Expression and purification of recombinant human granulocyte colony-stimulating factor in fed-batch culture of Escherichia coli

Production of recombinant scorpion antivenoms in E. coli: current state and perspectives

Scorpion envenomation is a serious health problem in tropical and subtropical zones. The access to scorpion antivenom is sometimes limited in availability and specificity. The classical production process is cumbersome, from the hyper-immunization of the horses to the IgG digestion and purification of the F(ab)'₂ antibody fragments. The production of recombinant antibody fragments in Escherichia coli is a popular trend due to the ability of this microbial host to produce correctly folded proteins. Small recombinant antibody fragments, such as single-chain variable fragments (scFv) and nanobodies (V_HH), have been constructed to recognize and neutralize the neurotoxins responsible for the envenomation symptoms in humans. They are the focus of interest of the most recent studies and are proposed as potentially new generation of pharmaceuticals for their use in immunotherapy against scorpion stings of the Buthidae family. This literature review comprises the current status on the scorpion antivenom market and the analyses of cross-reactivity of commercial scorpion anti-serum against non-specific scorpion venoms. Recent studies on the production of new recombinant scFv and nanobodies will be presented, with a focus on the Androctonus and Centruroides scorpion species. Protein engineering-based technology could be the key to obtaining the next generation of therapeutics capable of neutralizing and cross-reacting against several types of scorpion venoms. KEY POINTS: • Commercial antivenoms consist of predominantly purified equine F(ab)'₂fragments. • Nanobody-based antivenom can neutralize Androctonus venoms and have a low immunogenicity. • Affinity maturation and directed evolution are used to obtain potent scFv families against Centruroides scorpions.

Inclusion Bodies: Status Quo and Perspectives

Multiple E. coli cultivations, producing recombinant proteins, lead to the formation of inclusion bodies (IBs). IBs historically were considered as nondesired by-products, due to their time- and cost-intensive purification. Nowadays, many obstacles in IB processing can be overcome. As a consequence, several industrial processes with E. coli favor IB formation over soluble production options due to the high space time yields obtained. Within this chapter, we discuss the state-of-the art biopharmaceutical IB process, review its challenges, highlight the recent developments and perspectives, and also propose alternative solutions, compared to the state-of-the art processing.

Optimizing Granulocyte Colony-Stimulating Factor Transcript for Enhanced Expression in Escherichia coli

The human granulocyte colony-stimulating factor (G-CSF) is a hematopoietic growth factor used to prevent and treat neutropenia. G-CSF stimulates the bone marrow to produce infection-fighting granulocytes. Food and Drug Administration of the United States approved G-CSF in 1991 and its PEGylated version in 2002 as a prophylactic and therapeutic measure against neutropenia. Recombinant human G-CSF is produced in surrogate host Escherichia coli and is PEGylated at N-terminal. Besides neutropenia, G-CSF is also used in bone marrow transplantation for the mobilization and maturation of peripheral blood stem cells. Considering the requirement of producing G-CSF therapeutic in large quantities, construct designing for high expression is critical for the biopharmaceutical and industrial application. Earlier studies have employed approaches such as codon optimization, use of strong promoters, employment of protein tags, secretion signals, optimization of protein folding, etc., for increasing expression and yield of therapeutic proteins. In this study, it was observed that mRNA transcribed from the native human cDNA of G-CSF and the codon-optimized variant leads to low protein expression in E. coli. To understand the underlying reasons, the mRNA secondary structure of the 5′ end of the G-CSF transcript was analyzed. This analysis revealed the presence of stable secondary structures at the 5′ end of the G-CSF transcript, arising from the native human gene and even from the codon-optimized sequence. These secondary structures were disrupted through translationally silent mutations within the first 24 nucleotides of the transcript without affecting the protein sequence. Interestingly, through this approach, the G-CSF protein expression was increased 60 folds as compared to native G-CSF construct. We believe that these findings create a roadmap for optimization of G-CSF transcript for enhanced expression in E. coli and could be employed to increase the expression of other therapeutic proteins.

Development of recombinant human granulocyte colony-stimulating factor (nartograstim) production process in Escherichia coli compatible with industrial scale and with no antibiotics in the culture medium

The granulocyte colony-stimulating factor (G-CSF) is a hematopoietic cytokine that has important clinical applications for treating neutropenia. Nartograstim is a recombinant variant of human G-CSF. Nartograstim has been produced in Escherichia coli as inclusion bodies (IB) and presents higher stability and biological activity than the wild type of human G-CSF because of its mutations. We developed a production process of nartograstim in a 10-L bioreactor using auto-induction or chemically defined medium. After cell lysis, centrifugation, IB washing, and IB solubilization, the following three refolding methods were evaluated: diafiltration, dialysis, and direct dilution in two refolding buffers. Western blot and SDS-PAGE confirmed the identity of 18.8-kDa bands as nartograstim in both cultures. The auto-induction medium produced 1.17 g/L and chemically defined medium produced 0.95 g/L. The dilution method yielded the highest percentage of refolding (99%). After refolding, many contaminant proteins precipitated during pH adjustment to 5.2, increasing purity from 50 to 78%. After applying the supernatant to cation exchange chromatography (CEC), nartograstim recovery was low and the purity was 87%. However, when the refolding solution was applied to anion exchange chromatography followed by CEC, 91%-98% purity and 2.2% recovery were obtained. The purification process described in this work can be used to obtain nartograstim with high purity, structural integrity, and the expected biological activity. KEY POINTS: • Few papers report the final recovery of the purification process from inclusion bodies. • The process developed led to high purity and reasonable recovery compared to literature. • Nartograstim biological activity was demonstrated in mice using a neutropenia model.

High-level expression of a novel liver-targeting fusion interferon with preferred Escherichia coli codon preference and its anti-hepatitis B virus activity in vivo

Background

In our previous study, a novel liver-targeting fusion interferon (IFN-CSP) combining IFN α2b with plasmodium region I peptide was successfully constructed. IFN-CSP has significant inhibition effects on HBV-DNA replication in HepG2.2.15 cells. The aim of the present investigation was focused on how to produce high levels of recombinant IFN-CSP and its in vivo anti-hepatitis B virus (HBV) activity.

Methods

A modified DNA fragment encoding IFN-CSP was synthesized according to Escherichia coli (E. coli) preferred codon usage and transformed into E. coli BL21 (DE3) for protein expression. The induction conditions were systematically examined by combining one-factor experiments with an orthogonal test (L(9)(3)(4)). The antigenicity of the purified protein was characterized by western blot analysis. The in vivo tissue distribution were assayed and compared with native IFN α2b. HBV-transgenic mice were used as in vivo model to evaluate the anti-HBV effect of the recombinant IFN-CSP.

Results

The results showed that the E. coli expression system was very efficient to produce target protein.

Conclusion

Our current research demonstrates for the first time that IFN-CSP gene can be expressed at high levels in E. coli through codon and expression conditions optimization. The purified recombinant IFN-CSP showed liver-targeting potentiality and anti-HBV activity in vivo. The present study further supported the application of IFN-CSP in liver-targeting anti-HBV medicines.

Influence of pH control in the formation of inclusion bodies during production of recombinant sphingomyelinase-D in Escherichia coli

BACKGROUND

Inclusion bodies (IBs) are aggregated proteins that form clusters when protein is overexpressed in heterologous expression systems. IBs have been considered as non-usable proteins, but recently they are being used as functional materials, catalytic particles, drug delivery agents, immunogenic structures, and as a raw material in recombinant therapeutic protein purification. However, few studies have been made to understand how culture conditions affect the protein aggregation and the physicochemical characteristics that lead them to cluster. The objective of our research was to understand how pH affects the physicochemical properties of IBs formed by the recombinant sphingomyelinase-D of tick expressed in E. coli BL21-Gold (DE3) by evaluating two pH culture strategies.

RESULTS

Uncontrolled pH culture conditions favored recombinant sphingomyelinase-D aggregation and IB formation. The IBs of sphingomyelinase-D produced under controlled pH at 7.5 and after 24 h were smaller (<500 nm) than those produced under uncontrolled pH conditions (>500 nm). Furthermore, the composition, conformation and β-structure formation of the aggregates were different. Under controlled pH conditions in comparison to uncontrolled conditions, the produced IBs presented higher resistance to denaturants and proteinase-K degradation, presented β-structure, but apparently as time passes the IBs become compacted and less sensitive to amyloid dye binding.

CONCLUSIONS

The manipulation of the pH has an impact on IB formation and their physicochemical characteristics. Particularly, uncontrolled pH conditions favored the protein aggregation and sphingomyelinase-D IB formation. The evidence may lead to find methodologies for bioprocesses to obtain biomaterials with particular characteristics, extending the application possibilities of the inclusion bodies.