Point Mutation Approach to Reduce Antigenicity of Interferon Beta

Interferon beta (IFN beta) is naturally occurring cytokine made and secreted by immune cells in response to stimuli. Non-glycosylated interferon beta Ser 17 mutein (IFN beta-Ser17) is widely used for treatment of active relapsing multiple sclerosis. Despite all efforts to humanize this protein, it is still immunogenic by increasing of anti-IFN beta antibodies in patients. In order to decrease its antigenicity, identification and modification of epitopes is an effective step. We used a peptide microarray to detect linear epitopes by screening a synthetic peptide library. The interaction between synthetic peptides and anti-IFN beta antibodies presented in enriched plasma of transgenic and non-transgenic mice, were detected using chemiluminescence. With this technique, three 10-mer peptides were identified as linear epitopes. Computational algorithms were used to select residues suitable for point mutations in each epitope. These three 10-mer epitopes were mutated with the aim to reduce antigenicity of IFN beta. Three variants of IFN beta each with one mutated epitope were produced. The results showed no binding affinity of the mutated epitopes to anti-IFN beta antibodies compared with native epitopes. Biological activities of these epitope variants were measured; equal antiviral activity of the C-terminus mutated and the near N-terminus mutated were evaluated compare to the standard. Our results showed that the antigenicity of IFN beta epitope variants were reduced in vitro.