Advances in animal cell recombinant protein production: GS-NS0 expression system

Modulating antibody effector functions by Fc glycoengineering

Antibody based drugs, including IgG monoclonal antibodies, are an expanding class of therapeutics widely employed to treat cancer, autoimmune and infectious diseases. IgG antibodies have a conserved N-glycosylation site at Asn297 that bears complex type N-glycans which, along with other less conserved N- and O-glycosylation sites, fine-tune effector functions, complement activation, and half-life of antibodies. Fucosylation, galactosylation, sialylation, bisection and mannosylation all generate glycoforms that interact in a specific manner with different cellular antibody receptors and are linked to a distinct functional profile. Antibodies, including those employed in clinical settings, are generated with a mixture of glycoforms attached to them, which has an impact on their efficacy, stability and effector functions. It is therefore of great interest to produce antibodies containing only tailored glycoforms with specific effects associated with them. To this end, several antibody engineering strategies have been developed, including the usage of engineered mammalian cell lines, in vitro and in vivo glycoengineering.

Screening Strategies for High-Yield Chinese Hamster Ovary Cell Clones

Chinese hamster ovary (CHO) cells are by far the most commonly used mammalian expression system for recombinant expression of therapeutic proteins in the pharmaceutical industry. The development of high-yield stable cell lines requires processes of transfection, selection, screening and adaptation, among which the screening process requires tremendous time and determines the level of forming highly productive monoclonal cell lines. Therefore, how to achieve productive cell lines is a major question prior to industrial manufacturing. Cell line development (CLD) is one of the most critical steps in the production of recombinant therapeutic proteins. Generation of high-yield cell clones is mainly based on the time-consuming, laborious process of selection and screening. With the increase in recombinant therapeutic proteins expressed by CHO cells, CLD has become a major bottleneck in obtaining cell lines for manufacturing. The basic principles for CLD include preliminary screening for high-yield cell pool, single-cell isolation and improvement of productivity, clonality and stability. With the development of modern analysis and testing technologies, various screening methods have been used for CLD to enhance the selection efficiency of high-yield clonal cells. This review provides a comprehensive overview on preliminary screening methods for high-yield cell pool based on drug selective pressure. Moreover, we focus on high throughput methods for isolating high-yield cell clones and increasing the productivity and stability, as well as new screening strategies used for the biopharmaceutical industry.

Mammalian Cell Culture as a Platform for Veterinary Vaccines

For more than three decades, mammalian cells have been the host par excellence for the recombinant protein production for therapeutic purposes in humans. Due to the high cost of media and other supplies used for cell growth, initially this expression platform was only used for the production of proteins of pharmaceutical importance including antibodies. However, large biotechnological companies that used this platform continued research to improve its technical and economic feasibility. The main qualitative improvement was obtained when individual cells could be cultured in a liquid medium similar to bacteria and yeast cultures. Another important innovation for growing cells in suspension was the improvement in chemically defined media that does not contain macromolecules; they were cheaper to culture as any other microbial media. These scientific milestones have reduced the cost of mammalian cell culture and their use in obtaining proteins for veterinary use. The ease of working with mammalian cell culture has permitted the use of this expression platform to produce active pharmaceutic ingredients for veterinary vaccines. In this chapter, the protocol to obtain recombinant mammalian cell lines will be described.

The tobacco phosphatidylethanolamine-binding protein NtFT4 simultaneously improves vitality, growth, and protein yield in human cells

The production of biopharmaceutical proteins in mammalian cells by transient expression or stable transformation requires robust and viable cells. Cell line engineering must therefore balance improved cell growth and viability with high productivity. We tested the ability of nonmammalian phosphatidylethanolamine-binding proteins to enhance cell proliferation in monolayers and suspension cultures. The tobacco protein NtFT4 improved the proliferation of multiple human cell lines. Viable cell density is usually impaired by efficient transfection, but we found that the number of HEK-293TNtFT4 cells at the peak of protein expression was twice that of standard HEK-293T cells, and the antibody yield increased by approximately one-third. Improved growth and viability were observed in different cell lines, in different culture media, and also after transient transfection, suggesting the beneficial trait is consistent and transferable. Additional modifications could boost the productivity of high-density HEK-293TNtFT4 cells even further as we showed for a fluorescent marker protein and recombinant antibody expressed in monolayer cultures. The HEK-293TNtFT4 cell line provides a new human model platform that increases cell proliferation, also achieving a fundamental improvement in recombinant protein expression.

Rapid Purification of Immunoglobulin G Using a Protein A-​immobilized Monolithic Spin Column with Hydrophilic Polymers

A rapid purification method was developed for antibody production in Chinese hamster ovary (CHO) cells using a Protein A-immobilized monolithic silica spin column with hydrophilic polymers. Monolithic silica modified with copolymers of 2-hydroxyethylmethacrylate (HEMA) and glycidyl methacrylate (GMA) showed lower non-specific protein absorption than that modified with a silane reagent. The epoxy group of GMA was converted to an amino group, and Protein A was modified by the coupling reagent. The amount of immobilized Protein A was controlled by changing the ratio of GMA to HEMA and the mesopore size of monolith. A modified monolith disk was fixed to a spin column for rapid antibody purification. The linear curves (for the antibody concentrations over 10 - 300 μg/mL) had a correlation coefficient of >0.999. Our column had various analytical advantages over previously reported columns, including a shorter preparation time (<10 min) and smaller sample volumes for purification with Protein A-immobilized agarose.

Towards Enhancing Therapeutic Glycoprotein Bioproduction: Interventions in the PI3K/AKT/mTOR Pathway

Recombinant glycoproteins produced in mammalian cells are clinically indispensable drugs used to treat a broad spectrum of diseases. Their bio-manufacturing process is laborious, time consuming, and expensive. Investment in expediting the process and reducing its cost is the subject of continued research. The PI3K/Akt/mTOR signaling pathway is a key regulator of diverse physiological functions such as proliferation, global protein, and lipid synthesis as well as many metabolic pathways interacting to increase secretory capabilities. In this review we detail various strategies previously employed to increase glycoprotein production yields via either genetic or pharmacological over-activation of the PI3K/Akt/mTOR pathway, and we discuss their potential and limitations.Key words: mTORC1, CRISPR, specific productivity, translation.

The role of magnetic field in the biopharmaceutical production: Current perspectives

Current scientific evidence on the influence of magnetic field on mammalian cell lines used for industrial production of biopharmaceuticals, on human cell lines and on potential cell lines for the biopharmaceutical production is presented in this review. A novel magnetic coupling induced agitation could be the best solution to eliminate sources of contamination in stirred tank bioreactors which is especially important for mammalian cell cultures. Nevertheless, the side effect of magnetically-coupled stirring mechanism is that cells are exposed to the generated magnetic field. The influence of magnetic field on biological systems has been investigated for several decades. The research continues nowadays as well, investigating the influence of various types of magnetic field in a variety of experimental setups. In the context of bioreactors, only the lower frequencies and intensities of the magnetic field are relevant.

Rapid characterization of secreted recombinant proteins by native mass spectrometry

Characterization of overexpressed proteins is essential for assessing their quality, and providing input for iterative redesign and optimization. This process is typically carried out following purification procedures that require pronounced cost of time and labor. Therefore, quality assessment of recombinant proteins with no prior purification offers a major advantage. Here, we report a native mass spectrometry method that enables characterization of overproduced proteins directly from culture media. Properties such as solubility, molecular weight, folding, assembly state, overall structure, post-translational modifications and binding to relevant biomolecules are immediately revealed. We show the applicability of the method for in-depth characterization of secreted recombinant proteins from eukaryotic systems such as yeast, insect, and human cells. This method, which can be readily extended to high-throughput analysis, considerably shortens the time gap between protein production and characterization, and is particularly suitable for characterizing engineered and mutated proteins, and optimizing yield and quality of overexpressed proteins.

Improving Immunotherapy Through Glycodesign

Immunotherapy is revolutionizing health care, with the majority of high impact "drugs" approved in the past decade falling into this category of therapy. Despite considerable success, glycosylation-a key design parameter that ensures safety, optimizes biological response, and influences the pharmacokinetic properties of an immunotherapeutic-has slowed the development of this class of drugs in the past and remains challenging at present. This article describes how optimizing glycosylation through a variety of glycoengineering strategies provides enticing opportunities to not only avoid past pitfalls, but also to substantially improve immunotherapies including antibodies and recombinant proteins, and cell-based therapies. We cover design principles important for early stage pre-clinical development and also discuss how various glycoengineering strategies can augment the biomanufacturing process to ensure the overall effectiveness of immunotherapeutics.

Energy-based culture medium design for biomanufacturing optimization: A case study in monoclonal antibody production by GS-NS0 cells

Demand for high-value biologics, a rapidly growing pipeline, and pressure from competition, time-to-market and regulators, necessitate novel biomanufacturing approaches, including Quality by Design (QbD) principles and Process Analytical Technologies (PAT), to facilitate accelerated, efficient and effective process development platforms that ensure consistent product quality and reduced lot-to-lot variability. Herein, QbD and PAT principles were incorporated within an innovative in vitro-in silico integrated framework for upstream process development (UPD). The central component of the UPD framework is a mathematical model that predicts dynamic nutrient uptake and average intracellular ATP content, based on biochemical reaction networks, to quantify and characterize energy metabolism and its adaptive response, metabolic shifts, to maintain ATP homeostasis. The accuracy and flexibility of the model depends on critical cell type/product/clone-specific parameters, which are experimentally estimated. The integrated in vitro-in silico platform and the model's predictive capacity reduced burden, time and expense of experimentation resulting in optimal medium design compared to commercially available culture media (80% amino acid reduction) and a fed-batch feeding strategy that increased productivity by 129%. The framework represents a flexible and efficient tool that transforms, improves and accelerates conventional process development in biomanufacturing with wide applications, including stem cell-based therapies.

Impact of host cell line choice on glycan profile

Protein glycosylation is post-translational modification (PTM) which is important for pharmacokinetics and immunogenicity of recombinant glycoprotein therapeutics. As a result of variations in monosaccharide composition, glycosidic linkages and glycan branching, glycosylation introduces considerable complexity and heterogeneity to therapeutics. The host cell line used to produce the glycoprotein has a strong influence on the glycosylation because different host systems may express varying repertoire of glycosylation enzymes and transporters that contributes to specificity and heterogeneity in glycosylation profiles. In this review, we discuss the types of host cell lines currently used for recombinant therapeutic production, their glycosylation potential and the resultant impact on glycoprotein properties. In addition, we compare the reported glycosylation profiles of four recombinant glycoproteins: immunoglobulin G (IgG), coagulation factor VII (FVII), erythropoietin (EPO) and alpha-1 antitrypsin (A1AT) produced in different mammalian cells to establish the influence of mammalian host cell lines on glycosylation.

The enhancement of antibody concentration and achievement of high cell density CHO cell cultivation by adding nucleoside

Recently, with the dramatic increase in demand for therapeutic antibodies, Chinese hamster ovary (CHO) cell culture systems have made significant progress in recombinant antibody production. Over the past two decades, recombinant antibody productivity has been improved by more than 100-fold. Medium optimization has been identified as an important key approach for increasing product concentrations. In this study, we evaluated the effects of deoxyuridine addition to fed-batch cultures of antibody-expressing CHO cell lines. Furthermore, we investigated the effects of combined addition of deoxyuridine, thymidine, and deoxycytidine. Our results suggest that addition of these pyrimidine nucleosides can increase CHO cell growth, with no significant change in the specific production rate. As a result of the increased cell growth, the antibody concentration was elevated and we were able to achieve more than 9 g/L during 16 days of culture. Similar effects of nucleoside addition were observed in fed-batch cultures of a Fab fragment-expressing CHO cell line, and the final Fab fragment concentration was more than 4 g/L. This nucleoside addition strategy could be a powerful platform for efficient antibody production.

Human cell lines for biopharmaceutical manufacturing: history, status, and future perspectives

Biotherapeutic proteins represent a mainstay of treatment for a multitude of conditions, for example, autoimmune disorders, hematologic disorders, hormonal dysregulation, cancers, infectious diseases and genetic disorders. The technologies behind their production have changed substantially since biotherapeutic proteins were first approved in the 1980s. Although most biotherapeutic proteins developed to date have been produced using the mammalian Chinese hamster ovary and murine myeloma (NS0, Sp2/0) cell lines, there has been a recent shift toward the use of human cell lines. One of the most important advantages of using human cell lines for protein production is the greater likelihood that the resulting recombinant protein will bear post-translational modifications (PTMs) that are consistent with those seen on endogenous human proteins. Although other mammalian cell lines can produce PTMs similar to human cells, they also produce non-human PTMs, such as galactose-α1,3-galactose and N-glycolylneuraminic acid, which are potentially immunogenic. In addition, human cell lines are grown easily in a serum-free suspension culture, reproduce rapidly and have efficient protein production. A possible disadvantage of using human cell lines is the potential for human-specific viral contamination, although this risk can be mitigated with multiple viral inactivation or clearance steps. In addition, while human cell lines are currently widely used for biopharmaceutical research, vaccine production and production of some licensed protein therapeutics, there is a relative paucity of clinical experience with human cell lines because they have only recently begun to be used for the manufacture of proteins (compared with other types of cell lines). With additional research investment, human cell lines may be further optimized for routine commercial production of a broader range of biotherapeutic proteins.

Understanding central carbon metabolism of rapidly proliferating mammalian cells based on analysis of key enzymatic activities in GS-CHO cell lines

The central carbon metabolism (glycolysis, the pentose phosphate pathway [PPP], and the tricarboxylic acid [TCA] cycle) plays an essential role in the supply of biosynthetic precursors and energy. How the central carbon metabolism changes with the varying growth rates in the in vitro cultivation of rapidly proliferating mammalian cells, such as cancer cells and continuous cell lines for recombinant protein production, remains elusive. Based on relationships between the growth rate and the activity of seven key enzymes from six cell clones, this work reports finding an important metabolic characteristic in rapidly proliferating glutamine synthetase-Chinese hamster ovary cells. The key enzymatic activity involved in the TCA cycle that is responsible for the supply of energy became elevated as the growth rate exhibited increases, while the activity of key enzymes in metabolic pathways (glycolysis and the PPP), responsible for the supply of biosynthetic precursors, tended to decrease-suggesting that rapidly proliferating cells still depended predominantly on the TCA cycle rather than on aerobic glycolysis for their energetic demands. Meanwhile, the growth-limiting resource was most likely biosynthetic substrates rather than energy provision. In addition, the multifaceted role of glucose-6-phosphate isomerase (PGI) was confirmed, based on a significant correlation between PGI activity and the percentage of G2/M-phase cells.

Immunogenomic engineering of a plug-and-(dis)play hybridoma platform

Hybridomas, fusions of primary mouse B cells and myelomas, are stable, rapidly-proliferating cell lines widely utilized for antibody screening and production. Antibody specificity of a hybridoma clone is determined by the immunoglobulin sequence of the primary B cell. Here we report a platform for rapid reprogramming of hybridoma antibody specificity by immunogenomic engineering. Here we use CRISPR-Cas9 to generate double-stranded breaks in immunoglobulin loci, enabling deletion of the native variable light chain and replacement of the endogenous variable heavy chain with a fluorescent reporter protein (mRuby). New antibody genes are introduced by Cas9-targeting of mRuby for replacement with a donor construct encoding a light chain and a variable heavy chain, resulting in full-length antibody expression. Since hybridomas surface express and secrete antibodies, reprogrammed cells are isolated using flow cytometry and cell culture supernatant is used for antibody production. Plug-and-(dis)play hybridomas can be reprogrammed with only a single transfection and screening step.

Towards unravelling the kinetics of an acute myeloid leukaemia model system under oxidative and starvation stress: a comparison between two- and three-dimensional cultures

A great challenge when conducting ex vivo studies of leukaemia is the construction of an appropriate experimental platform that would recapitulate the bone marrow (BM) environment. Such a 3D scaffold system has been previously developed in our group [1]. Additionally to the BM architectural characteristics, parameters such as oxygen and glucose concentration are crucial as their value could differ between patients as well as within the same patient at different stages of treatment, consequently affecting the resistance of leukaemia to chemotherapy. The effect of oxidative and glucose stress-at levels close to human physiologic ones-on the proliferation and metabolic evolution of an AML model system (K-562 cell line) in conventional 2D cultures as well as in 3D scaffolds were studied. We observed that the K-562 cell line can proliferate and remain alive for 2 weeks in medium with glucose close to physiological levels both in 20 and 5% O2. We report interesting differences on the cellular response to the environmental, i.e., oxidative and/or nutritional stress stimuli in 2D and 3D. Higher adaptation to oxidative stress under non-starving conditions is observed in the 3D system. The glucose level in the medium has more impact on the cellular proliferation in the 3D compared to the 2D system. These differences can be of significant importance both when applying chemotherapy in vitro and also when constructing mathematical tools for optimisation of disease treatment.

Cyclin and DNA distributed cell cycle model for GS-NS0 cells

Mammalian cell cultures are intrinsically heterogeneous at different scales (molecular to bioreactor). The cell cycle is at the centre of capturing heterogeneity since it plays a critical role in the growth, death, and productivity of mammalian cell cultures. Current cell cycle models use biological variables (mass/volume/age) that are non-mechanistic, and difficult to experimentally determine, to describe cell cycle transition and capture culture heterogeneity. To address this problem, cyclins-key molecules that regulate cell cycle transition-have been utilized. Herein, a novel integrated experimental-modelling platform is presented whereby experimental quantification of key cell cycle metrics (cell cycle timings, cell cycle fractions, and cyclin expression determined by flow cytometry) is used to develop a cyclin and DNA distributed model for the industrially relevant cell line, GS-NS0. Cyclins/DNA synthesis rates were linked to stimulatory/inhibitory factors in the culture medium, which ultimately affect cell growth. Cell antibody productivity was characterized using cell cycle-specific production rates. The solution method delivered fast computational time that renders the model's use suitable for model-based applications. Model structure was studied by global sensitivity analysis (GSA), which identified parameters with a significant effect on the model output, followed by re-estimation of its significant parameters from a control set of batch experiments. A good model fit to the experimental data, both at the cell cycle and viable cell density levels, was observed. The cell population heterogeneity of disturbed (after cell arrest) and undisturbed cell growth was captured proving the versatility of the modelling approach. Cell cycle models able to capture population heterogeneity facilitate in depth understanding of these complex systems and enable systematic formulation of culture strategies to improve growth and productivity. It is envisaged that this modelling approach will pave the model-based development of industrial cell lines and clinical studies.

On-chip microelectrode impedance analysis of mammalian cell viability during biomanufacturing

The characterization of cell viability is a challenging task in applied biotechnology, as no clear definition of cell death exists. Cell death is accompanied with a change in the electrical properties of the membrane as well as the cell interior. Therefore, changes in the physiology of cells can be characterized by monitoring of their dielectric properties. We correlated the dielectric properties of industrially used mammalian cells, sedimented over interdigitated microelectrodes, to the AC signal response across the chip. The voltage waveforms across the electrodes were processed to obtain the circuit impedance, which was used to quantify the changes in cell viability. We observed an initial decrease in impedance, after which it remained nearly constant. The results were compared with data from the dye exclusion viability test, the cell specific oxygen uptake rate, and the online viable cell density data from capacitance probes. The microelectrode technique was found to be sensitive to physiological changes taking place inside the cells before their membrane integrity is compromised. Such accurate determination of the metabolic status during this initial period, which turned out to be less well captured in the dye exclusion tests, may be essential for several biotechnology operations.

The choice of mammalian cell host and possibilities for glycosylation engineering

Non-human mammalian cells such as CHO have been used predominantly for the production of biopharmaceuticals including monoclonal antibodies (Mabs). Although the glycosylation profile of these products is 'human-like' there is still the possibility of immunogenic epitopes such as α-Gal and Neu5Gc. Human cell lines have now been designed for high productivity of recombinant proteins and ensuring authentic glycosylation patterns. The control of glycosylation on such proteins is important for the efficacy of recombinant biopharmaceuticals as well as the immunogenic properties of viral vaccines such as influenza. We are now starting to understand some of the relationships between the structure of glycans and the function bestowed on the associated protein. This has promoted cell culture technologies for the targeted control of glycosylation to produce pre-determined glycan profiles of secreted products.

Over-expression of secreted proteins from mammalian cell lines

Secreted mammalian proteins require the development of robust protein over-expression systems for crystallographic and biophysical studies of protein function. Due to complex disulfide bonds and distinct glycosylation patterns preventing folding and expression in prokaryotic expression hosts, many secreted proteins necessitate production in more complex eukaryotic expression systems. Here, we elaborate on the methods used to obtain high yields of purified secreted proteins from transiently or stably transfected mammalian cell lines. Among the issues discussed are the selection of appropriate expression vectors, choice of signal sequences for protein secretion, availability of fusion tags for enhancing protein stability and purification, choice of cell line, and the large-scale growth of cells in a variety of formats.

Recent advances in mammalian protein production

Mammalian protein production platforms have had a profound impact in many areas of basic and applied research, and an increasing number of blockbuster drugs are recombinant mammalian proteins. With global sales of these drugs exceeding US$120 billion per year, both industry and academic research groups continue to develop cost effective methods for producing mammalian proteins to support pre-clinical and clinical evaluations of potential therapeutics. While a wide range of platforms have been successfully exploited for laboratory use, the bulk of recent biologics have been produced in mammalian cell lines due to the requirement for post translational modification and the biosynthetic complexity of the target proteins. In this review we highlight the range of mammalian expression platforms available for recombinant protein production, as well as advances in technologies for the rapid and efficient selection of highly productive clones.

Protein production from the structural genomics perspective: achievements and future needs

Despite a multitude of recent technical breakthroughs speeding high-resolution structural analysis of biological macromolecules, production of sufficient quantities of well-behaved, active protein continues to represent the rate-limiting step in many structure determination efforts. These challenges are only amplified when considered in the context of ongoing structural genomics efforts, which are now contending with multi-domain eukaryotic proteins, secreted proteins, and ever-larger macromolecular assemblies. Exciting new developments in eukaryotic expression platforms, including insect and mammalian-based systems, promise enhanced opportunities for structural approaches to some of the most important biological problems. Development and implementation of automated eukaryotic expression techniques promises to significantly improve production of materials for structural, functional, and biomedical research applications.

Mouse cell line authentication

The scientific community has responded to the misidentification of human cell lines with validated methods to authenticate these cells; however, few assays are available for nonhuman cell line identification. We have developed a multiplex polymerase chain reaction assay that targets nine tetranucleotide short tandem repeat (STR) markers in the mouse genome. Unique profiles were obtained from seventy-two mouse samples that were used to determine the allele distribution for each STR marker. Correlations between allele fragment length and repeat number were determined with DNA Sanger sequencing. Genotypes for L929 and NIH3T3 cell lines were shown to be stable with increasing passage numbers as there were no significant differences in fragment length with samples of low passage when compared to high passage samples. In order to detect cell line contaminants, primers for two human STR markers were incorporated into the multiplex assay to facilitate detection of human and African green monkey DNA. This multiplex assay is the first of its kind to provide a unique STR profile for each individual mouse sample and can be used to authenticate mouse cell lines.

Pharmacokinetic and pharmacodynamic properties of canakinumab, a human anti-interleukin-1β monoclonal antibody

Canakinumab is a high-affinity human monoclonal anti-interleukin-1β (IL-1β) antibody of the IgG1/κ isotype designed to bind and neutralize the activity of human IL-1β, a pro-inflammatory cytokine. Canakinumab is currently being investigated on the premise that it would exert anti-inflammatory effects on a broad spectrum of diseases, driven by IL-1β. This paper focuses on the analysis of the pharmacokinetic and pharmacodynamic data from the canakinumab clinical development programme, describing results from the recently approved indication for the treatment of cryopyrin-associated periodic syndromes (CAPS) under the trade name ILARIS®, as well as diseases such as rheumatoid arthritis, asthma and psoriasis. Canakinumab displays pharmacokinetic properties typical of an IgG1 antibody. In a CAPS patient weighing 70 kg, slow serum clearance (0.174 L/day) was observed with a low total volume of distribution at steady state (6.0 L), resulting in a long elimination half-life of 26 days. The subcutaneous absolute bioavailability was high (70%). Canakinumab displays linear pharmacokinetics, with a dose-proportional increase in exposure and no evidence of accelerated clearance or time-dependent changes in pharmacokinetics following repeated administration was observed. The pharmacokinetics of canakinumab in various diseases (e.g. CAPS, rheumatoid arthritis, psoriasis or asthma) are comparable to those in healthy individuals. No sex- or age-related pharmacokinetic differences were observed after correction for body weight. An increase in total IL-1β was observed in both healthy subjects and all patient populations following canakinumab dosing, reflecting the ability of canakinumab to bind circulating IL-1β. The kinetics of total IL-1β along with the pharmacokinetics of canakinumab were characterized by a population-based pharmacokinetic-binding model, where the apparent in vivo dissociation constant, signifying binding affinity of canakinumab to circulating IL-1β, was estimated at 1.07 ± 0.173 nmol/L in CAPS patients. During development of canakinumab a cell line change was introduced. Pharmacokinetic characterization was performed in both animals and humans to assure that this manufacturing change did not affect the pharmacokinetic/pharmacodynamic properties of canakinumab.

Immunophenotyping of classic murine myeloma cell lines used for monoclonal antibody production

Murine myeloma cell lines play an important role in different areas of scientific research and are essential tools for monoclonal antibody production technology. Thus, it is important to understand the biology of these cell lines in order to provide useful information to various research fronts. The present study aims to perform detailed analyses of surface antigens expressed on three major murine myeloma cell lines extensively used for MAb production. The P3X63Ag8.653 cell line expresses molecules associated with T cell interaction (CD40(low), CD80(low)), as well as antigens related to plasma cell phenotype (CD138(high), CD184(low)). The Sp2/0-Ag14 cell line presents molecules associated with BCR activation and regulation (CD79b(low), CD22(low), CD72(med)), molecules related to T cell interaction (CD40(low), CD80(low)), and markers of plasma cell phenotype (CD138(high), CD184(low)). The NS1 cell line presents all molecules of plasma cell phenotype evaluated in this study (CD184(low), CD138(high), CD38(med)) with low expression of CD72 (CD72(low)), a molecule related to BCR activation. Molecules associated with immune response modulation such as CD23 and CD25, as well as CD117, a marker related to undifferentiated cell phenotype, were not observed in any of the three murine myeloma cell lines evaluated. These data show that in spite of their common origin and function, the immunological profiles differ between P3X63Ag8.653, Sp2/0-Ag14, and NS1 cell lines.

Monoclonal antibody expression in mammalian cells

In the past two decades, the production levels for monoclonal antibodies in mammalian expression systems have improved dramatically. Single cell productivity for monoclonal antibodies has increased 20-50 fold due to the improvements in expression hosts, expression vectors, cell culture media, and production processes. However, most of these improvements are proprietary to large pharmaceutical/biotech companies and involve large steel-tank bioreactors. Therefore, these processes are difficult for small companies and academic labs to reproduce. Transient expression in mammalian cells has recently been used very widely for monoclonal antibody expression. Cell line and expression vector engineering increased expression levels to several hundred milligrams per liter. The availability of highly effective transfection reagents and disposable bioreactors make the transient expression process an efficient and cost-effective way to make recombinant antibodies in large quantity. Here, we describe the protocols for small- to mid-scale transient expression of monoclonal antibodies in shake-flasks and for large-scale production in WAVE bioreactors.

Effect of different UCOE-promoter combinations in creation of engineered cell lines for the production of Factor VIII

Background

The most common approach used in generating cell lines for the production of therapetic proteins relies on gene amplification induced by a drug resistance gene e. g., DHFR and glutamine synthetase. Practically, this results in screening large number of clones for the one that expresses high levels of the biologic in a stable manner. The inefficiency of mammalian vector systems to express proteins in a stable manner typically involves silencing of the exogenous gene resulting from modifications such as methylation of CpG DNA sequences, histone deacetylation and chromatin condensation. The use of un-methylated CpG island fragments from housekeeping genes referred to as UCOE (ubiquitous chromatin opening elements) in plasmid vectors is now well established for increased stability of transgene expression. However, few UCOE-promoter combinations have been studied to date and in this report we have tested 14 different combinations.

Findings

In this report we describe studies with two different UCOEs (the 1.5 Kb human RNP fragment and the 3.2 Kb mouse RPS3 fragment) in combination with various promoters to express a large protein (B domain deleted factor VIII; BDD-FVIII) in a production cell line, BHK21. We show here that there are differences in expression of BDD-FVIII by the different UCOE-promoter combinations in both attached and serum free suspension adapted cells. In all cases, the 1.5 Kb human RNP UCOE performed better in expressing BDD-FVIII than their corresponding 3.2 Kb mouse RPS3 UCOE. Surprisingly, in certain scenarios described here, expression from a number of promoters was equivalent or higher than the commonly used and industry standard human CMV promoter.

Conclusion

This study indicates that certain UCOE-promoter combinations are better than others in expressing the BDD-FVIII protein in a stable manner in BHK21 cells. An empirical study such as this is required to determine the best combination of UCOE-promoter in a vector for a particular production cell line.

Towards the molecular characterization of the stable producer phenotype of recombinant antibody-producing NS0 myeloma cells

The loss of heterologous protein expression is one of the major problems faced by industrial cell line developers and has been reported by several authors. Therefore, the understanding of the mechanisms involved in the generation of stable and high producer cell lines is a critical issue, especially for those processes based on long term continuous cultures. We characterized two recombinant NS0 myeloma cell lines expressing Nimotuzumab, a humanized anti-human epidermal growth factor receptor (EGFR) antibody. The hR3/H7 clone is a stable producer obtained from the unstable hR3/t16 clone. The unstable clone was characterized by a bimodal distribution of intracellular immunoglobulin staining using flow cytometry. Loss of antibody production was due to the emergence of a non-producer cell subpopulation that increased with cell generation number. Immunoglobulin heavy chain (HC) and light chain (LC) ratio (HC/LC) was lower for the unstable phenotype. Proteomic maps using two dimensional gel electrophoresis (2DE) were obtained for both clones, at initial cell culture time and after 40 generations. Fifteen proteins potentially associated with the phenomenon of production stability were identified. The hR3/H7 stable clone showed an up-regulated expression pattern for most of these proteins. The regulation of recombinant antibody production by the host NS0 myeloma cell line most likely involves simultaneously cellular processes such as DNA transcription, mRNA processing, protein synthesis and folding, vesicular transport, glycolysis and energy production, according to the proteins identified in the present proteomic study.

Protein glycosylation and its impact on biotechnology

Glycosylation is a post-translational modification that is of paramount importance in the production of recombinant pharmaceuticals as most recombinantly produced therapeutics are N- and/or O-glycosylated. Being a cell-system-dependent process, it also varies with expression systems and growth conditions, which result in glycan microheterogeneity and macroheterogeneity. Glycans have an effect on drug stability, serum half-life, and immunogenicity; it is therefore important to analyze and optimize the glycan decoration of pharmaceuticals. This review summarizes the aspects of protein glycosylation that are of interest to biotechnologists, namely, biosynthesis and biological relevance, as well as the tools to optimize and to analyze protein glycosylation.