In Vivo Glycan Engineering via the Mannosidase I Inhibitor (Kifunensine) Improves Efficacy of Rituximab Manufactured in Nicotiana benthamiana Plants

A Robust α-l-Fucosidase from Prevotella nigrescens for Glycoengineering Therapeutic Antibodies

Eliminating the core fucose from the N-glycans of the Fc antibody segment by pathway engineering or enzymatic methods has been shown to enhance the potency of therapeutic antibodies, especially in the context of antibody-dependent cytotoxicity (ADCC). However, there is a significant challenge due to the limited defucosylation efficiency of commercially available α-l-fucosidases. In this study, we report a unique α-l-fucosidase (PnfucA) from the bacterium Prevotella nigrescens that has a low sequence identity compared with all other known α-l-fucosidases and is highly reactive toward a core disaccharide substrate with fucose α(1,3)-, α (1,4)-and α(1,6)-linked to GlcNAc, and is less reactive toward the Fuc-α(1,2)-Gal on the terminal trisaccharide of the oligosaccharide Globo H (Bb3). The kinetic properties of the enzyme, such as its Km and kcat, were determined and the optimized expression of PnfucA gave a yield exceeding 30 mg/L. The recombinant enzyme retained its full activity even after being incubated for 6 h at 37 °C. Moreover, it retained 92 and 87% of its activity after freezing and freeze-drying treatments, respectively, for over 28 days. In a representative glycoengineering of adalimumab (Humira), PnfucA showed remarkable hydrolytic efficiency in cleaving the α(1,6)-linked core fucose from FucGlcNAc on the antibody with a quantitative yield. This enabled the seamless incorporation of biantennary sialylglycans by Endo-S2 D184 M in a one-pot fashion to yield adalimumab in a homogeneous afucosylated glycoform with an improved binding affinity toward Fcγ receptor IIIa.

Exploring the Potential of Plant-Based Nanotechnology in Cancer Immunotherapy: Benefits, Limitations, and Future Perspectives

Reconceptualizing cancer immunotherapy can be improved if combined with plant production systems and nanotechnology. This review aims to contribute to the knowledge of plant use in nanomedicine and cancer immunotherapy. In the foreground, we outlined each of these approaches; nanomedicine, green synthesis, and immunotherapy. The benefits of plant-based nanoparticles in mending the immune systems were subsequently analyzed, with reference to the literature. The combining effects of biological and therapeutic properties of some phytochemicals and their derivatives, with targeted nanoparticles and selective immunotherapy, can enhance the delivery of drugs and antibodies, and induce antitumor immune responses, via activation of functions of neutrophils, lymphocyte cells, and natural killer cells, and macrophages, resulting in induced apoptosis and phagocytosis of tumor cells, which can improve designing immunotherapeutic strategies targeting cancer, with a larger spectrum compared to the current cytotoxic anticancer drugs commonly used in clinics. This study uncovers the mechanistic drivers of cancer immunoengineering in cancer therapy using plant-based nanomaterials, enhancing therapeutic benefits while minimizing toxic and side effects.

The advent of plant cells in bioreactors

Ever since agriculture started, plants have been bred to obtain better yields, better fruits, or sustainable products under uncertain biotic and abiotic conditions. However, a new way to obtain products from plant cells emerged with the development of recombinant DNA technologies. This led to the possibility of producing exogenous molecules in plants. Furthermore, plant chemodiversity has been the main source of pharmacological molecules, opening a field of plant biotechnology directed to produce high quality plant metabolites. The need for different products by the pharma, cosmetics agriculture and food industry has pushed again to develop new procedures. These include cell production in bioreactors. While plant tissue and cell culture are an established technology, beginning over a hundred years ago, plant cell cultures have shown little impact in biotechnology projects, compared to bacterial, yeasts or animal cells. In this review we address the different types of bioreactors that are currently used for plant cell production and their usage for quality biomolecule production. We make an overview of Nicotiana tabacum, Nicotiana benthamiana, Oryza sativa, Daucus carota, Vitis vinifera and Physcomitrium patens as well-established models for plant cell culture, and some species used to obtain important metabolites, with an insight into the type of bioreactor and production protocols.

Modulating antibody effector functions by Fc glycoengineering

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

Disrupting N-Glycosylation Using Type I Mannosidase Inhibitors Alters B-Cell Receptor Signaling

Kifunensine is a known inhibitor of type I α-mannosidase enzymes and has been shown to have therapeutic potential for a variety of diseases and application in the expression of high-mannose N-glycan bearing glycoproteins; however, the compound's hydrophilic nature limits its efficacy. We previously synthesized two hydrophobic acylated derivatives of kifunensine, namely, JDW-II-004 and JDW-II-010, and found that these compounds were over 75-fold more potent than kifunensine. Here we explored the effects of these compounds on different mice and human B cells, and we demonstrate that they affected the cells in a similar fashion to kifunensine, further demonstrating their functional equivalence to kifunensine in assays utilizing primary cells. Specifically, a dose-dependent increase in the formation of high-mannose N-glycans decorated glycoproteins were observed upon treatment with kifunensine, JDW-II-004, and JDW-II-010, but greater potency was observed with the acylated derivatives. Treatment with kifunensine or the acylated derivatives also resulted in impaired B-cell receptor (BCR) signaling of the primary mouse B cells; however, primary human B cells treated with kifunensine or JDW-II-004 did not affect BCR signaling, while a modest increase in BCR signaling was observed upon treatment with JDW-010. Nevertheless, these findings demonstrate that the hydrophobic acylated derivatives of kifunensine can help overcome the mass-transfer limitations of the parent compound, and they may have applications for the treatment of ERAD-related diseases or prove to be more cost-effective alternatives for the generation and production of high-mannose N-glycan bearing glycoproteins.

Impact of glycoengineering and antidrug antibodies on the anticancer activity of a plant-made lectin-Fc fusion protein

Plants are an efficient production platform for manufacturing glycoengineered monoclonal antibodies and antibody-like molecules. Avaren-Fc (AvFc) is a lectin-Fc fusion protein or lectibody produced in Nicotiana benthamiana, which selectively recognizes cancer-associated high-mannose glycans. In this study, we report the generation of a glycovariant of AvFc that is devoid of plant glycans, including the core α1,3-fucose and β1,2-xylose residues. The successful removal of these glycans was confirmed by glycan analysis using HPLC. This variant, AvFc^ΔXF , has significantly higher affinity for Fc gamma receptors and induces higher levels of luciferase expression in an antibody-dependent cell-mediated cytotoxicity (ADCC) reporter assay against B16F10 murine melanoma cells without inducing apoptosis or inhibiting proliferation. In the B16F10 flank tumour mouse model, we found that systemic administration of AvFc^ΔXF , but not an aglycosylated AvFc variant lacking affinity for Fc receptors, significantly delayed the growth of tumours, suggesting that Fc-mediated effector functions were integral. AvFc^ΔXF treatment also significantly reduced lung metastasis of B16F10 upon intravenous challenge whereas a sugar-binding-deficient mutant failed to show efficacy. Lastly, we determined the impact of antidrug antibodies (ADAs) on drug activity in vivo by pretreating animals with AvFc^ΔXF before implanting tumours. Despite a significant ADA response induced by the pretreatment, we found that the activity of AvFc^ΔXF was unaffected by the presence of these antibodies. These results demonstrate that glycoengineering is a powerful strategy to enhance AvFc's antitumor activity.

Medicinal Plants: Guests and Hosts in the Heterologous Expression of High-Value Products

Medicinal plants play an important dual role in the context of the heterologous expression of high-value pharmaceutical products. On the one hand, the classical biochemical and modern omics approaches allowed for the discovery of various genes encoding biosynthetic pathways in medicinal plants. Recombinant DNA technology enabled introducing these genes and regulatory elements into host organisms and enhancing the heterologous production of the corresponding secondary metabolites. On the other hand, the transient expression of foreign DNA in plants facilitated the production of numerous proteins of pharmaceutical importance. This review summarizes several success stories of the engineering of plant metabolic pathways in heterologous hosts. Likewise, a few examples of recombinant protein expression in plants for therapeutic purposes are also highlighted. Therefore, the importance of medicinal plants has grown immensely as sources for valuable products of low and high molecular weight. The next step ahead for bioengineering is to achieve more success stories of industrial-scale production of secondary plant metabolites in microbial systems and to fully exploit plant cell factories' commercial potential for recombinant proteins.

Evaluation of the context of downstream N- and free N-glycomic alterations induced by swainsonine in HepG2 cells

Swainsonine (SWA), a potent inhibitor of class II α-mannosidases, is present in a number of plant species worldwide and causes severe toxicosis in livestock grazing these plants. The mechanisms underlying SWA-induced animal poisoning are not fully understood. In this study, we analyzed the alterations that occur in N- and free N-glycomic upon addition of SWA to HepG2 cells to understand better SWA-induced glycomic alterations. After SWA addition, we observed the appearance of SWA-specific glycomic alterations, such as unique fucosylated hybrid-type and fucosylated M5 (M5F) N-glycans, and a remarkable increase in all classes of Gn1 FNGs. Further analysis of the context of these glycomic alterations showed that (fucosylated) hybrid type N-glycans were not the precursors of these Gn1 FNGs and vice versa. Time course analysis revealed the dynamic nature of glycomic alterations upon exposure of SWA and suggested that accumulation of free N-glycans occurred earlier than that of hybrid-type N-glycans. Hybrid-type N-glycans, of which most were uniquely core fucosylated, tended to increase slowly over time, as was observed for M5F N-glycans. Inhibition of swainsonine-induced unique fucosylation of hybrid N-glycans and M5 by coaddition of 2-fluorofucose caused significant increases in paucimannose- and fucosylated paucimannose-type N-glycans, as well as paucimannose-type free N-glycans. The results not only revealed the gross glycomic alterations in HepG2 cells induced by swainsonine, but also provide information on the global interrelationships between glycomic alterations.

Host Cell Glycocalyx Remodeling Reveals SARS-CoV-2 Spike Protein Glycomic Binding Sites

Glycans on the host cell membrane and viral proteins play critical roles in pathogenesis. Highly glycosylated epithelial cells represent the primary boundary separating embedded host tissues from pathogens within the respiratory and intestinal tracts. SARS-CoV-2, the causative agent for the COVID-19 pandemic, reaches into the respiratory tract. We found purified human milk oligosaccharides (HMOs) inhibited the viral binding on cells. Spike (S) protein receptor binding domain (RBD) binding to host cells were partly blocked by co-incubation with exogenous HMOs, most by 2-6-sialyl-lactose (6'SL), supporting the notion that HMOs can function as decoys in defense against SARS-Cov2. To investigate the effect of host cell glycocalyx on viral adherence, we metabolically modified and confirmed with glycomic methods the cell surface glycome to enrich specific N-glycan types including those containing sialic acids, fucose, mannose, and terminal galactose. Additionally, Immunofluorescence studies demonstrated that the S protein preferentially binds to terminal sialic acids with α-(2,6)-linkages. Furthermore, site-specific glycosylation of S protein RBD and its human receptor ACE2 were characterized using LC-MS/MS. We then performed molecular dynamics calculations on the interaction complex to further explore the interactive complex between ACE2 and the S protein. The results showed that hydrogen bonds mediated the interactions between ACE2 glycans and S protein with desialylated glycans forming significantly fewer hydrogen bonds. These results supported a mechanism where the virus binds initially to glycans on host cells preferring α-(2,6)-sialic acids and finds ACE2 and with the proper orientation infects the cell.

Mannans and mannan oligosaccharides (MOS) from Saccharomyces cerevisiae - A sustainable source of functional ingredients

Sustainable industry practices and circular economy concepts encourage the transformation of production waste into by-products. Saccharomyces cerevisiae is widely used in fermentation industry worldwide, generating large amounts of spent yeast which is mainly directed to animal feed or discarded as waste. Instead of becoming and environmental problem, spent yeast can be directed to the extraction of valuable compounds such as mannans and mannan oligosaccharides (MOS). This review presents a compilation of the studies up to date regarding the different chemical, enzymatic, mechanical or physical processes addressed for mannans extraction and MOS production. Additionally, the existing studies on the chemical modification of mannans aimed to improve specific characteristics are also discussed. Finally, the more relevant bioactivities and potential applications of mannans, MOS and mannose are presented, together with products on the market containing these compounds.

Glycoengineering of Therapeutic Antibodies with Small Molecule Inhibitors

Monoclonal antibodies (mAbs) are one of the cornerstones of modern medicine, across an increasing range of therapeutic areas. All therapeutic mAbs are glycoproteins, i.e., their polypeptide chain is decorated with glycans, oligosaccharides of extraordinary structural diversity. The presence, absence, and composition of these glycans can have a profound effect on the pharmacodynamic and pharmacokinetic profile of individual mAbs. Approaches for the glycoengineering of therapeutic mAbs—the manipulation and optimisation of mAb glycan structures—are therefore of great interest from a technological, therapeutic, and regulatory perspective. In this review, we provide a brief introduction to the effects of glycosylation on the biological and pharmacological functions of the five classes of immunoglobulins (IgG, IgE, IgA, IgM and IgD) that form the backbone of all current clinical and experimental mAbs, including an overview of common mAb expression systems. We review selected examples for the use of small molecule inhibitors of glycan biosynthesis for mAb glycoengineering, we discuss the potential advantages and challenges of this approach, and we outline potential future applications. The main aim of the review is to showcase the expanding chemical toolbox that is becoming available for mAb glycoengineering to the biology and biotechnology community.

Comparison of CD20 Binding Affinities of Rituximab Produced in Nicotiana benthamiana Leaves and Arabidopsis thaliana Callus

Plants are promising drug-production platforms with high economic efficiency, stability, and convenience in mass production. However, studies comparing the equivalency between the original antibodies and those produced in plants are limited. Amino acid sequences that constitute the Fab region of an antibody are diverse, and the post-transcriptional modifications that occur according to these sequences in animals and plants are also highly variable. In this study, rituximab, a blockbuster antibody drug used in the treatment of non-Hodgkin's lymphoma, was produced in Nicotiana benthamiana leaves and Arabidopsis thaliana callus, and was compared to the original rituximab produced in CHO cells. Interestingly, the epitope recognition and antigen-binding abilities of rituximab from N. benthamiana leaves were almost lost. In the case of rituximab produced in A. thaliana callus, the specific binding ability and CD20 capping activity were maintained, but the binding affinity was less than 50% of that of original rituximab from CHO cells. These results suggest that different plant species exhibit different binding affinities. Accordingly, in addition to the differences in PTMs between mammals and plants, the differences between the species must also be considered in the process of producing antibodies in plants.

Impact of Specific N-Glycan Modifications on the Use of Plant-Produced SARS-CoV-2 Antigens in Serological Assays

The receptor binding domain (RBD) of the SARS-CoV-2 spike protein plays a key role in the virus-host cell interaction, and viral infection. The RBD is a major target for neutralizing antibodies, whilst recombinant RBD is commonly used as an antigen in serological assays. Such assays are essential tools to gain control over the pandemic and detect the extent and durability of an immune response in infected or vaccinated populations. Transient expression in plants can contribute to the fast production of viral antigens, which are required by industry in high amounts. Whilst plant-produced RBDs are glycosylated, N-glycan modifications in plants differ from humans. This can give rise to the formation of carbohydrate epitopes that can be recognized by anti-carbohydrate antibodies present in human sera. For the performance of serological tests using plant-produced recombinant viral antigens, such cross-reactive carbohydrate determinants (CCDs) could result in false positives. Here, we transiently expressed an RBD variant in wild-type and glycoengineered Nicotiana benthamiana leaves and characterized the impact of different plant-specific N-glycans on RBD reactivity in serological assays. While the overall performance of the different RBD glycoforms was comparable to each other and to a human cell line produced RBD, there was a higher tendency toward false positive results with sera containing allergy-related CCD-antibodies when an RBD carrying β1,2-xylose and core α1,3-fucose was used. These rare events could be further minimized by pre-incubating sera from allergic individuals with a CCD-inhibitor. Thereby, false positive signals obtained from anti-CCD antibodies, could be reduced by 90%, on average.

Alpha-1 antitrypsin deficiency and recombinant protein sources with focus on plant sources: Updates, challenges and perspectives

Alpha-1 antitrypsin deficiency (A1ATD) is an autosomal recessive disease characterized by low plasma levels of A1AT, a serine protease inhibitor representing the most abundant circulating antiprotease normally present at plasma levels of 1-2 g/L. The dominant clinical manifestations include predispositions to early onset emphysema due to protease/antiprotease imbalance in distal lung parenchyma and liver disease largely due to unsecreted polymerized accumulations of misfolded mutant A1AT within the endoplasmic reticulum of hepatocytes. Since 1987, the only FDA licensed specific therapy for the emphysema component has been infusions of A1AT purified from pooled human plasma at the 2020 cost of up to US $200,000/year with the risk of intermittent shortages. In the past three decades various, potentially less expensive, recombinant forms of human A1AT have reached early stages of development, one of which is just reaching the stage of human clinical trials. The focus of this review is to update strategies for the treatment of the pulmonary component of A1ATD with some focus on perspectives for therapeutic production and regulatory approval of a recombinant product from plants. We review other competitive technologies for treating the lung disease manifestations of A1ATD, highlight strategies for the generation of data potentially helpful for securing FDA Investigational New Drug (IND) approval and present challenges in the selection of clinical trial strategies required for FDA licensing of a New Drug Approval (NDA) for this disease.

Effects of Kifunensine on Production and N-Glycosylation Modification of Butyrylcholinesterase in a Transgenic Rice Cell Culture Bioreactor

The production and N-glycosylation of recombinant human butyrylcholinesterase (BChE), a model highly glycosylated therapeutic protein, in a transgenic rice cell suspension culture treated with kifunensine, a strong α-mannosidase I inhibitor, was studied in a 5 L bioreactor. A media exchange was performed at day 7 of cultivation by removing spent sugar-rich medium (NB+S) and adding fresh sugar-free (NB-S) medium to induce the rice α-amylase 3D (RAmy3D) promoter to produce rice recombinant human BChE (rrBChE). Using a 1.25X-concentrated sugar-free medium together with an 80% reduced working volume during the media exchange led to a total active rrBChE production level of 79 ± 2 µg (g FW)^-1 or 7.5 ± 0.4 mg L^-1 in the presence of kifunensine, which was 1.5-times higher than our previous bioreactor runs using normal sugar-free (NB-S) media with no kifunensine treatment. Importantly, the amount of secreted active rrBChE in culture medium was enhanced in the presence of kifunensine, comprising 44% of the total active rrBChE at day 5 following induction. Coomassie-stained SDS-PAGE gel and Western blot analyses revealed different electrophoretic migration of purified rrBChE bands with and without kifunensine treatment, which was attributed to different N-glycoforms. N-Glycosylation analysis showed substantially increased oligomannose glycans (Man5/6/7/8) in rrBChE treated with kifunensine compared to controls. However, the mass-transfer limitation of kifunensine was likely the major reason for incomplete inhibition of α-mannosidase I in this bioreactor study.

From Farm to Finger Prick-A Perspective on How Plants Can Help in the Fight Against COVID-19

As a consequence of the COVID-19 pandemic crisis, farmers across the country are plowing under their fields and laying off workers. Plant biomass has been shown by the DARPA “Blue Angel” project in 2010 to be an efficient way to rapidly make vaccines and diagnostics. This technology could pivot some areas of agriculture toward biomedical products to aid in the COVID-19 pandemic response.

Heterologous expression of biologically active Mambalgin-1 peptide as a new potential anticancer, using a PVX-based viral vector in Nicotiana benthamiana

Mambalgin-1 is a peptide that acts as a potent analgesic through inhibiting acid-sensing ion channels (ASIC) in nerve cells. Research has shown that ASIC channels are involved in the proliferation and growth of cancer cells; therefore, Mambalgin-1 can be a potential anti-cancer by inhibiting these channels. In the present study, the Nicotiana benthamiana codon optimized Mambalgin-1 gene was synthesized and cloned in PVX (potato virus X) viral vector. The two cultures of Agrobacterium containing Mambalgin-1 and P19 silencing suppressor genes were co-agroinfiltrated into N. benthamiana leaves. Five days post infiltration, the production of recombinant Mambalgin-1 was determined by western blotting. For biological activity, MTT (3(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide) was analyzed for the cytotoxicity recombinant Mambalgin-1 from the transformed plants on nervous (SH-SY5Y) and breast (MCF7) cancer cells. The results showed that the plants expressing open reading frame of Mambalgin-1 showed recombinant 7.4 kDa proteins in the entire plant extract. In the MTT test, it was found that Mambalgin-1 had cytotoxic effects on SH-SY5Y cancer cells, yet no effects on MCF7 cancer cells were observed. According to the results, the expression of the biologically active recombinant Mambalgin-1 in the transformed plant leaves was confirmed and Mambalgin-1 can also have anti-cancer (inhibition of ASIC channels) potential along with its already known analgesic effect.

Glycosylation of Fcγ receptors influences their interaction with various IgG1 glycoforms

Most of therapeutic monoclonal antibodies belong to the immunoglobulin G1 (IgG1) family; they interact with the Fcγ receptors (FcγRs) at the surface of immune cells to trigger effector functions. The IgG1-Fc N-glycans impact the interaction with FcγRs and are considered a critical quality attribute. Pioneer studies on FcγR N-glycans have unveiled an additional complexity in that the N-glycan linked on the Asn-162 of FcγRIIIa was shown to be directly involved in the strong affinity for afucosylated IgG1. The last few years have thus seen the emergence of many studies investigating the complex influence of FcγRIIIa N-glycans on the interaction with IgG1 through their glycosylation sites or their glycoprofiles. In this context, we performed site-directed mutagenesis along with glycoengineering on FcγRs (FcγRI, FcγRIIa_H131/b and FcγRIIIa_V158/F158) in an effort to elucidate the impact of FcγRs N-glycans on the interaction with IgG1. Furthermore, we assessed their binding to various trastuzumab glycoforms with an enhanced surface plasmon resonance assay. The FcγRIIIa N-glycans had the highest impact on the interaction with IgG1. More specifically, the N162 glycan positively influenced the affinity (15-fold) for afucosylated IgG1 while the N45 glycan presented a negative impact (2-fold) regardless of the IgG1 glycoforms. Interestingly, only the FcγRIIIa glycoprofile had an impact on the interaction with IgG1 with a 1.5-fold affinity increase when FcγRIIIa displays high-mannose glycans. These results provide invaluable insights into the complex and strong influence of N-glycosylation upon FcγRs/IgG1 binding and are instrumental to further understand the impact of FcγRs N-glycosylation in their natural forms.

Cancer biologics made in plants

Plants are routinely utilized as efficient production platforms for the development of anti-cancer biologics leading to novel anti-cancer vaccines, immunotherapies, and drug-delivery modalities. Various biosimilar/biobetter antibodies and immunogens based on tumor-associated antigens have been produced and optimized for plant expression. Plant virus nanoparticles, including those derived from cowpea mosaic virus or tobacco mosaic virus in particular have shown promise as immunotherapies stimulating tumor-associated immune cells and as drug carriers delivering conjugated chemotherapeutics effectively to tumors. Advancements have also been made toward the development of lectins that can selectively recognize cancer cells. The ease at which plant systems can be utilized for the production of these products presents an opportunity to further develop novel and exciting anti-cancer biologics.

Molecular farming for therapies and vaccines in Africa

Local manufacturing of protein-based vaccines and therapies in Africa is limited and contributes to a trade deficit, security of supply concerns and poor access to biopharmaceuticals by the poor. Plant molecular farming is a potential technology solution that has received growing adoption by African scientists attracted by the potential for the competitive cost of goods, safety and efficacy. Plant-made pharmaceutical technologies for veterinary and human vaccination and treatment of non-communicable and infectious diseases are available at different stages of development in Africa. There is also growth in the translation of these technologies to commercial operations. Africa is poised to benefit from the real-world impact of molecular farming in the next few years.

Structural and In Vitro Functional Analyses of Novel Plant-Produced Anti-Human PD1 Antibody

Immunotherapy has emerged as a promising and effective treatment for cancer. The frequently used immunotherapy agents are immune checkpoint inhibitors, such as antibodies specific to PD1, PD-L1, or CTLA-4. However, these drugs are highly expensive, and most people in the world cannot access the treatment. The development of recombinant protein production platforms that are cost-effective, scalable, and safe is needed. Plant platforms are attractive because of their low production cost, speed, scalability, lack of human and animal pathogens, and post-translational modifications that enable them to produce effective monoclonal antibodies. In this study, an anti-PD1 IgG4 monoclonal antibody (mAb) was transiently produced in Nicotiana benthamiana leaves. The plant-produced anti-PD1 mAb was compared to the commercial nivolumab produced in CHO cells. Our results showed that both antibodies have similar protein structures, and the N-glycans on the plant-produced antibody lacks plant-specific structures. The PD1 binding affinity of the plant-produced and commercial nivolumab, determined by two different techniques, that is, enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR), are also comparable. Plant-produced nivolumab binds to human PD1 protein with high affinity and specificity, blocks the PD-1/PD-L1 interaction, and enhances T cell function, comparable to commercial nivolumab. These results confirmed that plant-produced anti-PD1 antibody has the potential to be effective agent for cancer immunotherapy.

Effects of N-Glycosylation on the Structure, Function, and Stability of a Plant-Made Fc-Fusion Anthrax Decoy Protein

Protein N-glycosylation is an important post-translational modification and has influences on a variety of biological processes at the cellular and molecular level, making glycosylation a major study aspect for glycoprotein-based therapeutics. To achieve a comprehensive understanding on how N-glycosylation impacts protein properties, an Fc-fusion anthrax decoy protein, viz rCMG2-Fc, was expressed in Nicotiana benthamiana plant with three types of N-glycosylation profiles. Three variants were produced by targeting protein to plant apoplast (APO), endoplasmic reticulum (ER) or removing the N-glycosylation site by a point mutation (Agly). Both the APO and ER variants had a complex-type N-glycan (GnGnXF) as their predominant glycans. In addition, ER variant had a higher concentration of mannose-type N-glycans (50%). The decoy protein binds to the protective antigen (PA) of anthrax through its CMG2 domain and inhibits toxin endocytosis. The protein expression, sequence, N-glycosylation profile, binding kinetics to PA, toxin neutralization efficiency, and thermostability were determined experimentally. In parallel, we performed molecular dynamics (MD) simulations of the predominant full-length rCMG2-Fc glycoform for each of the three N-glycosylation profiles to understand the effects of glycosylation at the molecular level. The MAN8 glycoform from the ER variant was additionally simulated to resolve differences between the APO and ER variants. Glycosylation showed strong stabilizing effects on rCMG2-Fc during in planta accumulation, evidenced by the over 2-fold higher expression and less protein degradation observed for glycosylated variants compared to the Agly variant. Protein function was confirmed by toxin neutralization assay (TNA), with effective concentration (EC₅₀) rankings from low to high of 67.6 ng/ml (APO), 83.15 ng/ml (Agly), and 128.9 ng/ml (ER). The binding kinetics between rCMG2-Fc and PA were measured with bio-layer interferometry (BLI), giving sub-nanomolar affinities regardless of protein glycosylation and temperatures (25 and 37°C). The protein thermostability was examined utilizing the PA binding ELISA to provide information on EC₅₀ differences. The fraction of functional ER variant decayed after overnight incubation at 37°C, and no significant change was observed for APO or Agly variants. In MD simulations, the MAN8 glycoform exhibits quantitatively higher distance between the CMG2 and Fc domains, as well as higher hydrophobic solvent accessible surface areas (SASA), indicating a possibly higher aggregation tendency of the ER variant. This study highlights the impacts of N-glycosylation on protein properties and provides insight into the effects of glycosylation on protein molecular dynamics.

Production of Biopharmaceuticals in Nicotiana benthamiana-Axillary Stem Growth as a Key Determinant of Total Protein Yield

Data are scarce about the influence of basic cultural conditions on growth patterns and overall performance of plants used as heterologous production hosts for protein pharmaceuticals. Higher plants are complex organisms with young, mature, and senescing organs that show distinct metabolic backgrounds and differ in their ability to sustain foreign protein expression and accumulation. Here, we used the transient protein expression host Nicotiana benthamiana as a model to map the accumulation profile of influenza virus hemagglutinin H1, a clinically promising vaccine antigen, at the whole plant scale. Greenhouse-grown plants submitted to different light regimes, submitted to apical bud pruning, or treated with the axillary growth-promoting cytokinin 6-benzylaminopurine were vacuum-infiltrated with agrobacteria harboring a DNA sequence for H1 and allowed to express the viral antigen for 7 days in growth chamber under similar environmental conditions. Our data highlight the importance of young leaves on H1 yield per plant, unlike older leaves which account for a significant part of the plant biomass but contribute little to total antigen titer. Our data also highlight the key contribution of axillary stem leaves, which contribute more than 50% of total yield under certain conditions despite representing only one-third of the total biomass. These findings underline the relevance of both considering main stem leaves and axillary stem leaves while modeling heterologous protein production in N. benthamiana. They also demonstrate the potential of exogenously applied growth-promoting hormones to modulate host plant architecture for improvement of protein yields.