Disulfide-bridging PEGylation during refolding for the more efficient production of modified proteins.

Proteins that are modified by chemical conjugation require at least two separate purification processes. First the bulk protein is purified, and then after chemical conjugation, a second purification process is required to obtain the modified protein. In an effort to develop new enabling technologies to integrate bioprocessing and protein modification, we describe the use of disulfide-bridging conjugation to conduct PEGylation during protein refolding. Preliminary experiments using a PEG-mono-sulfone reagent with partially unfolded leptin and unfolded RNAse T1 indicated that the cysteine thiols underwent disulfide-bridging conjugation to give the PEGylated proteins. Interferon-ß1b (IFN-ß1b) was then expressed in E.coli as inclusion bodies and found to undergo disulfide bridging-conjugation during refolding. The PEG-IFN-ß1b was isolated by ion-exchange chromatography and displayed in vitro biological activity. In the absence of the PEGylation reagent, IFN-ß1b refolding was less efficient and yielded protein aggregates. No PEGylation was observed if the cysteines on IFN-ß1b were first modified with iodoacetamide prior to refolding. Our results demonstrate that the simultaneous refolding and disulfide bridging PEGylation of proteins could be a useful strategy in the development of affordable modified protein therapeutics.

An Albumin-Free Formulation for Escherichia coli-Derived Interferon Beta-1b with Decreased Immunogenicity in Immune Tolerant Mice.

Human serum albumin (HSA)-free formulation of Escherichia coli-derived human interferon beta (IFNß-1b) with a high percentage of monomeric protein and low immunogenicity is developed and characterized in the current study. UV spectroscopy, fluorescence spectroscopy, dynamic light scattering, sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blotting, Micro-Flow Imaging, resonant mass measurement, size exclusion, and reversed-phase high performance liquid chromatographies were applied to assess the effect of excipients on the stability of IFNß-1b to establish a HSA-free formulation. The antiviral activity of IFNß-1b was evaluated using human lung carcinoma cell line. Immune tolerant mice to hIFNß were used to assess the immunogenicity of the HSA-free formulated IFNß-1b in comparison to Betaferon drug product and Avonex drug substance as standards through IgG titering of plasma. HSA-free formulated IFNß-1b, including 200 mM L-arginine, 200 mM trehalose, and 0.1% n-dodecyl ß-D-maltoside in 10 mM sodium acetate buffer, pH 7.4, showed the highest biological activity. The stability of IFNß-1b in the HSA-free formulation was monitored for 3 weeks at 4°C and 37°C with relative humidity of 10% and 75%, respectively. Protein aggregation and immunogenicity in transgenic mice were decreased in the HSA-free formulated IFNß-1b compared to Betaferon. The stability, biological activity, and immunogenicity of the HSA-free formulation and Betaferon were evaluated. Incubation of formulations at 4°C and 37°C for 3 weeks showed that the HSA-free formulated IFNß-1b was more stable and less immunogenic in transgenic FVB/N mice. Low immunogenicity and the absence of HSA, which reduces the potential risk of viral infection (eg, HIV and HCV), are promising for clinical studies.

[Solubilization Specificities Interferon beta-1b from Inclusion Bodies].

A new solubilization method of recombinant interferon beta-1b (IFNß-1b) from the inclusion bodies was developed. This method allows to extract the target protein selectively in the solutions of different alcohols, such as ethanol, propanol and isopropanol. It was shown that the more effective IFNß-1b solubilization was achieved in the 55% propanol solution. This method allowed to extract the target protein from inclusion bodies around 85-90%, and significantly reduced Escherichia coli content in the solubilizate, in comparison with standard methods.