Objective: To determine if neutralizing antibodies (NAbs) against interferon beta from patients with multiple sclerosis (MS) cross-react with other type 1 interferons, especially endogenous interferon beta, and thus might impede the immune systems of affected patients.
Design: Masked serum samples from MS patients were challenged in vitro against recombinant interferon beta-1a and interferon beta-1b, as well as human leukocyte interferon and fibroblast interferon, the latter representing endogenous interferon. The neutralizing capacity of serum samples on these type 1 interferons was assessed using a luciferase reporter gene assay. Randomly selected samples were titrated to further delineate the cross-reactivity of antibodies.
Setting: University medical center in Düsseldorf, Germany.
Patients: We randomly selected 150 samples from interferon beta-treated MS patients who had previously been tested for the presence of binding antibodies and NAbs.
Main outcome measures: Neutralization of interferon beta bioactivity and cross-reactivity of anti-interferon beta antibodies.
Results: Antibody-mediated neutralization of interferon beta bioactivity in vitro against recombinant interferon beta was observed in all serum samples that had previously tested positive for binding antibodies and NAbs. A neutralizing pattern comparable to that of recombinant interferon beta was observed when endogenous interferon was assessed, reflecting cross-reactivity of NAbs. No differences in neutralization between recombinant and endogenous interferon were observed with respect to the interferon beta preparation used for treatment. Furthermore, no neutralization of other type 1interferons by NAbs could be detected.
Conclusions: A proportion of MS patients who are treated with recombinant interferon beta develop NAbs that also neutralize endogenous interferon. Because NAbs at high titers can persist for years, these antibodies may impede the immune system in affected MS patients regardless of their current treatment regimen.