapeutic use; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods / Q000592:standards; D007165:Immunosuppression Therapy / Q000379:methods; D016899:Interferon-beta / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000276:immunology* / Q000628:therapy*; D011237:Predictive Value of Tests; D011379:Prognosis; D013997:Time Factors
chemical_list: D057134:Antibodies, Neutralizing; D016899:Interferon-beta