Recombinant Therapeutic Proteins Research Articles

Purification of inclusion bodies using PEG precipitation under denaturing conditions to produce recombinant therapeutic proteins from Escherichia coli

It has been documented that the purification of inclusion bodies from Escherichia coli by size exclusion chromatography (SEC) may benefit subsequent refolding and recovery of recombinant proteins. However, loading volume and the high cost of the column limits its application in large-scale manufacturing of biopharmaceutical proteins. We report a novel process using polyethylene glycol (PEG) precipitation under denaturing conditions to replace SEC for rapid purification of inclusion bodies containing recombinant therapeutic proteins. Using recombinant human interleukin 15 (rhIL-15) as an example, inclusion bodies of rhIL-15 were solubilized in 7M guanidine hydrochloride, and rhIL-15 was precipitated by the addition of PEG 6000. A final concentration of 5% (w/v) PEG 6000 was found to be optimal to precipitate target proteins and enhance recovery and purity. Compared to the previously reported S-200 size exclusion purification method, PEG precipitation was easier to scale up and achieved the same protein yields and quality of the product. PEG precipitation also reduced manufacturing time by about 50 and 95% of material costs. After refolding and further purification, the rhIL-15 product was highly pure and demonstrated a comparable bioactivity with a rhIL-15 reference standard. Our studies demonstrated that PEG precipitation of inclusion bodies under denaturing conditions holds significant potential as a manufacturing process for biopharmaceuticals from E. coli protein expression systems.

Efficient expression of stable recombinant human insulin-like growth factor-1 fusion with human serum albumin in Chinese hamster ovary cells

ABSTRACTInsulin-like growth factor-1 (IGF-1) plays a crucial role in cell development, differentiation, and metabolism, and has been a potential therapeutic agent for many diseases. Chinese hamster ovary (CHO) cells are widely used for production of recombinant therapeutic proteins, but the expression level of IGF-1 in CHO cells is very low (1,500 µg/L) and the half-life of IGF-1 in blood circulation is only 4.5 min according to previous studies. Therefore, IGF-1 was fused to long-circulating serum protein human serum albumin (HSA) and expressed in CHO cells. After 8-day fed-batch culture, the expression level of HSA–IGF-1 reached 100 mg/L. The fusion protein HSA–IGF-1 was purified with a recovery of 35% using a two-step chromatographic procedure. According to bioactivity assay, the purified HSA–IGF-1 could stimulate the proliferation of NIH3T3 cells in a dose-dependent fashion and promote the cell-cycle progression. Besides this, HSA–IGF-1 could bind to IGF-1 receptor on cell membrane and activate the intracellular PI3K/AKT signaling pathway. Our study suggested that HSA fusion technology carried out in CHO cells not only provided bioactivity in HSA–IGF-1 for further research but also offered a beneficial strategy to produce other similar cytokines in CHO cells.

Hybrid Approach to State Estimation for Bioprocess Control.

An improved state estimation technique for bioprocess control applications is proposed where a hybrid version of the Unscented Kalman Filter (UKF) is employed. The underlying dynamic system model is formulated as a conventional system of ordinary differential equations based on the mass balances of the state variables biomass, substrate, and product, while the observation model, describing the less established relationship between the state variables and the measurement quantities, is formulated in a data driven way. The latter is formulated by means of a support vector regression (SVR) model. The UKF is applied to a recombinant therapeutic protein production process using Escherichia coli bacteria. Additionally, the state vector was extended by the specific biomass growth rate µ in order to allow for the estimation of this key variable which is crucial for the implementation of innovative control algorithms in recombinant therapeutic protein production processes. The state estimates depict a sufficiently low noise level which goes perfectly with different advanced bioprocess control applications.

A novel approach to characterize host cell proteins associated with therapeutic monoclonal antibodies.

Recombinant monoclonal antibody (mAb) products are widely produced in the pharmaceutical industry using Chinese hamster ovary (CHO) cells. Host cell proteins (HCPs) are one of many process-related impurities generated during the production of mAb products. The multi-analyte HCP enzyme linked immunosorbent assay (ELISA) is the industry standard accepted assay to measure clearance of HCPs from recombinant protein therapeutics. While similar platform processes are used for expression and purification, varying amounts of HCPs are found in final drug substances for different mAb products. Through the use of novel ELISA formats, an HCP-mAb product interaction was identified using a variety of ELISAs to investigate the underlying protein-protein interaction. This result provides evidence to explain why some mAb products have HCPs that are not cleared during purification. This ELISA technique can be used as a high-throughput screening tool to identify conditions to improve clearance of difficult HCPs during downstream processing purification. In addition, an interaction was observed to occur between anti-CHO HCP antibodies and mAb products. However, this interaction only occurs under denaturing conditions, and does not interfere with the HCP quantitation obtained by ELISA, and it was demonstrated that the cross-reactive anti-CHO HCP antibodies can be removed by affinity purification. Biotechnol. Bioeng. 2017;114: 1208-1214. © 2017 Wiley Periodicals, Inc.

Recent advances in (therapeutic protein) drug development.

Therapeutic protein drugs are an important class of medicines serving patients most in need of novel therapies. Recently approved recombinant protein therapeutics have been developed to treat a wide variety of clinical indications, including cancers, autoimmunity/inflammation, exposure to infectious agents, and genetic disorders. The latest advances in protein-engineering technologies have allowed drug developers and manufacturers to fine-tune and exploit desirable functional characteristics of proteins of interest while maintaining (and in some cases enhancing) product safety or efficacy or both. In this review, we highlight the emerging trends and approaches in protein drug development by using examples of therapeutic proteins approved by the U.S. Food and Drug Administration over the previous five years (2011–2016, namely January 1, 2011, through August 31, 2016).

Exosomes: Nanoparticulate tools for RNA interference and drug delivery.

Exosomes are naturally occurring extracellular vesicles released by most mammalian cells in all body fluids. Exosomes are known as key mediators in cell‐cell communication and facilitate the transfer of genetic and biochemical information between distant cells. Structurally, exosomes are composed of lipids, proteins, and also several types of RNAs which enable these vesicles to serve as important disease biomarkers. Moreover, exosomes have emerged as novel drug and gene delivery tools owing to their multiple advantages over conventional delivery systems. Recently, increasing attention has been focused on exosomes for the delivery of drugs, including therapeutic recombinant proteins, to various target tissues. Exosomes are also promising vehicles for the delivery of microRNAs and small interfering RNAs, which is usually hampered by rapid degradation of these RNAs, as well as inefficient tissue specificity of currently available delivery strategies. This review highlights the most recent accomplishments and trends in the use of exosomes for the delivery of drugs and therapeutic RNA molecules.

Systemically Administered, Target-Specific Therapeutic Recombinant Proteins and Nanoparticles for Regenerative Medicine

Growth factors, chemokines, and cytokines responsible for tissue regeneration have been identified. Their therapeutic usage in humans is almost nonexistent because of the difficulty in maintaining their bioactivity in the protease-rich milieu of injured tissues. Safety concerns have ruled out the systemic administration of growth factors. Angiogenic vasculature forming in the regenerating tissues has unique molecular structures, so-called "zip/postal codes". These unique vascular zip codes provide an opportunity for target-specific delivery of systemically administered therapeutics to tissue injuries by ligands (using peptides or antibodies as a delivery vehicle) binding to these specific structures. Molecules with therapeutic potential can also be packaged into nanocarriers which then can be targeted to the desired location by placing large number of peptides on the nanoparticle. The targeted delivery of systemically administered recombinant proteins to the injured tissue is hopefully rapidly advanced to provide new therapeutics to regenerative medicine.

Immunogenicity of recombinant analog of antitumor protein lactaptin

Therapeutic monoclonal antibodies and recombinant proteins including cytokines are commonly used in the treatment of cancer and inflammatory diseases. In most cases, these protein-based drugs exhibit a high therapeutic efficacy, which is unfortunately frequently associated with a variety of side effects. We have investigated the in vitro and in vivo immunogenicity of recombinant antitumor protein lactaptin (RL2). Based on the qRT-PCR analysis, we have shown that, in MDA-MB-231 human breast adenocarcinoma cells, RL2 suppresses the NF-kB signaling cascade that regulates the reactions of innate immunity. RL2 inhibits the expression of the CXCL1 protein and apoptosis inhibitor A20 and enhances expression of IkB, NF-kB repressor. The ELISA method has been used to evaluate the antibody titer in the blood of mice, which received single and triple intravenous or intraperitoneal injections of RL2. The multiplex immunoassay of 23 cytokines in the mice blood has shown that the RL2 injections lead to a slight increase in the levels of systemic pro-inflammatory cytokine interleukin-5 (IL-5) and keratinocyte chemoattractant (KC), a homologue of human macrophage inflammatory protein-1 (MIP-1). These observations indicate the low immunogenicity of the recombinant lactaptin analog, which can be considered to be a potential molecular drug candidate for further clinical development.

Continuous Manufacturing of Recombinant Therapeutic Proteins: Upstream and Downstream Technologies.

Continuous biomanufacturing of recombinant therapeutic proteins offers several potential advantages over conventional batch processing, including reduced cost of goods, more flexible and responsive manufacturing facilities, and improved and consistent product quality. Although continuous approaches to various upstream and downstream unit operations have been considered and studied for decades, in recent years interest and application have accelerated. Researchers have achieved increasingly higher levels of process intensification, and have also begun to integrate different continuous unit operations into larger, holistically continuous processes. This review first discusses approaches for continuous cell culture, with a focus on perfusion-enabling cell separation technologies including gravitational, centrifugal, and acoustic settling, as well as filtration-based techniques. We follow with a review of various continuous downstream unit operations, covering categories such as clarification, chromatography, formulation, and viral inactivation and filtration. The review ends by summarizing case studies of integrated and continuous processing as reported in the literature.

Animal Cell Expression Systems.

The glycan profile of therapeutic recombinant proteins such as monoclonal antibodies is a critical quality attribute, which affects the efficacy of the final product. The cellular glycosylation process during protein expression is dependent upon a number of factors such as the availability of substrates in the media, the intracellular content of nucleotide sugars, and the enzyme repertoire of the host cells. In order to control the variability of glycosylation it is important to understand the critical process parameters and their acceptable range of values to enable reproducible production of proteins with a predetermined glycan profile providing the desired biological function or therapeutic effect. The depletion of critical nutrients such as glucose or galactose, which may occur toward the end of a culture process, can lead to truncated glycans. Terminal galactosylation and sialyation are particularly variable but may be controlled by the presence of some key media components. Ammonia accumulation, pH, and dissolved oxygen levels are also known to be key bioprocess parameters that affect the glycosylation of recombinant proteins. Specific enzyme inhibitors can be added to the media to drive the formation of selected and predetermined glycan profiles. Various attempts have been made to predict the glycan profiles of cellular expressed proteins and have led to metabolic models based upon knowledge of metabolic flux and the kinetics of individual glycosylation reactions.In contrast to single recombinant proteins, the glycan profiles of viral vaccines are far more complex and difficult to predict. The example of influenzaA virus shows that hemagglutinin, the major antigenic determinant, has three to nine N-glycans, which may influence the antigenicity and efficacy of the vaccine. Glycosylation of the influenzaA virus has been largely unmonitored in the past as production has been from eggs, where glycan profiles of antigens are difficult if not impossible to control. Over the past decade, however, there have been various commercial influenza vaccines made available from cell technology using animal host cells. Analysis of glycosylation control shows that the type of host cell has the greatest influence on the final analyzed glycan profile. Other factors such as the virus strain, the cultivation system, or various process parameters have been shown to have only a minor effect on the glycosylation pattern. We predict that the analysis of glycan profiles in viral vaccines will become increasingly important in the development and consistent manufacturing of safe and potent vaccines. Graphical Abstract.

Enabler for process analytical technology implementation in Pichia pastoris fermentation: Fluorescence-based soft sensors for rapid quantitation of product titer.

Rapid quantitation of product titer is a critical input for control of any bioprocess. This measurement, however, is marred by the myriad components that are present in the fermentation broth, often requiring extensive sample pretreatment before analysis. Spectroscopy techniques such as fluorescence spectroscopy are widely recognized as potential monitoring tools. Here, we investigate the possibility of using fluorescence of the culture supernatant as a potential at-line monitoring tool to measure the concentration of a recombinant therapeutic protein expressed in a Pichia pastoris fed-batch fermentation. We propose an integrated method wherein both the target protein and total protein concentrations are predicted using intrinsic riboflavin fluorescence and extrinsic fluorescence, respectively. The root mean square error for estimating the concentrations of the target protein (using riboflavin fluorescence) and total protein (using extrinsic fluorescence) have been estimated to be <0.1 and <0.2, respectively. The proposed approach has been validated for two different biotherapeutic products, human serum albumin and granulocyte colony stimulating factor, that were expressed using Mut+ and Muts strains of P. pastoris, respectively. The proposed approach is rapid (1 min analysis time, 10 min total with at line sampling) and thus could be a significant enabler for process analytical technology implementation in Pichia fermentation.

Humanizing glycosylation pathways in eukaryotic expression systems.

Glycosylation represents the most widespread posttranslational modifications, found in a broad spectrum of natural and therapeutic recombinant proteins. It highly affects bioactivity, site-specificity, stability, solubility, immunogenicity, and serum half-life of glycoproteins. Numerous expression hosts including yeasts, insect cells, transgenic plants, and mammalian cells have been explored for synthesizing therapeutic glycoproteins. However, glycosylation profile of eukaryotic expression systems differs from human. Glycosylation strategies have been proposed for humanizing the glycosylation pathways in expression hosts which is the main theme of this review. Besides, we also highlighted the glycosylation potential of protozoan parasites by emphasizing on the mammalian-like glycosylation potential of Leishmania tarentolae known as Leishmania expression system.

Purification of Antibacterial CHAPK Protein Using a Self-Cleaving Fusion Tag and Its Activity Against Methicillin-Resistant Staphylococcus aureus.

Therapeutic LysK-CHAP is a potent anti-staphylococcal protein that could be utilized as an antibiotic substitute. Intein-mediated protein purification is a reasonable and cost-effective method that is most recently used for recombinant therapeutic protein production. Intein (INT) is the internal parts of the protein that can be separated from the immature protein during protein splicing process. This sequence requires no specific enzyme or cofactor for separation. INT sequence and their characteristic of self-cleavage by thiol induction, temperature, and pH changes are used for protein purification. The current study presents the expression of CHAPK262 domain of LysK gene that is fused with INT/chitin-binding sequence while evaluating its purification procedure and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The coding gene sequence of LysK-CHAP (CHAPK262) in pET22-b was amplified with polymerase chain reaction (PCR); the digested product was then cloned into the pTXB1 vector. Electrophoresis confirmed the cloning accuracy of the gene. The pTXB1-CHAPK262 plasmid was transformed to the Escherichia coli ER2566 (E. coli ER2566) expression strain and analyzed for expression of the recombinant protein by SDS-PAGE and Western blotting methods. Finally, CHAPK262 was purified by chitin affinity column using INT tag technology and confirmed by SDS-PAGE. Lytic activity of the purified protein was investigated by disk diffusion method. Cloning of CHAPK262 into the pTXB1 vector, which comprised INT/chitin-binding sequence, was successfully achieved. The SDS-PAGE data also revealed successful expression of the CHAPK262-INT fusion protein and Western blotting method validated the accuracy of the protein. Moreover, purification of CHAPK262 protein was induced by dithiothreitol (DTT) and confirmed by SDS-PAGE. Finally, inhibition zone in MRAS culture medium confirmed antibacterial activity of the protein. Application of intein-mediated antibacterial protein is an appropriate and streamlined method for one-step purification of CHAPK262 as a therapeutic and antibacterial protein. Self-cleaving tags like intein are cost-effective and could be used as a proper purification method for industrial purposes.

A novel self-cleavable tag Zbasic-∆I-CM and its application in the soluble expression of recombinant human interleukin-15 in Escherichia coli.

Soluble expression of recombinant therapeutic proteins in Escherichia coli (E. coli) has been a challenging task in biopharmaceutical development. In this study, a novel self-cleavable tag Zbasic-intein has been constructed for the soluble expression and purification of a recombinant cytokine, human interleukin-15 (IL-15). We screened several solubilizing tags fused with the self-cleavable Mycobacterium tuberculosis recA mini-intein ∆I-CM and demonstrated that Zbasic tag can significantly improve the solubility of the product with correspondent to the intein activity. The fusion protein "Zbasic-∆I-CM-IL-15" was expressed with high solubility and easily enriched by the cost-effective cation-exchange chromatography. The self-cleavage of the fusion tag Zbasic-∆I-CM was then induced by a pH shift, with an activation energy of 7.48kcal/mol. The mature IL-15 with natural N-terminus was released and further purified by hydrophobic interaction and anion-exchange chromatography. High-resolution reverse-phase high-performance liquid chromatography and mass spectrometry analysis confirmed that the product was of high purity and correct mass. With a CTLL-2 cell proliferation-based assay, the EC50 was evaluated to be of about 0.126ng/mL, similar to the product in clinical trials. By avoiding the time-consuming denaturing-refolding steps in previously reported processes, the current method is efficient and cost-effective. The novel tag Zbasic-∆I-CM can be potentially applied to large-scale manufacturing of recombinant human cytokines as well as other mammalian-sourced proteins in E. coli.

A simple, rapid method for evaluation of transfection efficiency based on fluorescent dye

ABSTRACTEnhanced transfection efficiency of transient gene expression (TGE) and electroporation is a useful approach for improvement of recombinant therapeutic proteins in mammalian cells. A novel method is described here in which CHO cells expressing recombinant FVII (rFVII) were labeled with fluorescent dye and analyzed by confocal microscopy. Cells with or without rFVII encoding gene were detectable by flow cytometry. Thus, we were able to distinguish positive cells (with rFVII encoding gene) and quantify their percentages. We evaluated the effects of varying electroporation conditions (voltage, number of repetitions, plasmid amount, carrier DNA) in order to optimize transfection efficiency. The highest transfection efficiency achieved was ∼86%. The method described here allows rapid evaluation of transfection efficiency without co-expression of reporter genes. In combination with appropriate antibodies, the method can be extended to evaluation of transfection efficiency in cells expressing other recombinant proteins.

Integration of cell harvest with affinity-enhanced purification of monoclonal antibodies using aqueous two-phase systems with a dual tag ligand

Abstract Monoclonal antibodies (mAbs) are currently the most important class of recombinant protein therapeutics in the biotechnological and biopharmaceutical industry with more than 250 therapeutic mAbs currently undergoing clinical trials. High titer producing cultures and complex mixtures containing high cell densities, together with an increasing growing demand for highly pure mAbs is making recovery and purification processes hot targets for improvement and opens important technological challenges in mAbs manufacturing platforms. This work explores the use of an affinity dual ligand based on a choline binding polypeptide tag (C-LytA) fused to the synthetic antibody binding Z domain (LYTAG-Z) in aqueous two-phase systems (ATPS) composed of phase forming polymers able to bind to the choline binding site of C-LytA (polyethylene glycol -PEG- and thermosensitive polymers -EOPO) for mAbs selective extraction. Integration of harvesting and ATPS affinity extraction steps were evaluated with ATPS proving to be an alternative strategy for integrating the clarification and the primary recovery of mAbs. An extraction yield of 89% and a clarification higher than 95% were achieved using a system composed of 7% PEG 3350 and 6% dextran 500,000.

Characterization of recombinant human granulocyte colony-stimulating factor expression by FT-IR spectroscopy: Studies on thermal induction and media formulation on the stability of the protein secondary structure

ABSTRACTThe Fourier-transform infrared (FT-IR) spectroscopic approach has been employed to understand the recombinant human G-CSF (rhG-CSF) protein accumulation, secondary structure, and thermal stability in Escherichia coli grown under a temperature shift strategy (37 and 28°C) in various media formulations. The choline + sodium pyruvate (37°C) and sodium pyruvate (28°C) formulations have shown the highest inclusion body (IB) accumulation of 0.41 and 0.46 mg/mL, respectively. Furthermore, insights on the structure of the rhG-CSF within IBs and intact cells have been investigated through secondary structure analysis. Thermal stability experiments were also carried out to explain the pattern of the second derivative structure of rhG-CSF. The studies showed that choline + sodium pyruvate formulation has preserved the protein secondary structure even at 82°C. Overall, the FT-IR spectroscopic technique can also be adopted to accelerate the characterization of other recombinant therapeutic proteins of E. coli origin.

Leishmania-based expression systems.

Production of therapeutic or medical recombinant proteins, such as monoclonal antibodies, proteins, or active enzymes, requires a highly efficient system allowing natural folding and perfect post-translation modifications of the expressed protein. These requirements lead to the generation of a variety of gene expression systems from bacteria to eukaryotes. To achieve the best form of eukaryotic proteins, two factors need to be taken into consideration: choosing a suitable organism to express the protein of interest, and selecting an efficient delivery system. For this reason, the expression of recombinant proteins in eukaryotic nonpathogenic Leishmania parasites is an interesting approach which meets both criteria. Here, new Leishmania-based expression systems are compared with current systems that have long histories in research and industry.

A hybrid approach identifies metabolic signatures of high-producers for chinese hamster ovary clone selection and process optimization.

In-depth characterization of high-producer cell lines and bioprocesses is vital to ensure robust and consistent production of recombinant therapeutic proteins in high quantity and quality for clinical applications. This requires applying appropriate methods during bioprocess development to enable meaningful characterization of CHO clones and processes. Here, we present a novel hybrid approach for supporting comprehensive characterization of metabolic clone performance. The approach combines metabolite profiling with multivariate data analysis and fluxomics to enable a data-driven mechanistic analysis of key metabolic traits associated with desired cell phenotypes. We applied the methodology to quantify and compare metabolic performance in a set of 10 recombinant CHO-K1 producer clones and a host cell line. The comprehensive characterization enabled us to derive an extended set of clone performance criteria that not only captured growth and product formation, but also incorporated information on intracellular clone physiology and on metabolic changes during the process. These criteria served to establish a quantitative clone ranking and allowed us to identify metabolic differences between high-producing CHO-K1 clones yielding comparably high product titers. Through multivariate data analysis of the combined metabolite and flux data we uncovered common metabolic traits characteristic of high-producer clones in the screening setup. This included high intracellular rates of glutamine synthesis, low cysteine uptake, reduced excretion of aspartate and glutamate, and low intracellular degradation rates of branched-chain amino acids and of histidine. Finally, the above approach was integrated into a workflow that enables standardized high-content selection of CHO producer clones in a high-throughput fashion. In conclusion, the combination of quantitative metabolite profiling, multivariate data analysis, and mechanistic network model simulations can identify metabolic traits characteristic of high-performance clones and enables informed decisions on which clones provide a good match for a particular process platform. The proposed approach also provides a mechanistic link between observed clone phenotype, process setup, and feeding regimes, and thereby offers concrete starting points for subsequent process optimization. Biotechnol. Bioeng. 2016;113: 2005-2019. © 2016 Wiley Periodicals, Inc.

Augmenting Chinese hamster genome assembly by identifying regions of high confidence

Chinese hamster Ovary (CHO) cell lines are the dominant industrial workhorses for therapeutic recombinant protein production. The availability of genome sequence of Chinese hamster and CHO cells will spur further genome and RNA sequencing of producing cell lines. However, the mammalian genomes assembled using shot-gun sequencing data still contain regions of uncertain quality due to assembly errors. Identifying high confidence regions in the assembled genome will facilitate its use for cell engineering and genome engineering. We assembled two independent drafts of Chinese hamster genome by de novo assembly from shotgun sequencing reads and by re-scaffolding and gap-filling the draft genome from NCBI for improved scaffold lengths and gap fractions. We then used the two independent assemblies to identify high confidence regions using two different approaches. First, the two independent assemblies were compared at the sequence level to identify their consensus regions as "high confidence regions" which accounts for at least 78 % of the assembled genome. Further, a genome wide comparison of the Chinese hamster scaffolds with mouse chromosomes revealed scaffolds with large blocks of collinearity, which were also compiled as high-quality scaffolds. Genome scale collinearity was complemented with EST based synteny which also revealed conserved gene order compared to mouse. As cell line sequencing becomes more commonly practiced, the approaches reported here are useful for assessing the quality of assembly and potentially facilitate the engineering of cell lines.