Production of recombinant protein therapeutics in cultivated mammalian cells

Metabolomics of Chinese Hamster Ovary Cells

Increasing demand of protein biotherapeutics produced using Chinese hamster ovary (CHO) cell lines necessitates improvement in the production yield of the bioprocess. Various cell engineering, improved media formulation and process-design based approaches utilizing the power of OMICS technologies, specifically, genomics and proteomics, have been employed; however, the potential of metabolomics largely remains unexplored. Metabolomics enables the detection, identification, and/or quantitation of small molecules, commonly known as metabolites, in and around the cells and may help to unlock the cellular molecular mechanism(s) that regulates cell growth and productivity in the bioprocess and improves cellular performance during the bioprocess. Currently, liquid chromatography (LC)/gas chromatography (CG)- coupled with mass-spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy are the most commonly used approaches for metabolomics. Therefore, in this chapter, we have discussed the standard procedures of investigating CHO metabolites using LC/GC-MS and/or NMR-based approaches.

Application of CRISPR/Cas9 Genome Editing to Improve Recombinant Protein Production in CHO Cells

Genome editing has become an important aspect of Chinese hamster ovary (CHO) cell line engineering for improving the production of recombinant protein therapeutics. Currently, the engineering focus is directed toward expanding product diversity while controlling and improving product quality and yields. In this chapter, we present our protocol for using the genome editing tool Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) to knock out engineering target genes in CHO cells. As an example, we describe how to knock out the glutamine synthetase (GS) gene, which increases the selection efficiency of the GS-mediated gene amplification system.

Physics-informed neural networks for biopharmaceutical cultivation processes: Consideration of varying process parameter settings

We present a new modeling approach for the study and prediction of important process outcomes of biotechnological cultivation processes under the influence of process parameter variations. Our model is based on physics-informed neural networks (PINNs) in combination with kinetic growth equations. Using Taylor series, multivariate external process parameter variations for important variables such as temperature, seeding cell density and feeding rates can be integrated into the corresponding kinetic rates and the governing growth equations. In addition to previous approaches, PINNs also allow continuous and differentiable functions as predictions for the process outcomes. Accordingly, our results show that PINNs in combination with Taylor-series expansions for kinetic growth equations provide a very high prediction accuracy for important process variables such as cell densities and concentrations as well as a detailed study of individual and combined parameter influences. Furthermore, the proposed approach can also be used to evaluate the outcomes of new parameter variations and combinations, which enables a saving of experiments in combination with a model-driven optimization study of the design space.

Phosphopeptide Enrichment and LC-MS/MS Analysis to Study the Phosphoproteome of Recombinant Chinese Hamster Ovary Cells

The reversible phosphorylation of proteins on serine, threonine, and tyrosine residues is one of the most important post-translational modifications that regulates many biological processes. There have been relatively few studies on the phosphoproteome of recombinant Chinese hamster ovary (CHO) cells to date despite phosphorylation playing a crucial role in regulating many molecular and cellular processes relevant to bioprocess phenotypes including, for example, transcription, translation, growth, apoptosis, and signal transduction. In this chapter, we provide a protocol for phosphoproteomic analysis of CHO cells using phosphopeptide enrichment with metal oxide affinity chromatography (MOAC) and immobilized metal affinity chromatography (IMAC) techniques, followed by site-specific identification of phosphorylated residues using liquid chromatography mass spectrometry (LC-MS), multistage activation (MSA), and MS3 strategies. This protocol can also be used for quantitative phosphoproteomic analysis using both labeled and label-free approaches.

HEK-omics: The promise of omics to optimize HEK293 for recombinant adeno-associated virus (rAAV) gene therapy manufacturing

Gene therapy is poised to transition from niche to mainstream medicine, with recombinant adeno-associated virus (rAAV) as the vector of choice. However, robust, scalable, industrialized production is required to meet demand and provide affordable patient access, which has not yet materialized. Closing the chasm between demand and supply requires innovation in biomanufacturing to achieve the essential step change in rAAV product yield and quality. Omics provides a rich source of mechanistic knowledge that can be applied to HEK293, the most commonly used cell line for rAAV production. In this review, the findings from a growing number of diverse studies that apply genomics, epigenomics, transcriptomics, proteomics, and metabolomics to HEK293 bioproduction are explored. Learnings from CHO-Omics, application of omics approaches to improve CHO bioproduction, provide a framework to explore the potential of "HEK-Omics" as a multi-omics-informed approach providing actionable mechanistic insights for improved transient and stable production of rAAV and other recombinant products in HEK293.

HVTN 123: A Phase 1, Randomized Trial Comparing Safety and Immunogenicity of CH505TF gp120 Produced by Stably and Transiently Transfected Cell Lines

Utilizing transiently transfected cell lines could significantly reduce manufacturing timelines for protein subunit vaccines. This trial compared safety and immunogenicity of human immunodeficiency virus (HIV) envelope CH505TF gp120 vaccines produced by upstream stable and transient transfection (each admixed with GLA-SE adjuvant, a TL4 agonist). Both vaccines were safe and well tolerated. Serum IgG binding antibody response rates 2 weeks after final injection were 92% in the stable group and 93% in the transient group (P = 1.000). Neutralization response rates against CH505.w4.3 were also equivalent (92% vs 100%, P = .291). These data support transient transfection as an available tool for accelerating HIV vaccine testing and iteration. Clinical Trials Registration. NCT03856996.

Tuning plasmid DNA amounts for cost-effective transfections of mammalian cells: when less is more

Transient gene expression (TGE) in mammalian cells is a well-known approach to the fast expression of recombinant proteins. The human cell line HEK (human embryonic kidney) 293F is widely used in this field, due to its adaptability to grow in suspension to high cell densities in serum-free media, amenability to transfection, and production of recombinant proteins in satisfactory quantities for functional and structural analysis. Amounts of plasmid DNA (pDNA) required in transfections for TGE remain high (usually 1 µg pDNA/mL, or even higher), representing a noticeable proportion of the overall cost. Thus, there is an economic need to reduce amounts of coding pDNA in TGE processes. In this work, amounts of both pDNA and transfecting agent used for TGE in HEK 293F cells have been explored in order to reduce them without compromising (or even improving) the productivity of the process in terms of protein yield. In our hands, minimal polyethyleneimine (PEI) cytotoxicity and optimum protein yields were obtained when transfecting at 0.5 µg pDNA/mL (equal to 0.5 µg pDNA/million cells) and a DNA-to-PEI ratio of 1:3, a trend confirmed for several unrelated recombinant proteins. Thus, carefully tuning pDNA and transfecting agent amounts not only reduces the economic costs but also results in higher recombinant protein yields. These results surely have a direct application and interest for the biopharmaceutical industry, always concerned in increasing productivity while decreasing economic costs. KEY POINTS: • Mammalian cells are widely used to produce recombinant proteins in short times. • Tuning DNA and transfecting agent are of great interest to optimize economic costs. • Reducing DNA and transfecting agent amounts result in higher protein yields.

Noncanonical Amino Acid Incorporation in Animals and Animal Cells

Noncanonical amino acids (ncAAs) are synthetic building blocks that, when incorporated into proteins, confer novel functions and enable precise control over biological processes. These small yet powerful tools offer unprecedented opportunities to investigate and manipulate various complex life forms. In particular, ncAA incorporation technology has garnered significant attention in the study of animals and their constituent cells, which serve as invaluable model organisms for gaining insights into human physiology, genetics, and diseases. This review will provide a comprehensive discussion on the applications of ncAA incorporation technology in animals and animal cells, covering past achievements, current developments, and future perspectives.

A multimodal digital microfluidic testing platform for antibody-producing cell lines

In recent years, monoclonal antibodies (mAbs) have become a powerful tool in the treatment of human diseases. Currently, over 100 mAbs have received approval for therapeutic use in the US, with wide-ranging applications from cancer to infectious diseases. The predominant method of producing antibodies for therapeutics involves expression in mammalian cell lines. In the mAb production process, significant optimization is typically done to maximize antibody titres from cells grown in bioreactors. Therefore, systems that can miniaturize and automate cell line testing (e.g., viability and antibody production assays) are valuable in reducing therapeutic mAb development costs. Here we present a novel platform for cell line optimization for mAb production using digital microfluidics. The platform enables testing of cell culture samples in 6-8 μL droplets with semi-automated viability, media pH, and antibody production assays. This system provides a unique bridge between cell growth and productivity metrics, while minimizing culture volume requirements for daily testing. We propose that this technology and its future iterations has the potential to help reduce the time-to-market and development costs of antibody-producing cell lines.

Highly selective split intein method for efficient separation and purification of recombinant therapeutic proteins from mammalian cell culture fluid

Biologics and vaccines have been successfully developed over the last few decades to treat many diseases. Each of these drugs must be highly purified for clinical use. Monoclonal antibodies (mAbs), the dominant therapeutic modality on the market, can be easily purified using the standard Protein A affinity platform. However, no generally applicable affinity platforms are available for the manufacture of other therapeutic proteins for clinical use. Thus, multicolumn chromatography processes for widely being used for product purification. These processes demand significant optimization to meet desired product quality attributes, where each step also decreases final yields. In this work, we demonstrate the novel self-removing iCapTag™ affinity tag, which provides a new platform for capturing, concentrating, and purifying recombinant proteins. Importantly, this system provides a tagless target protein, which is suitable for research and clinical use, where the only requirement for tag removal is a small change in buffer pH. No additional proteins, reagents or cofactors are required. We also present case studies demonstrating the use of iCapTag™ for highly efficient purification of untagged interferon alpha 2b, the ML39 single chain variable fragment (scFv), and the receptor binding domain (RBD) of SARS-CoV-2 spike protein. These proteins were expressed and secreted by Expi293 cells with the self-removing tag fused to their N-terminus. We were able to obtain highly pure (> 99 %) tagless protein in a single purification step with high clearance of host cell DNA, tagged precursor, higher and lower molecular weight impurities. Based on these preliminary results, we propose the iCapTag™ as a universal capture platform for diverse classes of recombinant therapeutic proteins.

A user-friendly fluorescent biosensor for precise lactate detection and quantification in vitro

As a critical metabolite, the standardization of lactate quantification is increasingly crucial. Therefore, we developed LaconicSF, a lactate-responsive biosensor exhibiting exceptional specificity in lactate detection. LaconicSF enables efficient lactate quantification in CHO cell culture medium and holds potential as a user-friendly detection tool for lactate quantification in vitro.

Condition optimization for electroporation transfection in horse skeletal muscle satellite cells

Satellite cells are an important cellular model for studying muscle growth and development and mammalian locomotion-related molecular mechanisms. In this study, we investigated the effects of voltage, pulse duration, and DNA dosage on horse skeletal muscle satellite cells' electroporation transfection efficiency using the eukaryotic expression plasmid Td Tomato-C1 (5.5 kb) encoding the red fluorescent protein gene mainly based on fluorescence-positive cell rate and cell survival rate. By comparison of different voltages, pulse durations, and DNA doses, horse skeletal muscle satellite cells have nearly 80% transfection efficiency under the condition of voltage 120 V, DNA dosage 7 µg/ml, and pulse duration 30 ms. This optimized electroporation condition would facilitate the application of horse skeletal muscle satellite cells in genetic studies of muscle function and related diseases.

Enhanced efficacy of glycoengineered rice cell-produced trastuzumab

For several decades, a plant-based expression system has been proposed as an alternative platform for the production of biopharmaceuticals including therapeutic monoclonal antibodies (mAbs), but the immunogenicity concerns associated with plant-specific N-glycans attached in plant-based biopharmaceuticals has not been completely solved. To eliminate all plant-specific N-glycan structure, eight genes involved in plant-specific N-glycosylation were mutated in rice (Oryza sativa) using the CRISPR/Cas9 system. The glycoengineered cell lines, PhytoRice®, contained a predominant GnGn (G0) glycoform. The gene for codon-optimized trastuzumab (TMab) was then introduced into PhytoRice® through Agrobacterium co-cultivation. Selected cell lines were suspension cultured, and TMab secreted from cells was purified from the cultured media. The amino acid sequence of the TMab produced by PhytoRice® (P-TMab) was identical to that of TMab. The inhibitory effect of P-TMab on the proliferation of the BT-474 cancer cell line was significantly enhanced at concentrations above 1 μg/mL (****P < 0.0001). P-TMab bound to a FcγRIIIa variant, FcγRIIIa-F158, more than 2.7 times more effectively than TMab. The ADCC efficacy of P-TMab against Jurkat cells was 2.6 times higher than that of TMab in an in vitro ADCC assay. Furthermore, P-TMab demonstrated efficient tumour uptake with less liver uptake compared to TMab in a xenograft assay using the BT-474 mouse model. These results suggest that the glycoengineered PhytoRice® could be an alternative platform for mAb production compared to current CHO cells, and P-TMab has a novel and enhanced efficacy compared to TMab.

Procollagen-lysine 2-oxoglutarate 5-dioxygenases are responsible for 5R-hydroxylysine modification of therapeutic T-cell bispecific monoclonal antibodies produced by Chinese hamster ovary cells

We present a detailed mass spectrometric analysis of three 2 + 1 T-cell bispecific monoclonal antibodies (TCB mAbs), where an unexpected +15.9950 Da mass shift in tryptic peptides was observed. This modification was attributed to the occurrence of 5R-hydroxylysine (Hyl) using a hybrid LC-MS/MS molecular characterization and CRISPR/Cas9 gene deletion approach. The modification was found at various sites within TCB mAbs, with a conspicuous hot spot motif mirroring a prior observation where Hyl was mapped to the CH1-VH Fab domain interface of IgGs. In contrast to the preceding report, our structural modeling analysis on TCB mAbs unveiled substantial differences in the orientation and flexibility of motifs in immediate proximity and across the artificial CH1-VL cross Fab interface and upstream elbow segment. Utilizing a hybrid database search, RNAseq, and a CRISPR/Cas9 knockout methodology in Chinese hamster ovary (CHO) production cell lines, procollagen-lysine, 2-oxoglutarate 5-dioxygenases (PLODs) were conclusively identified as the catalyzing enzymes accountable for the 5R-Hyl modification in TCB mAbs. To quantitatively inhibit Hyl formation in TCB mAbs, the activity of all three Chinese hamster PLOD isoenzymes needs to be depleted via CRISPR/Cas9 gene knockout. Moreover, our investigation identified cell culture iron availability, process duration, and clonal variability in CHO cells as elements influencing the levels of Hyl formation in TCB mAbs. This research offers a solution for circumventing Hyl formation in therapeutic complex mAb formats, such as TCB mAbs, produced in CHO cell culture processes, thereby addressing potential technical and biological challenges associated with unintended Hyl modification.

Recombinant lactate-assimilating cyanobacteria reduce high-concentration culture-associated cytotoxicity in mammalian cells

In the fields of cultured meat, biopharmaceuticals, cell therapy, and tissue engineering, large numbers of mammalian cells are required; thus, highly-concentrated cell cultures are widely adopted. In general, such cultures can lead to cell damage caused by waste product accumulation and nutritional inadequacy. In this study, a novel co-culture system where the recombinant lactate-assimilating cyanobacterial strain, KC0110, derived from euryhaline Picosynechococcus sp. PCC 7002, and mammalian muscle cells cultured across porous membranes been developed. By using the KC0110 strain, the amount of ammonium and lactate excreted from C2C12 mouse muscle cells into the culture significantly decreased. Importantly, pyruvate and some amino acids, including pyruvate-derived amino acids, also increased significantly compared to those in monoculture of C2C12 cells. It is believed that the organic acids secreted by the KC0110 strain enhance the growth of mammalian cells, leading to a reduction in high-concentration culture-induced mammalian cell damage [lactate dehydrogenase (LDH) release] through cyanobacterial co-culture. These results show that, through co-cultivation with cyanobacteria, it is possible to culture mammalian cells, alleviating cell damage, even in highly-concentrated cultures. This study demonstrated an in vitro "symbiotic circular system" that can interchange metabolites produced by phototrophs and mammalian cells.

Disentangling the Web: An Interdisciplinary Review on the Potential and Feasibility of Spider Silk Bioproduction

The remarkable material properties of spider silk, such as its high toughness and tensile strength combined with its low density, make it a highly sought-after material with myriad applications. In addition, the biological nature of spider silk makes it a promising, potentially sustainable alternative to many toxic or petrochemical-derived materials. Therefore, interest in the heterologous production of spider silk proteins has greatly increased over the past few decades, making recombinant spider silk an important frontier in biomanufacturing. This has resulted in a diversity of potential host organisms, a large space for sequence design, and a variety of downstream processing techniques and product applications for spider silk production. Here, we highlight advances in each of these technical aspects as well as white spaces therein, still ripe for further investigation and discovery. Additionally, industry landscaping, patent analyses, and interviews with Key Opinion Leaders help define both the research and industry landscapes. In particular, we found that though textiles dominated the early products proposed by companies, the versatile nature of spider silk has opened up possibilities in other industries, such as high-performance materials in automotive applications or biomedical therapies. While continuing enthusiasm has imbued scientists and investors alike, many technical and business considerations still remain unsolved before spider silk can be democratized as a high-performance product. We provide insights and strategies for overcoming these initial hurdles, and we highlight the importance of collaboration between academia, industry, and policy makers. Linking technical considerations to business and market entry strategies highlights the importance of a holistic approach for the effective scale-up and commercial viability of spider silk bioproduction.

Engineering strategies for apoptotic bodies

Extracellular vesicles (EVs) are lipid bilayer vesicles containing proteins, lipids, nucleic acids, and metabolites secreted by cells under various physiological and pathological conditions that mediate intercellular communication. The main types of EVs include exosomes, microvesicles, and apoptotic bodies (ABs). ABs are vesicles released during the terminal stages of cellular apoptosis, enriched with diverse biological entities and characterized by distinct morphological features. As a result, ABs possess great potential in fields like disease diagnosis, immunotherapy, regenerative therapy, and drug delivery due to their specificity, targeting capacity, and biocompatibility. However, their therapeutic efficacy is notably heterogeneous, and an overdose can lead to side effects such as accumulation in the liver, spleen, lungs, and gastrointestinal system. Through bioengineering, the properties of ABs can be optimized to enhance drug-loading efficiency, targeting precision, and multifunctionality for clinical implementations. This review focuses on strategies such as transfection, sonication, electroporation, surface engineering, and integration with biomaterials to enable ABs to load cargoes and enhance targeting, providing insights into the engineering of ABs.

Multiplex genome editing eliminates the Warburg Effect without impacting growth rate in mammalian cells

The Warburg effect is ubiquitous in proliferative mammalian cells, including cancer cells, but poses challenges for biopharmaceutical production, as lactate accumulation inhibits cell growth and protein production. Previous efforts to eliminate lactate production via knockout have failed in mammalian bioprocessing since lactate dehydrogenase has proven essential. However, here we eliminated the Warburg effect in Chinese hamster ovary (CHO) and HEK293 cells by simultaneously knocking out lactate dehydrogenase and regulators involved in a negative feedback loop that typically inhibits pyruvate conversion to acetyl-CoA. In contrast to long-standing assumptions about the role of aerobic glycolysis, Warburg-null cells maintain wildtype growth rate while producing negligible lactate. Further characterization of Warburg-null CHO cells showed a compensatory increase in oxygen consumption, a near total reliance on oxidative metabolism, and higher cell densities in fed-batch cell culture. These cells remained amenable for production of diverse biotherapeutic proteins, reaching industrially relevant titers and maintaining product glycosylation. Thus, the ability to eliminate the Warburg effect is an important development for biotherapeutic production and provides a tool for investigating a near-universal metabolic phenomenon.

The United States Food and Drug Administration's Platform Technology Designation to Expedite the Development of Drugs

Drug development costs can be significantly reduced if proven "platform" technologies are allowed to be used without having to validate their use. The most recent US Food and Drug Administration (FDA) guideline brings more clarity, as well as a greater focus on the most complex technologies that can now be used for faster drug development. The FDA has highlights the use of lipid nanoparticles (LNPs) to package and deliver mRNA vaccines, gene therapy, and short (2-20 length) synthetic nucleotides (siRNA). Additionally, monoclonal antibody cell development is targeted. The FDA provides a systematic process of requesting platform status to benefit from its advantages. It brings advanced science and rationality into regulatory steps for the FDA's approval of drugs and biologicals.

Conjugated Nonionic Detergent Micelles: An Efficient Purification Platform for Dimeric Human Immunoglobulin A

The SARS-COV-2 virus is a deadly agent of inflammatory respiratory disease. Since 2020, studies have focused on developing new therapies based on galactose-rich IgA antibodies. Clinical surveys have also revealed that galactose-deficient IgA1 polymerizes in serum, producing IgA nephropathy, which is a common cause of kidney failure in young adults. Here we show that IgA1-IgA2 dimers are efficiently and economically purified in solution via conjugated nonionic surfactant micellar aggregates. Quantitative capture at pH 7 and extraction at pH 6.5 can avoid antibody exposure to acidic, potentially denaturing conditions. Brij-O20 aggregates lead to the highest process yields (88-91%) and purity (94%). Recovered IgA dimers preserve their native secondary structure and do not self-associate. Increasing the reaction volume has little impact on yield or purity. By introducing an efficient, inexpensive IgA purification protocol, we assist pharmaceutical firms and research laboratories in developing new IgA-based therapies as well as in increasing our understanding of IgA1 polymerization.

Time-resolved fluoroimmunoassay for Aspergillus detection based on anti-galactomannan monoclonal antibody from stable cell line

Invasive Aspergillosis is a high-risk illness with a high death rate in immunocompromised people due to a lack of early detection and timely treatment. Based on immunology study, we achieved an efficient production of anti-galactomannan antibody by Chinese hamster ovary (CHO) cells and applied it to time-resolved fluoroimmunoassay for Aspergillus galactomannan detection. We first introduced dual promoter expression vector into CHO host cells, and then applied a two-step screening strategy to screen the stable cell line by methionine sulfoximine pressurization. After amplification and fermentation, antibody yield reached 4500 mg/L. Then we conjugated the antibodies with fluorescent microspheres to establish a double antibody sandwich time-resolved fluoroimmunoassay, which was compared with the commercial Platelia™ Aspergillus Ag by clinical serum samples. The preformed assay could obtain the results in less than 25 min, with a limit of detection for galactomannan of approximately 1 ng/mL. Clinical results of the two methods showed that the overall percent agreement was 97.7% (95% CI: 96.6%-98.4%) and Cohen's kappa coefficient was 0.94. Overall, the assay is highly consistent with commercial detection, providing a more sensitive and effective method for the rapid diagnosis of invasive aspergillosis.

Microfluidic Mechanoporation: Current Progress and Applications in Stem Cells

Intracellular delivery, the process of transporting substances into cells, is crucial for various applications, such as drug delivery, gene therapy, cell imaging, and regenerative medicine. Among the different approaches of intracellular delivery, mechanoporation stands out by utilizing mechanical forces to create temporary pores on cell membranes, enabling the entry of substances into cells. This method is promising due to its minimal contamination and is especially vital for stem cells intended for clinical therapy. In this review, we explore various mechanoporation technologies, including microinjection, micro-nano needle arrays, cell squeezing through physical confinement, and cell squeezing using hydrodynamic forces. Additionally, we highlight recent research efforts utilizing mechanoporation for stem cell studies. Furthermore, we discuss the integration of mechanoporation techniques into microfluidic platforms for high-throughput intracellular delivery with enhanced transfection efficiency. This advancement holds potential in addressing the challenge of low transfection efficiency, benefiting both basic research and clinical applications of stem cells. Ultimately, the combination of microfluidics and mechanoporation presents new opportunities for creating comprehensive systems for stem cell processing.

Nature as blueprint: Global phenotype engineering of CHO production cells based on a multi-omics comparison with plasma cells

Especially for the production of artificial, difficult to express molecules a further development of the CHO production cell line is required to keep pace with the continuously increasing demands. However, the identification of novel targets for cell line engineering to improve CHO cells is a time and cost intensive process. Since plasma cells are evolutionary optimized for a high antibody expression in mammals, we performed a comprehensive multi-omics comparison between CHO and plasma cells to exploit optimized cellular production traits. Comparing the transcriptome, proteome, miRNome, surfaceome and secretome of both cell lines identified key differences including 392 potential overexpression targets for CHO cell engineering categorized in 15 functional classes like transcription factors, protein processing or secretory pathway. In addition, 3 protein classes including 209 potential knock-down/out targets for CHO engineering were determined likely to affect aggregation or proteolysis. For production phenotype engineering, several of these novel targets were successfully applied to transient and transposase mediated overexpression or knock-down strategies to efficiently improve productivity of CHO cells. Thus, substantial improvement of CHO productivity was achieved by taking nature as a blueprint for cell line engineering.

Reprogramming anchorage dependency to develop cell lines for recombinant protein expression

As the biopharmaceutical industry continues to mature in its cost-effectiveness and productivity, many companies have begun employing larger-scale biomanufacturing and bioprocessing protocols. While many of these protocols require cells with anchorage-independent growth, it remains challenging to induce the necessary suspension adaptations in many different cell types. In addition, although transfection efficiency is an important consideration for all cells, especially for therapeutic protein production, cells in suspension are generally more difficult to transfect than adherent cells. Thus, much of the biomanufacturing industry is focused on the development of new human cell lines with properties that can support more efficient biopharmaceutical production. With this in mind, we identified a set of "Adherent-to-Suspension Transition" (AST) factors, IKZF1, BTG2 and KLF1, the expression of which induces adherent cells to acquire anchorage-independent growth. Working from the HEK293A cell line, we established 293-AST cells and 293-AST-TetR cells for inducible and reversible reprogramming of anchorage dependency. Surprisingly, we found that the AST-TetR system induces the necessary suspension adaptations with an accompanying increase in transfection efficiency and protein expression rate. Our AST-TetR system therefore represents a novel technological platform for the development of cell lines used for generating therapeutic proteins.

Simplifying stable CHO cell line generation with high probability of monoclonality by using microfluidic dispensing as an alternative to fluorescence activated cell sorting

Single cell cloning is a critical step for cell line development (CLD) for therapeutic protein production, with proof of monoclonality being compulsorily sought in regulatory filings. Among the different single cell deposition technologies, we found that fluorescence activated cell sorting (FACS) offers high probability of monoclonality and can allow selective enrichment of the producer cells. However, FACS instruments are expensive and resource-intensive, have a large footprint, require highly skilled operators and take hours for setup, thereby complicating the cell line generation process. With the aim of finding an easy-to-use alternative to FACS, we identified a flow cytometry-based microfluidic cell dispenser, which presents a single cell sorting solution for biopharmaceutical CLD. The microfluidic cell dispenser is small, budget-friendly, easy-to-use, requires lower-cost consumables, permits flow cytometry-enabled multiparametric target cell enrichment and offers fast and gentle single cell dispensing into multiwell plates. Following comprehensive evaluation, we found that single cell deposition by the microfluidic cell dispenser resulted in >99% probability of monoclonality for production cell lines. Moreover, the clonally derived producer cell lines generated from the microfluidic cell dispenser demonstrated comparable or improved growth profiles and production capability compared to the FACS derived cell lines. Taken together, microfluidic cell dispensing can serve as a cost-effective, efficient and convenient alternative to FACS, simplifying the biopharmaceutical CLD platform with significant reductions in both scientist time and running costs.

Demonstration of a robust high cell density transient CHO platform yielding mAb titers of up to 2 g/L without medium exchange

Biopharmaceuticals like therapeutic monoclonal antibodies (mAbs) and other derived proteins are popular for treating various diseases. Transient gene expression (TGE) is typically used as a fast yet efficient method to generate moderate amounts of material. It has been used to support early stage research and discovery processes. Introduction of a robust high yielding and predictive TGE platform in Chinese hamster ovary (CHO) is crucial. It maintains the consistency in cell lines and processes throughout the early drug discovery and downstream manufacturing processes. This helps researchers to identify the issues at an early stage for timely resolution. In this study, we have demonstrated a simple high-titer platform for TGE in CHO based on a dilution process of seeding cells. We achieved titers ranging from 0.8 to 1.9 g/L for eight model mAbs at three scales (1, 30, 100 mL) in 10 days using our new platform. The ability to seed by dilution significantly streamlined the process and dramatically enhanced platform throughput. We observed a modest reduction in titer ranging from 11% to 28% when cells were seeded using dilution compared to when cells were seeded using medium exchange. Further studies revealed that carry over of spent medium into transfection negatively affected the DNA uptake and transcription processes, while the translation and secretion was minimally impacted. In summary, our transient CHO platform using cells prepared by dilution at high densities can achieve high titers of up to 1.9 g/L, which can be further improved by targeting the bottlenecks of transfection and transcription.

A deep-well plate enabled automated high-throughput cell line development platform

Cell line development (CLD) plays a crucial role in the manufacturing process development of therapeutic biologics. Most biologics are produced in Chinese hamster ovary (CHO) cell. Because of the nature of random transgene integration in CHO genome and CHO's inherent plasticity, stable CHO transfectants usually have a vast diversity in productivity, growth, and product quality. Thus, we often must resort to screening a large number of cell pools and clones to increase the probability of identifying the ideal production cell line, which is a very laborious and resource-demanding process. Here we have developed a deep-well plate (DWP) enabled high throughput (DEHT) CLD platform using 24-well DWP (24DWP), liquid handler, and other automation components. This platform has capabilities covering the key steps of CLD including cell passaging, clone imaging and expansion, and fed-batch production. We are the first to demonstrate the suitability of 24DWP for CLD by confirming minimal well-to-well and plate-to-plate variability and the absence of well-to-well cross contamination. We also demonstrated that growth, production, and product quality of 24DWP cultures were comparable to those of conventional shake flask cultures. The DEHT platform enables scientists to screen five times more cultures than the conventional CLD platform, thus significantly decreases the resources needed to identify an ideal production cell line for biologics manufacturing.

Seroprevalence of the novel swine acute diarrhea syndrome coronavirus in China assessed by enzyme-linked immunosorbent assay

The endemic outbreak of SADS-CoV has resulted in economic losses and potentially threatened the safety of China's pig industry. The molecular epidemiology of SADS-CoV in pig herds has been investigated in many provinces in China. However, there are no data over a long-time span, and there is a lack of extensive serological surveys to assess the prevalence of SADS-CoV in Chinese swine herds since the discovery of SADS-CoV. In this study, an indirect anti-SADS-CoV IgG enzyme-linked immunosorbent assay (ELISA) based on the SADS-CoV S1 protein was established to investigate the seroprevalence of SADS-CoV in Chinese swine herds. Cross-reactivity assays, indirect immunofluorescence, and western blotting assays showed that the developed ELISA had excellent SADS-CoV specificity. In total, 12,978 pig serum samples from 29 provinces/municipalities/autonomous regions in China were tested from 2022 to 2023. The results showed that the general seroprevalence of SADS-CoV in China was 59.97%, with seroprevalence ranging from 16.7% to 77.12% in different provinces and from 42.61% to 68.45% in different months. SADS-CoV is widely prevalent in China, and its seroprevalence was higher in Northeast China, North China, and Central China than in other regions. Among the four seasons, the prevalence of SADS-CoV was the highest in spring and the lowest in autumn. The results of this study provide the general seroprevalence profile of SADS-CoV in China, facilitating the understanding of the prevalence of SADS-CoV in pigs. More importantly, this study is beneficial in formulating preventive and control measures for SADS-CoV and may provide directions for vaccine development.

A nanowell platform to identify, sort and expand high antibody-producing cells

Increased use of therapeutic monoclonal antibodies and the relatively high manufacturing costs fuel the need for more efficient production methods. Here we introduce a novel, fast, robust, and safe isolation platform for screening and isolating antibody-producing cell lines using a nanowell chip and an innovative single-cell isolation method. An anti-Her2 antibody producing CHO cell pool was used as a model. The platform; (1) Assures the single-cell origin of the production clone, (2) Detects the antibody production of individual cells and (3) Isolates and expands the individual cells based on their antibody production. Using the nanowell platform we demonstrated an 1.8-4.5 increase in anti-Her2 production by CHO cells that were screened and isolated with the nanowell platform compared to CHO cells that were not screened. This increase was also shown in Fed-Batch cultures where selected high production clones showed titers of 19-100 mg/L on harvest day, while the low producer cells did not show any detectable anti-Her2 IgG production. The screening of thousands of single cells is performed under sterile conditions and the individual cells were cultured in buffers and reagents without animal components. The time required from seeding a single cell and measuring the antibody production to fully expanded clones with increased Her-2 production was 4-6 weeks.

Synergistic promotion of transient transgene expression in CHO cells by PDI/XBP-1s co-transfection and mild hypothermia

Transient gene expression system is an important tool for rapid production of recombinant proteins in Chinese hamster ovary (CHO) cells. However, their low productivity is the main hurdle to overcome. An effective approach through which to obtain high protein yield involves targeting transcriptional, post-transcriptional events (PTEs), and culture conditions. Here, we investigated the effects of protein disulfide isomerase (PDI) and spliced X-box binding protein 1 (XBP-1s) co-overexpression combined with mild hypothermia on the transient yields of recombinant proteins in CHO cells. The results showed that the gene of interest (GOI) and the PDI/XBP-1s helper vector at a co-transfection ratio of 10:1 could obviously increase transient expression level of recombinant protein in CHO cells. However, PDI/XBP-1s overexpression had no significance effect on the mRNA levels of the recombinant protein, suggesting that it targeted PTEs. Moreover, the increased production was due to the enhancing of cell specific productivity, not related to cell growth, viability, and cell cycle. In addition, combined PDI/XBP-1s co-overexpression and mild hypothermia could further improve Adalimumab expression, compared to the control/37 °C and PDI/XBP-1s/37 °C, the Adalimumab volume yield of PDI/XBP-1s/33 °C increased by 203% and 142%, respectively. Mild hypothermia resulted in 3.52- and 2.33-fold increase in the relative mRNA levels of PDI and XBP-1s, respectively. In conclusion, the combination of PDI/XBP-1s overexpression and culture temperature optimization can achieve higher transient expression of recombinant protein, which provides a synergetic strategy to improve transient production of recombinant protein in CHO cells.

Development of a [89Zr]Zr-labeled Human Antibody using a Novel Phage-displayed Human scFv Library

PURPOSE

Tax-interacting protein 1 (TIP1) is a cancer-specific radiation-inducible cell surface antigen that plays a role in cancer progression and resistance to therapy. This study aimed to develop a novel anti-TIP1 human antibody for noninvasive PET imaging in patients with cancer.

EXPERIMENTAL DESIGN

A phage-displayed single-chain variable fragment (scFv) library was created from healthy donors' blood. High-affinity anti-TIP1 scFvs were selected from the library and engineered to human IgG1. Purified Abs were characterized by size exclusion chromatography high-performance liquid chromatography (SEC-HPLC), native mass spectrometry (native MS), ELISA, BIAcore, and flow cytometry. The labeling of positron emitter [89Zr]Zr to the lead Ab, L111, was optimized using deferoxamine (DFO) chelator. The stability of [89Zr]Zr-DFO-L111 was assessed in human serum. Small animal PET studies were performed in lung cancer tumor models (A549 and H460).

RESULTS

We obtained 95% pure L111 by SEC-HPLC. Native MS confirmed the intact mass and glycosylation pattern of L111. Conjugation of three molar equivalents of DFO led to the optimal DFO-to-L111 ratio of 1.05. Radiochemical purity of 99.9% and specific activity of 0.37 MBq/μg was obtained for [89Zr]Zr-DFO-L111. [89Zr]Zr-DFO-L111 was stable in human serum over 7 days. The immunoreactive fraction in cell surface binding studies was 96%. In PET, preinjection with 4 mg/kg cold L111 before [89Zr]Zr-DFO-L111 (7.4 MBq; 20 μg) significantly (P < 0.01) enhanced the tumor-to-muscle standard uptake values (SUVmax) ratios on day 5 compared with day 2 postinjection.

CONCLUSIONS

L111 Ab targets lung cancer cells in vitro and in vivo. [89Zr]Zr-DFO-L111 is a human antibody that will be evaluated in the first in-human study of safety and PET imaging.

Advancements in CHO metabolomics: techniques, current state and evolving methodologies

Background: Investigating the metabolic behaviour of different cellular phenotypes, i.e., good/bad grower and/or producer, in production culture is important to identify the key metabolite(s)/pathway(s) that regulate cell growth and/or recombinant protein production to improve the overall yield. Currently, LC-MS, GC-MS and NMR are the most used and advanced technologies for investigating the metabolome. Although contributed significantly in the domain, each technique has its own biasness towards specific metabolites or class of metabolites due to various reasons including variability in the concept of working, sample preparation, metabolite-extraction methods, metabolite identification tools, and databases. As a result, the application of appropriate analytical technique(s) is very critical. Purpose and scope: This review provides a state-of-the-art technological insights and overview of metabolic mechanisms involved in regulation of cell growth and/or recombinant protein production for improving yield from CHO cultures. Summary and conclusion: In this review, the advancements in CHO metabolomics over the last 10 years are traced based on a bibliometric analysis of previous publications and discussed. With the technical advancement in the domain of LC-MS, GC-MS and NMR, metabolites of glycolytic and nucleotide biosynthesis pathway (glucose, fructose, pyruvate and phenylalanine, threonine, tryptophan, arginine, valine, asparagine, and serine, etc.) were observed to be upregulated in exponential-phase thereby potentially associated with cell growth regulation, whereas metabolites/intermediates of TCA, oxidative phosphorylation (aspartate, glutamate, succinate, malate, fumarate and citrate), intracellular NAD+/NADH ratio, and glutathione metabolic pathways were observed to be upregulated in stationary-phase and hence potentially associated with increased cell-specific productivity in CHO bioprocess. Moreover, each of technique has its own bias towards metabolite identification, indicating their complementarity, along with a number of critical gaps in the CHO metabolomics pipeline and hence first time discussed here to identify their potential remedies. This knowledge may help in future study designs to improve the metabolomic coverage facilitating identification of the metabolites/pathways which might get missed otherwise and explore the full potential of metabolomics for improving the CHO bioprocess performances.

Manipulating gene expression levels in mammalian cell factories: An outline of synthetic molecular toolboxes to achieve multiplexed control

Mammalian cells have developed dedicated molecular mechanisms to tightly control expression levels of their genes where the specific transcriptomic signature across all genes eventually determines the cell's phenotype. Modulating cellular phenotypes is of major interest to study their role in disease or to reprogram cells for the manufacturing of recombinant products, such as biopharmaceuticals. Cells of mammalian origin, for example Chinese hamster ovary (CHO) and Human embryonic kidney 293 (HEK293) cells, are most commonly employed to produce therapeutic proteins. Early genetic engineering approaches to alter their phenotype have often been attempted by "uncontrolled" overexpression or knock-down/-out of specific genetic factors. Many studies in the past years, however, highlight that rationally regulating and fine-tuning the strength of overexpression or knock-down to an optimum level, can adjust phenotypic traits with much more precision than such "uncontrolled" approaches. To this end, synthetic biology tools have been generated that enable (fine-)tunable and/or inducible control of gene expression. In this review, we discuss various molecular tools used in mammalian cell lines and group them by their mode of action: transcriptional, post-transcriptional, translational and post-translational regulation. We discuss the advantages and disadvantages of using these tools for each cell regulatory layer and with respect to cell line engineering approaches. This review highlights the plethora of synthetic toolboxes that could be employed, alone or in combination, to optimize cellular systems and eventually gain enhanced control over the cellular phenotype to equip mammalian cell factories with the tools required for efficient production of emerging, more difficult-to-express biologics formats.

Improving product quality and productivity of an antibody-based biotherapeutic using inverted frustoconical shaking bioreactors

The Chinese hamster ovarian (CHO) cells serve as a common choice in biopharmaceutical production, traditionally cultivated in stirred tank bioreactors (STRs). Nevertheless, the pursuit of improved protein quality and production output for commercial purposes demand exploration into new bioreactor types. In this context, inverted frustoconical shaking bioreactors (IFSB) present unique physical properties distinct from STRs. This study aims to compare the production processes of an antibody-based biotherapeutic in both bioreactor types, to enhance production flexibility. The findings indicate that, when compared to STRs, IFSB demonstrates the capability to produce an antibody-based biotherapeutic with either comparable or enhanced bioprocess performance and product quality. IFSB reduces shear damage to cells, enhances viable cell density (VCD), and improves cell state at a 5-L scale. Consequently, this leads to increased protein expression (3.70 g/L vs 2.56 g/L) and improved protein quality, as evidenced by a reduction in acidic variants from 27.0% to 21.5%. Scaling up the culture utilizing the Froude constant and superficial gas velocity ensures stable operation, effective mixing, and gas transfer. The IFSB maintains a high VCD and cell viability at both 50-L and 500-L scales. Product expression levels range from 3.0 to 3.6 g/L, accompanied by an improved acidic variants attribute of 20.6%-22.7%. The IFSB exhibits superior productivity and product quality, underscoring its potential for incorporation into the manufacturing process for antibody-based biotherapeutics. These results establish the foundation for IFSB to become a viable option in producing antibody-based biotherapeutics for clinical and manufacturing applications.

Diverse origins of fibrinolytic enzymes: A comprehensive review

Fibrinolytic enzymes cleave fibrin which plays a crucial role in thrombus formation which otherwise leads to cardiovascular diseases. While different fibrinolytic enzymes have been purified, only a few have been utilized as clinical and therapeutic agents; hence, the search continues for a fibrinolytic enzyme with high specificity, fewer side effects, and one that can be mass-produced at a lower cost with a higher yield. In this context, this review discusses the physiological mechanism of thrombus formation and fibrinolysis, and current thrombolytic drugs in use. Additionally, an overview of the optimization, production, and purification of fibrinolytic enzymes and the role of Artificial Intelligence (AI) in optimization and the patents granted is provided. This review classifies microbial as well as non-microbial fibrinolytic enzymes isolated from food sources, including fermented foods and non-food sources, highlighting their advantages and disadvantages. Despite holding immense potential for the discovery of novel fibrinolytic enzymes, only a few fermented food sources limited to Asian countries have been studied, necessitating the research on fibrinolytic enzymes from fermented foods of other regions. This review will aid researchers in selecting optimal sources for screening fibrinolytic enzymes and is the first one to provide insights and draw a link between the implication of source selection and in vivo application.

A Step-by-Step Guide for the Production of Recombinant Fluorescent TAT-HA-Tagged Proteins and their Transduction into Mammalian Cells

Investigating the function of target proteins for functional prospection or therapeutic applications typically requires the production and purification of recombinant proteins. The fusion of these proteins with tag peptides and fluorescently derived proteins allows the monitoring of candidate proteins using SDS-PAGE coupled with western blotting and fluorescent microscopy, respectively. However, protein engineering poses a significant challenge for many researchers. In this protocol, we describe step-by-step the engineering of a recombinant protein with various tags: TAT-HA (trans-activator of transduction-hemagglutinin), 6×His and EGFP (enhanced green fluorescent protein) or mCherry. Fusion proteins are produced in E. coli BL21(DE3) cells and purified by immobilized metal affinity chromatography (IMAC) using a Ni-nitrilotriacetic acid (NTA) column. Then, tagged recombinant proteins are introduced into cultured animal cells by using the penetrating peptide TAT-HA. Here, we present a thorough protocol providing a detailed guide encompassing every critical step from plasmid DNA molecular assembly to protein expression and subsequent purification and outlines the conditions necessary for protein transduction technology into animal cells in a comprehensive manner. We believe that this protocol will be a valuable resource for researchers seeking an exhaustive, step-by-step guide for the successful production and purification of recombinant proteins and their entry by transduction within living cells. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: DNA cloning, molecular assembly strategies, and protein production Basic Protocol 2: Protein purification Basic Protocol 3: Protein transduction in mammalian cells.

Goat mammary epithelial cells provide a better expression system for production of recombinant human bone morphogenetic protein 2 compared to Chinese hamster ovarian cells

Bone Morphogenetic Protein 2 (BMP2), a member of the Transforming Growth Factor-β (TGF-β) super family of proteins and is instrumental in the repair of fractures. The synthesis of BMP2 involves extensive post-translational processing and several studies have demonstrated the abysmally low production of rhBMP2 in eukaryotic systems, which may be due to the short half-life of the bioactive protein. Consequently, production costs of rhBMP2 are quite high, limiting its availability to the general populace. Therefore, there is an urgent need to identify better in-vitro systems for large scale production of rhBMP2. In the present study, we have carried out a comparative analysis of rhBMP2 production by the conventionally used Chinese Hamster ovarian cells (CHO) and goat mammary epithelial cells (GMEC), upon transfection with appropriate construct. Udder gland cells are highly secretory, and we reasoned that such cells may serve as a better in-vitro model for large scale production of rhBMP2. Our results indicated that the synthesis and secretion of bioactive rhBMP2 by goat mammary epithelial cells was significantly higher as compared to that by CHO-K1 cells. Our results provide strong evidence that GMECs may serve as a better alternative to other mammalian cells used for therapeutic protein production.

Intensified perfusion culture (IPC) reduced recombinant protein fragmentation

Mammalian cells remain the mainstay of biological production host. In industry, cultivating and harvest strategies are sorted in batch mode (e.g., batch, fed-batch, concentrated fed-batch and intensified fed-batch) and continuous mode (e.g., perfusion). To retrieve greater productivity and better product quality, especially for the sensitive products prone to fragmentation, culture modes with various modifications are innovated (e.g., intensified perfusion culture [IPC]). In our study, we demonstrated that the fragmentation of Fc-fusion product (Molecule A) is time-dependent in traditional fed-batch (TFB) culture. The fragmentation proportion increased from 3.8% to 12.4% for Clone A, 0.8% to 1.7% for Clone B and 0.9% to 2.0% for Clone C from Day 10 to Day 14. By applying a novel bioprocess, IPC, which allows continuous feeding of the fresh medium and constant removal of the spent medium without bleeding cells to maintain a defined constant viable cell density, the fragmentation was reduced to 0.3% while the productivity was increased from 2.96 g/L to 15.51 g/L for Clone A. To validate whether the fragmentation reduction is product-sensitive, plasmids carrying the DNA sequences of two other Fc-fusion molecules (Molecule B and Molecule C) were transfected into the host. The results showed consistent fragmentation reducing effect by using IPC. Furthermore, the cultivation scale was expanded to 50 L and 1000 L. A minimum fragmentation level below 0.1% was observed for Molecule C. Our study revealed the capability of IPC in reducing Fc-fusion protein fragmentation and the reproducibility when scaling up while maintaining high productivity.

Genome-wide CRISPR/Cas9 knockout screening to mitigate cell growth inhibition induced by histone deacetylase inhibitors in recombinant CHO cells

Histone deacetylase inhibitors (iHDACs) have been extensively studied as enhancers of therapeutic protein production in recombinant Chinese hamster ovary (CHO) (rCHO) cell cultures. However, the addition of iHDACs reduces the viable cell concentration (VCC) in rCHO cell cultures, thereby reducing their potential to enhance therapeutic protein production. To mitigate the negative effects of iHDACs on VCC, screening using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-based single-gene knockout (KO) library in rCHO cells was performed in the presence of CI994, a member of iHDACs, and 10 potential KO genes that enhanced the VCC of CI994-treated rCHO cells were identified. Among these, Bcor was validated as a promising KO target that improved VCC without negatively affecting the specific productivity in the presence of CI994. Bcor KO increased the VCC and therapeutic protein concentrations in both batch and fed-batch cultures in the presence of CI994. Taken together, these findings highlight the potential of the whole-genome CRISPR/Cas9-based single-gene KO cell library to identify KO target genes for the development of iHDAC-resistant rCHO cells for enhanced therapeutic protein production.

Development of a novel tyrosine-based selection system for generation of recombinant Chinese hamster ovary cells

Efficiently expanding Chinese hamster ovary (CHO) cells, which serve as the primary host cells for recombinant protein production, have gained increasing industrial significance. A significant hurdle in stable cell line development is the low efficiency of the target gene integrated into the host genome, implying the necessity for an effective screening and selection procedure to separate these stable cells. In this study, the genes of phenylalanine hydroxylase (PAH) and pterin 4 alpha carbinolamine dehydratase 1 (PCBD1), which are key enzymes in the tyrosine synthesis pathway, were utilized as selection markers and transduced into host cells together with the target genes. This research investigated the enrichment effect of this system and advanced further in understanding its benefits for cell line development and rCHO cell culture. A novel tyrosine-based selection system that only used PCBD1 as a selection marker was designed to promote the enrichment effect. Post 9 days of starvation, positive transductants in the cell pool approached 100%. Applied the novel tyrosine-based selection system, rCHO cells expressing E2 protein were generated and named CHO TS cells. It could continue to grow, and the yield of E2 achieved 95.95 mg/L in a tyrosine-free and chemically-defined (CD) medium. Herein, we introduced an alternative to antibiotic-based selections for the establishment of CHO cell lines and provided useful insights for the design and development of CD medium.

From Efficiency to Yield: Exploring Recent Advances in CHO Cell Line Development for Monoclonal Antibodies

The increasing demand for biosimilar monoclonal antibodies (mAbs) has prompted the development of stable high-producing cell lines while simultaneously decreasing the time required for screening. Existing platforms have proven inefficient, resulting in inconsistencies in yields, growth characteristics, and quality features in the final mAb products. Selecting a suitable expression host, designing an effective gene expression system, developing a streamlined cell line generation approach, optimizing culture conditions, and defining scaling-up and purification strategies are all critical steps in the production of recombinant proteins, particularly monoclonal antibodies, in mammalian cells. As a result, an active area of study is dedicated to expression and optimizing recombinant protein production. This review explores recent breakthroughs and approaches targeted at accelerating cell line development to attain efficiency and consistency in the synthesis of therapeutic proteins, specifically monoclonal antibodies. The primary goal is to bridge the gap between rising demand and consistent, high-quality mAb production, thereby benefiting the healthcare and pharmaceutical industries.

Development of Noninvasive Activity-Based Protein Profiling-Bioluminescence Resonance Energy Transfer Platform Technology Enables Target Engagement Studies with Absolute Specificity in Living Systems

Noninvasive, real-time, longitudinal imaging of protein functions in living systems with unprecedented specificity is one of the critical challenges of modern biomedical research. Toward that goal, here, we report a platform fusion technology called activity-based protein profiling-bioluminescence resonance energy transfer (ABPP-BRET). This method provides an opportunity to study the post-translational modification of a target protein in real time in living systems in a longitudinal manner. This semisynthetic BRET biosensor method is used for target engagement studies and further for inhibitor profiling in live cells. The simplicity of this method coupled with the critical physical distance-dependent BRET readout turned out to be a powerful method, thus pushing the activity-based protein profiling technology to the next level.

Elucidating the effects of microbubble pinch-off dynamics on mammalian cell viability

In the biotechnology industry, ensuring the health and viability of mammalian cells, especially Chinese Hamster Ovary (CHO) cells, plays a significant role in the successful production of therapeutic agents. These cells are typically cultivated in aerated bioreactors, where they encounter fluid stressors from rapidly deforming bubbles. These stressors can disrupt essential biological processes and potentially lead to cell death. However, the impact of these transient, elevated stressors on cell viability remains elusive. In this study, we first employ /cgqamicrofluidics to expose CHO cells near to bubbles undergoing pinch-off, subsequently collecting and assaying the cells to quantify the reduction in viability. Observing a significant impact, we set out to understand this phenomenon. We leverage computational fluid dynamics and numerical particle tracking to map the stressor field history surrounding a rapidly deforming bubble. Separately, we expose CHO cells to a known stressor level in a flow constriction device, collecting and assaying the cells to quantify the reduction in viability. By integrating the numerical data and results from the flow constriction device experiments, we develop a predictive model for cell viability reduction. We validate this model by comparing its predictions to the earlier microfluidic results, observing good agreement. Our findings provide critical insights into the relationship between bubble-induced fluid stressors and mammalian cell viability, with implications for bioreactor design and cell culture protocol optimization in the biotechnology sector.

High-level production and purification of bioactive recombinant human activin A in Chinese hamster ovary cells

Activin A, a member of the TGF-β superfamily, is a homodimer of the inhibin βΑ subunit that plays a diversity of roles in biological processes. Because of its multiple functions, significant efforts have been made to produce activin A, however, unsatisfactory results were obtained due to its low level of expression. In this study, a stable CHO cell line exhibiting high expression of rhActivin A was isolated and production of rhActivin A was achieved using the cell line from 11-day fed-batch cultures in a 7.5 L bioreactor. The production rate was 0.22 g/L, substantially higher than those reported in previous studies. The culture supernatant of the bioreactor was used to purify rhActivin A (purity: >99%, recovery rate: 47%). The purified rhActivin A exhibited biological activity, with an EC50 of 3.893 ng/mL and a specific activity of 1.38 × 103 IU/mg. The control of process-related impurities in the purified rhActivin A was successful and met the USP recommendations for use in cell therapy. Thus, our production and purification methods were appropriate for large-scale GMP-grade rhActivin A production, which can be used for various purposes including cell therapy.

Stem cell-based ischemic stroke therapy: Novel modifications and clinical challenges

Ischemic stroke (IS) causes severe disability and high mortality worldwide. Stem cell (SC) therapy exhibits unique therapeutic potential for IS that differs from current treatments. SC's cell homing, differentiation and paracrine abilities give hope for neuroprotection. Recent studies on SC modification have enhanced therapeutic effects for IS, including gene transfection, nanoparticle modification, biomaterial modification and pretreatment. These methods improve survival rate, homing, neural differentiation, and paracrine abilities in ischemic areas. However, many problems must be resolved before SC therapy can be clinically applied. These issues include production quality and quantity, stability during transportation and storage, as well as usage regulations. Herein, we reviewed the brief pathogenesis of IS, the "multi-mechanism" advantages of SCs for treating IS, various SC modification methods, and SC therapy challenges. We aim to uncover the potential and overcome the challenges of using SCs for treating IS and convey innovative ideas for modifying SCs.

Recombinant CHO Cell Pool Generation Using PiggyBac Transposon System

CHO cell pools with desirable characteristics of high titer and consistent product quality are useful for rapid production of recombinant proteins. Here, we describe the generation of CHO cell pools using the piggyBac transposon system for mediating gene integration. The method describes the co-transfection of cells with the donor plasmid (coding for the gene of interest) and the helper plasmid (coding for the transposase) using polyethyleneimine (PEI). This is followed by a genetic selection for the generation of a cell pool. The resulting cell pool can be used to start a batch or fed-batch culture. Alternatively, it can be used for generation of clonal cell lines or generation of cell banks for future use.

Tuning of CHO secretional machinery improve activity of secreted therapeutic sulfatase 150-fold

Rare diseases are, despite their name, collectively common and millions of people are affected daily of conditions where treatment often is unavailable. Sulfatases are a large family of activating enzymes related to several of these diseases. Heritable genetic variations in sulfatases may lead to impaired activity and a reduced macromolecular breakdown within the lysosome, with several severe and lethal conditions as a consequence. While therapeutic options are scarce, treatment for some sulfatase deficiencies by recombinant enzyme replacement are available. The recombinant production of such sulfatases suffers greatly from both low product activity and yield, further limiting accessibility for patient groups. To mitigate the low product activity, we have investigated cellular properties through computational evaluation of cultures with varying media conditions and comparison of two CHO clones with different levels of one active sulfatase variant. Transcriptome analysis identified 18 genes in secretory pathways correlating with increased sulfatase production. Experimental validation by upregulation of a set of three key genes improved the specific enzymatic activity at varying degree up to 150-fold in another sulfatase variant, broadcasting general production benefits. We also identified a correlation between product mRNA levels and sulfatase activity that generated an increase in sulfatase activity when expressed with a weaker promoter. Furthermore, we suggest that our proposed workflow for resolving bottlenecks in cellular machineries, to be useful for improvements of cell factories for other biologics as well.

A Versatile Method for Inducible Protein Production in 293 Cells Using the PiggyBac Transposon System

The production of recombinant proteins has helped in understanding of their function and developing new therapies. However, one of the major bottlenecks for protein production is the establishment of reliable mammalian cell lines with high expression levels. In this chapter, we describe a simple and robust system that allows for the quick establishment of stable transgenic 293 cell lines with reproducible and high protein expression levels. This methodology is based on the piggyBac transposon system and enables the inducible production of the protein of interest. Finally, this methodology can easily be used in conventional laboratory cell culture settings without requiring specialized devices.

Proliferation of mammalian cells with Chlorococcum littorale algal compounds without serum support

In recent years, serum-free medium for mammalian cell cultivation has attracted a lot of attention, considering the high cost of production and environmental load involved in developing the conventional animal sera. The use of alternative growth-promoting products in mammalian cell cultivation such as extracts from microalgae has proven to be quite beneficial and environmental-friendly. This research aims to cultivate mammalian cells with growth-promoting factors derived from Chlorococcum littorale. We have established a simple extraction using the ultrasonication method and applied the extract in place of serum on mammalian C2C12 cell lines, 3T3 cell lines, and CHO cell lines to compare and analyze the effectiveness of the extract. Cell passage was conducted in a suspended culture condition with the addition of the extract. The results indicate that the extract from microalgae shows a high proliferation rate in all cell lines without fetal bovine serum. Moreover, it is eco-friendly and has huge potential to replace the traditional cell culture system. It could be applied in the fields of regenerative medicine, gene/cell therapies, as well as cultured meat production.

Utilizing targeted integration CHO pools to potentially accelerate the GMP manufacturing of monoclonal and bispecific antibodies

Monoclonal antibodies (mAbs) are effective therapeutic agents against many acute infectious diseases including COVID-19, Ebola, RSV, Clostridium difficile, and Anthrax. mAbs can therefore help combat a future pandemic. Unfortunately, mAb development typically takes years, limiting its potential to save lives during a pandemic. Therefore "pandemic mAb" timelines need to be shortened. One acceleration tool is "deferred cloning" and leverages new Chinese hamster ovary (CHO) technology based on targeted gene integration (TI). CHO pools, instead of CHO clones, can be used for Phase I/II clinical material production. A final CHO clone (producing the mAb with a similar product quality profile and preferably with a higher titer) can then be used for Phase III trials and commercial manufacturing. This substitution reduces timelines by ~3 months. We evaluated our novel CHO TI platform to enable deferred cloning. We created four unique CHO pools expressing three unique mAbs (mAb1, mAb2, and mAb3), and a bispecific mAb (BsAb1). We then performed single-cell cloning for mAb1 and mAb2, identifying three high-expressing clones from each pool. CHO pools and clones were inoculated side-by-side in ambr15 bioreactors. CHO pools yielded mAb titers as high as 10.4 g/L (mAb3) and 7.1 g/L (BsAb1). Subcloning yielded CHO clones expressing higher titers relative to the CHO pools while yielding similar product quality profiles. Finally, we showed that CHO TI pools were stable by performing a 3-month cell aging study. In summary, our CHO TI platform can increase the speed to clinic for a future "pandemic mAb."