Serum IFN neutralizing antibodies and neopterin levels in a cross-section of MS patients

Objective: To determine levels of serum interferon beta (IFN beta) neutrali zing antibody (NAb) and neopterin-an IFN biologic response marker-in patien ts with MS treated with Betaseron or Avonex. Background: Controversy exists over the relative immunogenicity of IFN beta -1a and IFN beta -1b and the reasons for any such difference. To determine the role of patient profile a nd test methodology in IFN beta, NAb levels need to be measured blindly and simultaneously in a predefined closely matched MS patient cohort. Methods: Serum NAb and neopterin levels were measured in closely matched patients o n Avonex (n = 98) or Betaseron (n = 64). NAb were determined by Athena Diag nostics and serum neopterin levels by Covance Laboratories using a competit ive binding radioimmunoassay. Results: More patients taking Betaseron (22%) than Avonex (7%) had elevated titers of NAb (p = 0.008). Mean serum neopte rin levels were lower in patients with high as compared to low NAb titers ( p = 0.0002). No difference in mean neopterin levels was found comparing the total Betaseron group to the Avonex group; however, in the subset of patie nts with low NAb titers, mean neopterin levels were higher in the Betaseron than in the Avonex group (p = 0.027). A random cross-sectional sampling of patients on Avonex showed a decrease in neopterin levels over time between weekly doses. Conclusion: NAb are more commonly found with Betaseron than Avonex. More studies are needed to determine the correlation among serum ne opterin levels, other biologic response markers, NAb, and disease activity in patients with MS being treated with IFN beta.