Hybrid transgenic immune tolerant mouse model for assessing the breaking of B cell tolerance by human interferon beta

Abstract

To date, the therapeutic efficacy of recombinant human proteins is limited by their potential to break B cell tolerance in patients. The formation of neutralising antibodies (NABs) directed against recombinant human interferon beta (rhIFNβ) is associated with a decrease in the therapeutic effect of the protein. For this reason, there is a need to study factors that can cause the immunogenicity of rhIFNβ. Transgenic C57Bl/6 mice that are immune tolerant for human interferon beta (hIFNβ) have been employed in a mouse model for assessing the breaking of immune tolerance by rhIFNβ. In this study, we used the original C57Bl/6 mouse model as well as the hybrid offspring from crossings of transgenic C57Bl/6 mice with wildtype FVB/N mice to study the immunogenicity of three commercial rhIFNβ products, Rebif®, Avonex® and Betaferon®. As determined by ELISA, wildtype C57Bl/6 mice failed to form binding antibodies (BABs) against Rebif® and Avonex® formulated with human serum albumin. Because not all interferon beta products induce antibodies in wildtype C57Bl/6 mice, the transgenic C57Bl/6 mice cannot be used to study the breaking of tolerance by these products. However, the crossing of transgenic C57Bl/6 mice with FVB/N mice resulted in wildtype hybrid offspring in which all products were immunogenic and transgenic hybrid offspring that showed immune tolerance for hIFNβ. Thus, these C57Bl/6 × FVB/N hybrid transgenic mice can be used to study the breaking of immune tolerance for all rhIFNβ products. Of the three products, only Betaferon® was able to break immune tolerance in the transgenic hybrids. With an MxA gene expression inhibition assay, NABs were detected in Betaferon® treated wildtype hybrid mice, but not in transgenic hybrid mice, indicating a distinct immune mechanism in wildtype and transgenic mice. A pegylated rhIFNβ-1a variant, PEG-rhIFNβ-1a, induced antibodies in wildtype hybrid mice, but did not break the immune tolerance of transgenic hybrid mice. This suggests that pegylation did not affect the potential of rhIFNβ-1a to break B cell tolerance.