Efficient mAb production in CHO cells with optimized signal peptide, codon, and UTR

Inefficacy of anti-VEGF therapy reflected in VEGF-mediated photoreceptor degeneration

Retinal neovascularization (RNV) is primarily driven by vascular endothelial growth factor (VEGF). However, current anti-VEGF therapies are limited by short half-lives and repeated injections, which reduce patient quality of life and increase medical risks. Additionally, not all patients benefit from anti-VEGF monotherapy, and some problems, such as unsatisfactory vision recovery, persist after long-term treatment. In this study, we constructed a recombinant adeno-associated virus (AAV), AAV2-SPLTH, which encodes an anti-VEGF antibody similar to bevacizumab, and assessed its effects in a doxycycline-induced Tet-opsin-VEGFA mouse model of RNV. AAV2-SPLTH effectively inhibited retinal leakage, RNV progression, and photoreceptor apoptosis in a Tet-opsin-VEGF mouse model. However, proteomic sequencing showed that AAV2-SPLTH failed to rescue the expression of phototransduction-related genes, which corresponded to reduced photoreceptor cell numbers. This study suggests that anti-VEGF monotherapy can significantly inhibit RNV to some extent but may not be enough to save visual function in the long term.

IFN-α armed gE elicits superior immunogenicity compared to unmodified antigens and flagellin armed gE in mice

Herpes zoster (HZ) induces significant pain and discomfort, which can seriously affect the quality of life of patients. At present, there is no specific treatment for HZ, and the mosteffective HZ control is vaccination. The main obstacle to developing an effective HZ vaccine is poorly induced cellular immune response. In this study, the IFN-α-gE-Fc fusion protein induced higher levels of humoral and cellular immunity compared to the unengineered gE antigen and higher levels of cellular immunity compared to the flagellin-gE-Fc fusion protein in a murine model. Compared with the marketed recombinant herpes zoster vaccine (Shingrix), IFN-α-gE-Fc can replace current used MPL adjuvant. At the same time, the immunogenicity of the IFN-α-gE-Fc + AQ was not weaker than that of the marketed recombinant zoster vaccine. The novel fusion protein provides a candidate entity for the development of a safe and effective novel HZ vaccine.

A glycoengineered therapeutic anti-HBV antibody that allows increased HBsAg immunoclearance improves HBV suppression in vivo

Introduction: The effective and persistent suppression of hepatitis B surface antigen (HBsAg) in patients with chronic HBV infection (CHB) is considered to be a promising approach to achieve a functional cure of hepatitis B. In our previous study, we found that the antibody E6F6 can clear HBsAg through FcγR-mediated phagocytosis, and its humanized form (huE6F6 antibody) is expected to be a new tool for the treatment of CHB. Previous studies have shown that the glycosylation of Fc segments affects the binding of antibodies to FcγR and thus affects the biological activity of antibodies in vivo. Methods: To further improve the therapeutic potential of huE6F6, in this study, we defucosylated huE6F6 (huE6F6-fuc-), preliminarily explored the developability of this molecule, and studied the therapeutic potential of this molecule and its underlying mechanism in vitro and in vivo models. Results: huE6F6-fuc- has desirable physicochemical properties. Compared with huE6F6-wt, huE6F6-fuc- administration resulted in a stronger viral clearance in vivo. Meanwhile, huE6F6-fuc- keep a similar neutralization activity and binding activity to huE6F6-wt in vitro. Immunological analyses suggested that huE6F6-fuc- exhibited enhanced binding to hCD32b and hCD16b, which mainly contributed to its enhanced therapeutic activity in vivo. Conclusions: In summary, the huE6F6-fuc- molecule that was developed in this study, which has desirable developability, can clear HBsAg more efficiently in vivo, providing a promising treatment for CHB patients. Our study provides new guidance for antibody engineering in other disease fields.

Identification of a New Integration Site and Study on Site-Specific Integration in CHO-K1 Cells

Site-specific integration is an important approach used to address the problem of unstable cell lines in industry. In this study, we observed a reduction in the gene copy number and antibody production in a CHOK1 cell line BA03 capable of high antibody expression. We identified a new integration site named locus 7 in the intron region of the parva gene through sequencing, FISH, and genome walking. We demonstrate that the integration of the exogenous gene at this locus does not affect the transcription of the parva and, therefore, has a minimal impact on cell growth. We designed sgRNA and donor vectors to integrate the etanercept-coding gene into locus 7 and obtained a cell line, SSI-4. We performed a passaged stability study on SSI-4 and proved the possibility of the stable, site-specific integration of exogenous genes at this locus in terms of integration site, copy number, expression level, and cell growth. In summary, our study has identified a new integration site suitable for site-specific integration, which lays the foundation for the subsequent development of site-specific integration cell lines.

Comparison of different transient gene expression systems for the production of a new humanized anti-HER2 monoclonal antibody (Hersintuzumab)

BACKGROUND

Producing therapeutic proteins can be done quickly and on a large scale through Transient Gene Expression (TGE). Chinese hamster ovary (CHO) cell lines are commonly used to achieve this. Although there are few comparative studies, TGE has been observed in suspension-adapted CHO cells.

OBJECTIVES

We tested TGE's effectiveness in DG-44, CHO-S, and ExpiCHO-S cell lines with four transfection reagents.

METHODS

A design of experiments (DoE) was followed to optimize transfection using a recombinant monoclonal antibody (mAb) construct. To evaluate the efficacy, flow cytometry and ELISA were used. Feeding strategies and temperature shifts were implemented to enhance transfection effectiveness. The quality of the mAb was assessed through ELISA, SDS-PAGE, and proliferation inhibition assays.

RESULTS

We adapted all cell lines to grow in suspension using a serum-free medium. Our findings from flow cytometry and ELISA tests indicate that PEI and Pmax reagents had a higher rate of transfection and mAb production than the ExpiCHO commercial transfection reagent. While DG-44 cells had better transfection efficiency than CHO-S and ExpiCHO-S, there was no significant difference between CHO-S and ExpiCHO-S. Our TGE system was more productive at 32 °C than at 37 °C. In the optimized TGE of Pmax-based transfection in DG-44 at 37 and 32 °C, the production level of mAb was more than half of the amount of the commercial ExpiCHO-S expression system. Still, the number of transfected cells was three times higher, making it more efficient. The purified mAb from all transfected cell lines had similar structural and functional properties under different conditions.

CONCLUSION

Our research shows that using Pmax and DG-44 cells in the TGE system is a cost-effective and efficient way to produce humanized monoclonal antibodies. We discovered that this method outperforms the ExpiCHO-S kit.

Streamlined in vitro screening system of synthetic signal peptides in Chinese hamster ovary cells for therapeutic protein production

Increasing the screening efficiency and maintaining the N-terminal cleavage pattern are key factors in the development of an in vitro synthetic signal peptide screening system for high therapeutic protein production in Chinese hamster ovary (CHO) cells. This study improved the in vitro screening system of synthetic signal peptides in CHO cells for therapeutic protein production by modifying the expression vector. Incorporating a leaky stop codon with IgG transmembrane and cytoplasmic domains into the expression vector improved the proportion of high producers in establishing stable CHO cell pools. The selected signal peptides from stable CHO cell pools that were generated using degenerate codon-based oligonucleotides with a conserved polar carboxy-terminal domain in the native signal peptide showed similar N-terminal cleavage patterns to the native one. In addition, replacing native signal peptide with selected synthetic signal peptides did not influence the sialylated N-linked glycan formation and biological activity of therapeutic Fc-fusion glycoprotein in CHO cells. Thus, an in vitro synthetic signal peptide screening system can be used for therapeutic Fc-fusion glycoprotein production in CHO cells with an enhanced specific protein productivity while maintaining the N-terminal cleavage pattern similar to the native one.

Cell factory engineering: Challenges and opportunities for synthetic biology applications

The production of high-quality recombinant proteins is critical to maintaining a continuous supply of biopharmaceuticals, such as therapeutic antibodies. Engineering mammalian cell factories presents a number of limitations typically associated with the proteotoxic stress induced upon aberrant accumulation of off-pathway protein folding intermediates, which eventually culminate in the induction of apoptosis. In this review, we will discuss advances in cell engineering and their applications at different hierarchical levels of control of the expression of recombinant proteins, from transcription and translational to posttranslational modifications and subcellular trafficking. We also highlight challenges and unique opportunities to apply modern synthetic biology tools to the design of programmable cell factories for improved biomanufacturing of therapeutic proteins.

Serum-free lentiviral vector production is compatible with medium-resident nuclease activity arising from adherent HEK293T host cells engineered with a nuclease-encoding transgene

At present lentiviral vector production for cell and gene therapy commonly involves transient plasmid transfection of mammalian cells cultivated in serum-containing media and addition of exogenous nuclease to reduce host cell and plasmid DNA impurities. Switching from serum-containing media to chemically-defined, serum free media, and minimising the number of process additions, are both increasingly regarded as necessary steps for simplifying and potentially automating lentiviral vector bioprocessing in future. Here we adapted human embryonic kidney 293T (HEK293T) cells to grow in serum-free media and also modified these cells with transgenes designed to encode a secreted nuclease activity. Stable transfection of HEK293T cells with transgenes encoding the Staphylococcus aureus nuclease B (NucB) open reading frame with either its native secretion signal peptide, the murine Igκ chain leader sequence or a novel viral transport fusion protein, all resulted in qualitatively detectable nuclease activity in serum-free media. Serum-free transient transfection of human embryonic kidney HEK293T cells stably harbouring the transgene for NucB with its native secretion signal produced active lentivirus in the presence of medium-resident nuclease activity. This lentivirus material was able to transduce the AGF-T immortal T cell line with a green fluorescent protein reporter payload at a level of 2.05 × 10⁵ TU/mL (±3.34 × 10⁴ TU/mL). Sufficient nuclease activity was present in 10 μL of this unconcentrated lentivirus material to degrade 1.5 μg DNA within 2 h at 37 °C, without agitation - conditions compatible with lentivirus production. These observations demonstrate that lentiviral vector production, by transient transfection, is compatible with host cells harbouring a nuclease transgene and evidencing nuclease activity in their surrounding growth media. This work provides a solid basis for future investigations, beyond the scope of this present study, in which commercial and academic groups can apply this approach to therapeutic payloads and potentially omit exogenous nuclease bioprocess additions.

Development of MVA-d34 Tetravalent Dengue Vaccine: Design and Immunogenicity

Dengue fever, an infectious disease that affects more than 100 million people every year, is a global health problem. Vaccination may be the most effective prevention strategy for the disease. However, the development of vaccines against dengue fever is complicated by the high risk of developing an antibody-dependent increase in infection. This article describes the development of an MVA-d34 vaccine against the dengue virus based on a safe and effective MVA viral vector. The DIII domains of the envelope protein (E) of the dengue virus are used as vaccine antigens, as antibodies against these domains do not cause an enhancement of infection. The use of the DIII domains of each of the four dengue virus serotypes made it possible to generate a humoral response against all four dengue virus serotypes in immunized mice. We also showed that the sera of vaccinated mice present virus-neutralizing activity against dengue serotype 2. Thus, the developed MVA-d34 vaccine is a promising candidate vaccine against dengue fever.

Development of stable HEK293T cell pools expressing CSFV E2 protein: A potential antigen expression platform

Large quantities of antigens are required since protective antigens, such as classical swine fever virus (CSFV) E2 protein, are widely used in diagnostic reagents and subunit vaccines. Compared to clonal cell lines and transient gene expression, stable cell pools provide a potential alternative platform to rapidly produce large amounts of antigens. In this work, firstly, Human embryonic kidney 293 T (HEK293T) cell pools expressing E2 protein were developed by transduction of lentiviral vectors. On the one hand, the SP7 was selected from 7 well-performing signal peptides to remarkably increase the production of E2 protein. On the other hand, it was found that high MOI could improve the expression of E2 protein by increasing gene copy numbers. Moreover, the HEK293T cell pools were evaluated for stability by passages and batch cultures, demonstrating that the cell pools were stable for at least 90 days. And then, the performance of the cell pools in batch, fed-batch, and semi-perfusion was studied. Among them, the titer of E2 protein was up to 2 g/L in semi-perfusion, which is currently the highest to the authors' knowledge. Finally, the aggregations and immunogenicity of the E2 protein were analyzed by SDS-PAGE and immunization of mice, respectively. There was no significant difference in aggregations and antibody titers of E2 protein in three culture methods. These results suggest that stable HEK293T cell pools are a promising and robust platform for rapid and efficient production of recombinant proteins.

Development of an in vitro screening system for synthetic signal peptide in mammalian cell-based protein production

Optimizing appropriate signal peptides in mammalian cell-based protein production is crucial given that most recombinant proteins produced in mammalian cells are thought to be secreted proteins. Until now, most studies on signal peptide in mammalian cells have replaced native signal peptides with well-known heterologous signal peptides and bioinformatics-based signal peptides. In the present study, we successfully established an in vitro screening system for synthetic signal peptide in CHO cells by combining a degenerate codon-based oligonucleotides library, a site-specific integration system, and a FACS-based antibody detection assay. Three new signal peptides were screened using this new screening system, confirming to have structural properties as signal peptides by the SignalP web server, a neural network-based algorithm that quantifies the signal peptide-ness of amino acid sequences. The novel signal peptides selected in this study increased Fc-fusion protein production in CHO cells by increasing specific protein productivity, whereas they did not negatively affect cell growth. Particularly, the SP-#149 clone showed the highest q_p, 0.73 ± 0.01 pg/cell/day from day 1 to day 4, representing a 1.47-fold increase over the native signal peptide in a serum-free suspension culture mode. In addition, replacing native signal peptide with the novel signal peptides did not significantly affect sialylated N-glycan formation, N-terminal cleavage pattern, and biological function of Fc-fusion protein produced in CHO cells. The overall results indicate the utility of a novel in vitro screening system for synthetic signal peptide for mammalian cell-based protein production. KEY POINTS: • An in vitro screening system for synthetic signal peptide in mammalian cells was established • This system combined a degenerate codon-based library, site-specific integration, and a FACS-based detection assay • The novel signal peptides selected in this study could increase Fc-fusion protein production in mammalian cells.

Development of a Universal Epitope-Based Influenza Vaccine and Evaluation of Its Effectiveness in Mice

Vaccination is an effective and economically viable means of protection against the influenza virus, but due to rapid viral evolution, modern seasonal vaccines are not effective enough. Next-generation vaccines are designed to provide protection against a wide range of influenza virus strains, including pandemic variants. In our work, we made an epitope-based universal vaccine, rMVA-k1-k2, against the influenza virus based on the modified vaccinia Ankara (MVA) vector and using our own algorithms to select epitopes from conserved fragments of the NP, M1 and HA proteins of influenza A and B. We show that double immunization protects mice with a 67% or greater efficiency against viral influenza pneumonia when infected with various strains of the H1N1, H2N2, H3N2 and H5N1 subtypes of influenza A. In animals, the level of protection provided by the rMVA-k1-k2 vaccine was comparable to that provided by the universal M001 and MVA-NP+M1 (Invictus) vaccines, which have shown success in clinical trials, against strains of the H1N1 and H3N2 subtypes.

Strategies and Considerations for Improving Recombinant Antibody Production and Quality in Chinese Hamster Ovary Cells

Recombinant antibodies are rapidly developing therapeutic agents; approximately 40 novel antibody molecules enter clinical trials each year, most of which are produced from Chinese hamster ovary (CHO) cells. However, one of the major bottlenecks restricting the development of antibody drugs is how to perform high-level expression and production of recombinant antibodies. The high-efficiency expression and quality of recombinant antibodies in CHO cells is determined by multiple factors. This review provides a comprehensive overview of several state-of-the-art approaches, such as optimization of gene sequence of antibody, construction and optimization of high-efficiency expression vector, using antibody expression system, transformation of host cell lines, and glycosylation modification. Finally, the authors discuss the potential of large-scale production of recombinant antibodies and development of culture processes for biopharmaceutical manufacturing in the future.

Expression of Secreted Neutrophil Gelatinase-Associated Lipocalin in 293T Cell Using the Inducible Dual-Function System

Neutrophil gelatinase-associated lipocalin (NGAL) has emerged as a promising biomarker for the early prediction of acute kidney injury (AKI). The production of recombinant NGAL is considered to be necessary for the development of a detection method. This study intended to express the recombinant NGAL protein in 293T cell under the Tet-On inducible system and human serum albumin signal sequence (HSA-SS). The transfection efficiency and protein modulation were assessed by detecting the expression of the enhanced green fluorescent protein (EGFP) and secreted NGAL protein. Both proteins were detected only in the presence of a doxycycline (Dox) inducer. Cell toxicity was not found under any conditions. Moreover, a higher level of soluble NGAL protein in the supernatant secreted by HSA-SS compared with a native signal peptide (Nat-SS) was observed. In summary, this work successfully optimized the conditions for induction of NGAL expression. This system will provide as an efficient strategy to produce other recombinant proteins secreted from a mammalian cell.

A novel strategy for engineering of a smart generation of immune ribonucleases against EGFR+ cells

The overexpression of epidermal growth factor receptor (EGFR) could result in the development of solid tumors of prostate, breast, gastric, colorectal, ovarian, and head and neck, leading to carcinoma. Antibody therapies are ideal methods to overcome malignant diseases. However, immunoribonucleases are a new generation of antibodies in which an RNase binds to a specific antibody and shows a stronger ability to terminate cancer cells. In this study, we engineered Rana pipiens RNase to bind to the scFv of human antiepidermal growth factor receptor antibody. The molecular dynamic simulations confirmed protein stability and the ability of scFv-ranpirnase (rantoxin) to bind to epidermal growth factor receptor protein. Then, the rantoxin construct was synthesized in a pCDNA 3.1 Neo vector. CHO-K1 cells were used as expression hosts and the construct was transfected. Cells were selected by antibiotic therapies using neomycin, 120 mg/ml, and the high-yield colony was screened by real-time polymerase chain reaction (PCR) methods. Then, the recombinant protein production was confirmed using the sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blot analyses. The molecular dynamic simulation (MDS) confirmed that the I467, S468, Q408, and H409 amino acids of EGFR bonded well to rantoxin. As revealed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analyses, the rantoxin production and PCR analysis showed that the T3 colony can produce rantoxin messenger RNA fourfold higher than the GAPDH gene. The immunotoxin function was assessed in A431 cancer cells and EGFR-negative HEK293 cells, and IC₅₀  values were estimated to be 22.4 ± 3 and >620.4 ± 5 nM, respectively. The results indicated that the immunotoxins produced in this study had the potential for use as anticancer drugs.

Essentially Leading Antibody Production: An Investigation of Amino Acids, Myeloma, and Natural V-Region Signal Peptides in Producing Pertuzumab and Trastuzumab Variants

Boosting the production of recombinant therapeutic antibodies is crucial in both academic and industry settings. In this work, we investigated the usage of varying signal peptides by antibody V-genes and their roles in recombinant transient production, systematically comparing myeloma and the native signal peptides of both heavy and light chains in 168 antibody permutation variants. We found that amino acids count and types (essential or non-essential) were important factors in a logistic regression equation model for predicting transient co-transfection protein production rates. Deeper analysis revealed that the culture media were often incomplete and that the supplementation of essential amino acids can improve the recombinant protein yield. While these findings are derived from transient HEK293 expression, they also provide insights to the usage of the large repertoire of antibody signal peptides, where by varying the number of specific amino acids in the signal peptides attached to the variable regions, bottlenecks in amino acid availability can be mitigated.

Expression vector cassette engineering for recombinant therapeutic production in mammalian cell systems

Human tissue plasminogen activator was the first recombinant therapy protein that successfully produced in Chinese hamster ovary cells in 1986 and approved for clinical use. Since then, more and more therapeutic proteins are being manufactured in mammalian cells, and the technologies for recombinant protein production in this expression system have developed rapidly, with the optimization of both upstream and downstream processes. One of the most promising strategies is expression vector cassette optimization based on the expression vector cassette. In this review paper, these approaches and developments are summarized, and the future strategy on the utilizing of expression cassettes for the production of recombinant therapeutic proteins in mammalian cells is discussed.

Current Advancements in Addressing Key Challenges of Therapeutic Antibody Design, Manufacture, and Formulation

Therapeutic antibody technology heavily dominates the biologics market and continues to present as a significant industrial interest in developing novel and improved antibody treatment strategies. Many noteworthy advancements in the last decades have propelled the success of antibody development; however, there are still opportunities for improvement. In considering such interest to develop antibody therapies, this review summarizes the array of challenges and considerations faced in the design, manufacture, and formulation of therapeutic antibodies, such as stability, bioavailability and immunological engagement. We discuss the advancement of technologies that address these challenges, highlighting key antibody engineered formats that have been adapted. Furthermore, we examine the implication of novel formulation technologies such as nanocarrier delivery systems for the potential to formulate for pulmonary delivery. Finally, we comprehensively discuss developments in computational approaches for the strategic design of antibodies with modulated functions.

Construction strategies for developing expression vectors for recombinant monoclonal antibody production in CHO cells

Recent years have seen the use of recombinant proteins in the treatment of different diseases. Among them, monoclonal antibodies (mAbs) are currently the fastest growing class of bio-therapeutic recombinant proteins. Chinese hamster ovary (CHO) cells are the most commonly used host cells for production of these recombinant mAbs. Expression vectors determine the expression level and quality of recombinant mAbs. Currently, few construction strategies for recombinant mAbs expression vectors in CHO cells have been developed, including monocistronic vector, multiple-promoter expression vector, and tricistronic vector mediated by internal ribosome entry site (IRES) or Furin-2A element. Among them, Furin-2A-mediated vector is an effective approach due to advantages of high "self-cleavage" efficiency, and equal expression of light and heavy chains from a single open reading frame. Here, we have reviewed the progress in development of different strategies for constructing recombinant mAb expression vectors in CHO cells and its potential advantages and disadvantages.