A Combined Refolding Technique for Recombinant Human Interferon-γ Inclusion Bodies by Ion-exchange Chromatography with a Urea Gradient

Interferon-Based Biopharmaceuticals: Overview on the Production, Purification, and Formulation

The advent of biopharmaceuticals in modern medicine brought enormous benefits to the treatment of numerous human diseases and improved the well-being of many people worldwide. First introduced in the market in the early 1980s, the number of approved biopharmaceutical products has been steadily increasing, with therapeutic proteins, antibodies, and their derivatives accounting for most of the generated revenues. The success of pharmaceutical biotechnology is closely linked with remarkable developments in DNA recombinant technology, which has enabled the production of proteins with high specificity. Among promising biopharmaceuticals are interferons, first described by Isaacs and Lindenmann in 1957 and approved for clinical use in humans nearly thirty years later. Interferons are secreted autocrine and paracrine proteins, which by regulating several biochemical pathways have a spectrum of clinical effectiveness against viral infections, malignant diseases, and multiple sclerosis. Given their relevance and sustained market share, this review provides an overview on the evolution of interferon manufacture, comprising their production, purification, and formulation stages. Remarkable developments achieved in the last decades are herein discussed in three main sections: (i) an upstream stage, including genetically engineered genes, vectors, and hosts, and optimization of culture conditions (culture media, induction temperature, type and concentration of inducer, induction regimens, and scale); (ii) a downstream stage, focusing on single- and multiple-step chromatography, and emerging alternatives (e.g., aqueous two-phase systems); and (iii) formulation and delivery, providing an overview of improved bioactivities and extended half-lives and targeted delivery to the site of action. This review ends with an outlook and foreseeable prospects for underdeveloped aspects of biopharma research involving human interferons.

Apolipoprotein A-I(Milano) anion exchange chromatography: Self association and adsorption equilibrium

The self-associative properties of apolipoprotein A-I(Milano) (apoA-I(M)) were investigated in relationship to its anion exchange behavior on Q-Sepharose-HP with and without the addition of urea as a denaturant. Self-association was dependent on protein and urea concentration and both influenced interactions of the protein with the chromatographic surface. In the absence of urea, apoA-I(M) was highly associated and existed primarily as a mixture of homodimer, tetramer and hexamer forms. Under these conditions, since the binding strength was greater for the oligomer forms, broad, asymmetrical peaks were obtained in both isocratic and gradient elution. Adding urea depressed self-association and caused unfolding. This resulted in sharper peaks but also decreased the binding strength. Thus, under these conditions chromatographic elution occurred at lower salt concentrations. The adsorption isotherms obtained at high protein loadings were also influenced by self-association and by the varying binding strength of the differently associated and unfolded forms. The isotherms were thus dependent on protein, urea, and salt concentration. Maximum binding capacity was obtained in the absence of urea, where adsorption of oligomers was shown to be dominant. Adding urea reduced the apparent binding capacity and weakened the apparent binding strength. A steric mass action model accounting for competitive binding of the multiple associated forms was used to successfully describe the equilibrium binding behavior using parameters determined from isocratic elution and isotherm experiments.

Effects of urea induced protein conformational changes on ion exchange chromatographic behavior

Urea is widely employed to facilitate protein separations in ion exchange chromatography at various scales. In this work, five model proteins were used to examine the chromatographic effects of protein conformational changes induced by urea in ion exchange chromatography. Linear gradient experiments were carried out at various urea concentrations and the protein secondary and tertiary structures were evaluated by far UV CD and fluorescence measurements, respectively. The results indicated that chromatographic retention times were well correlated with structural changes and that they were more sensitive to tertiary structural change. Steric Mass Action (SMA) isotherm parameters were also examined and the results indicated that urea induced protein conformational changes could affect both the characteristic charge and equilibrium constants in these systems. Dynamic light scattering analysis of changes in protein size due to urea-induced unfolding indicated that the size of the protein was not correlated with SMA parameter changes. These results indicate that while urea-induced structural changes can have a marked effect on protein chromatographic behavior in IEX, this behavior can be quite complicated and protein specific. These differences in protein behavior may provide insight into how these partially unfolded proteins are interacting with the resin material.

Oscillatory molecular driving force for protein folding at high concentration: a molecular simulation

This paper presents a Langevin dynamics simulation that suggests a novel way to fold protein at high concentration, a fundamental issue in neurodegenerative diseases in vivo and the production of recombinant proteins in vitro. The simulation indicates that the folding of a coarse-grained beta-barrel protein at high concentration follows the "collapse-rearrangement" mechanism but it yields products of various forms, including single proteins in the native, misfolded, and uncollapsed forms and protein aggregates. Misfolded and uncollapased proteins are the "nucleus" of the aggregates that also encapsulate some correctly folded proteins (native proteins). An optimum hydrophobic interaction strength (epsilon*(p)) between the hydrophobic beads of the model protein, which results from a compromise between the kinetics of collapse and rearrangement, is identified for use in increasing the rate of folding over aggregating. Increased protein concentration hinders the structural transitions in both collapse and rearrangement and thus favors aggregation. A new method for protein folding at high concentration is proposed, which uses an oscillatory molecular driving force (epsilon*(p)) to promote the dissociation of aggregates in the low epsilon*(p) regime while promoting folding at a high epsilon*(p). The advantage of this method in enhancing protein folding while depressing aggregation is illustrated by a comparison with the methods based on direct dilution or applying a denaturant gradient.

On-column refolding of recombinant human interferon-gamma inclusion bodies by expanded bed adsorption chromatography

A refolding strategy was described for on-column refolding of recombinant human interferon-gamma (rhIFN-gamma) inclusion bodies by expanded bed adsorption (EBA) chromatography. After the denatured rhIFN-gamma protein bound onto the cation exchanger of STREAMLINE SP, the refolding process was performed in expanded bed by gradually decreasing the concentration of urea in the buffer and the refolded rhIFN-gamma protein was recovered by the elution in packed bed mode. It was demonstrated that the denatured rhIFN-gamma protein could be efficiently refolded by this method with high yield. Under appropriate experimental conditions, the protein yield and specific activity of rhIFN-gamma was up to 52.7% and 8.18 x 10(6) IU/mg, respectively.