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 (rhIFNbeta) 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 rhIFNbeta. Transgenic C57Bl/6 mice that are immune tolerant for human interferon beta (hIFNbeta) have been employed in a mouse model for assessing the breaking of immune tolerance by rhIFNbeta. 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 rhIFNbeta 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 hIFNbeta. Thus, these C57Bl/6 x FVB/N hybrid transgenic mice can be used to study the breaking of immune tolerance for all rhIFNbeta 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 rhIFNbeta-1a variant, PEG-rhIFNbeta-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 rhIFNbeta-1a to break B cell tolerance.