Plant-based oral delivery of β-glucocerebrosidase as an enzyme replacement therapy for Gaucher's disease

Harnessing cells to improve transport of nanomedicines

Efficient tumour treatment is hampered by the poor selectivity of anticancer drugs, resulting in scarce tumour accumulation and undesired off-target effects. Nano-sized drug-delivery systems in the form of nanoparticles (NPs) have been proposed to improve drug distribution to solid tumours, by virtue of their ability of passive and active tumour targeting. Despite these advantages, literature studies indicated that less than 1% of the administered NPs can successfully reach the tumour mass, highlighting the necessity for more efficient drug transporters in cancer treatment. Living cells, such as blood cells, circulating immune cells, platelets, and stem cells, are often found as an infiltrating component in most solid tumours, because of their ability to naturally circumvent immune recognition, bypass biological barriers, and reach inaccessible tissues through innate tropism and active motility. Therefore, the tumour-homing ability of these cells can be harnessed to design living cell carriers able to improve the transport of drugs and NPs to tumours. Albeit promising, this approach is still in its beginnings and suffers from difficult scalability, high cost, and poor reproducibility. In this review, we present an overview of the most common cell transporters of drugs and NPs, and we discuss how different cell types interact with biological barriers to deliver cargoes of various natures to tumours. Finally, we analyse the different techniques used to load drugs or NPs in living cells and discuss their advantages and disadvantages.

Exploring recent progress of molecular farming for therapeutic and recombinant molecules in plant systems

An excellent technique for producing pharmaceuticals called "molecular farming" enables the industrial mass production of useful recombinant proteins in genetically modified organisms. Protein-based pharmaceuticals are rising in significance because of a variety of factors, including their bioreactivity, precision, safety, and efficacy rate. Heterologous expression methods for the manufacturing of pharmaceutical products have been previously employed using yeast, bacteria, and animal cells. However, the high cost of mammalian cell system, and production, the chance for product complexity, and contamination, and the hurdles of scaling up to commercial production are the limitations of these traditional expression methods. Plants have been raised as a hopeful replacement system for the expression of biopharmaceutical products due to their potential benefits, which include low production costs, simplicity in scaling up to commercial manufacturing levels, and a lower threat of mammalian toxin contaminations and virus infections. Since plants are widely utilized as a source of therapeutic chemicals, molecular farming offers a unique way to produce molecular medicines such as recombinant antibodies, enzymes, growth factors, plasma proteins, and vaccines whose molecular basis for use in therapy is well established. Biopharming provides more economical and extensive pharmaceutical drug supplies, including vaccines for contagious diseases and pharmaceutical proteins for the treatment of conditions like heart disease and cancer. To assess its technical viability and the efficacy resulting from the adoption of molecular farming products, the following review explores the various methods and methodologies that are currently employed to create commercially valuable molecules in plant systems.

Current Challenges of Vaccination in Fish Health Management

Vaccination is an essential method of immunological preventive care required for the health management of all animals, including fish. More particularly, immunization is necessary for in-land aquaculture to manage diseases in fish broodstocks and healthy seed production. According to the latest statistics in 2020, 90.3 million tons of capture fishery production was achieved from the aquaculture sector. Out of the above, 78.8 million tons were from marine water aquaculture sectors, and 11.5 million tons were from inland water aquaculture sectors. About a 4% decline in fish production was achieved in 2020 in comparison to 2018 from inland aquaculture sectors. On the other hand, the digestive protein content, healthy fats, and nutritional values of fish products are comparatively more affordable than in other meat sources. In 2014, about 10% of aquatic cultured animals were lost (costing global annual losses > USD 10 billion) due to infectious diseases. Therefore, vaccination in fish, especially in broodstocks, is one of the essential approaches to stop such losses in the aquaculture sector. Fish vaccines consist of whole-killed pathogens, protein subunits, recombinant proteins, DNA, or live-attenuated vaccines. Challenges persist in the adaption of vaccination in the aquaculture sector, the route of administration, the use of effective adjuvants, and, most importantly, the lack of effective results. The use of autogenous vaccines; vaccination via intramuscular, intraperitoneal, or oral routes; and, most importantly, adding vaccines in feed using top dressing methods or as a constituent in fish feed are now emerging. These methods will lower the risk of using antibiotics in cultured water by reducing environmental contamination.

Multidimensional futuristic approaches to address the pandemics beyond COVID-19

Globally, the impact of the coronavirus disease 2019 (COVID-19) pandemic has been enormous and unrelenting with ∼6.9 million deaths and ∼765 million infections. This review mainly focuses on the recent advances and potentially novel molecular tools for viral diagnostics and therapeutics with far-reaching implications in managing the future pandemics. In addition to briefly highlighting the existing and recent methods of viral diagnostics, we propose a couple of potentially novel non-PCR-based methods for rapid, cost-effective, and single-step detection of nucleic acids of viruses using RNA mimics of green fluorescent protein (GFP) and nuclease-based approaches. We also highlight key innovations in miniaturized Lab-on-Chip (LoC) devices, which in combination with cyber-physical systems, could serve as ideal futuristic platforms for viral diagnosis and disease management. We also discuss underexplored and underutilized antiviral strategies, including ribozyme-mediated RNA-cleaving tools for targeting viral RNA, and recent advances in plant-based platforms for rapid, low-cost, and large-scale production and oral delivery of antiviral agents/vaccines. Lastly, we propose repurposing of the existing vaccines for newer applications with a major emphasis on Bacillus Calmette-Guérin (BCG)-based vaccine engineering.

An overview of descriptors to capture protein properties - Tools and perspectives in the context of QSAR modeling

Proteins are important ingredients in food and feed, they are the active components of many pharmaceutical products, and they are necessary, in the form of enzymes, for the success of many technical processes. However, production can be challenging, especially when using heterologous host cells such as bacteria to express and assemble recombinant mammalian proteins. The manufacturability of proteins can be hindered by low solubility, a tendency to aggregate, or inefficient purification. Tools such as in silico protein engineering and models that predict separation criteria can overcome these issues but usually require the complex shape and surface properties of proteins to be represented by a small number of quantitative numeric values known as descriptors, as similarly used to capture the features of small molecules. Here, we review the current status of protein descriptors, especially for application in quantitative structure activity relationship (QSAR) models. First, we describe the complexity of proteins and the properties that descriptors must accommodate. Then we introduce descriptors of shape and surface properties that quantify the global and local features of proteins. Finally, we highlight the current limitations of protein descriptors and propose strategies for the derivation of novel protein descriptors that are more informative.

Bioencapsulation is a feasible method of terbinafine administration in Emydomyces testavorans-infected western pond turtles (Actinemys marmorata)

OBJECTIVE

To evaluate the pharmacokinetics of terbinafine administered to western pond turtles (Actinemys marmorata) via oral gavage and bioencapsulated in earthworms.

ANIMALS

7 western pond turtles.

PROCEDURES

A randomized complete crossover single-dose pharmacokinetic study was performed. Compounded terbinafine (25 mg/mL; 30 mg/kg) was administered through oral gavage (OG) directly into the stomach or bioencapsulated (BEC) into an earthworm vehicle. Blood (0.2 mL) was drawn from the jugular vein at 0, 0.5, 1, 2, 4, 8, 12, 24, 48, 72, and 120 hours after administration. Plasma terbinafine levels were measured using high-performance liquid chromatography.

RESULTS

Peak plasma terbinafine concentrations of 786.9 ± 911 ng/mL and 1,022.2 ± 911 were measured at 1.8 ± 2.8 and 14.1 ± 12.3 hours after OG and BEC administration, respectively. There was a significant (P = .031) increase in area under the curve with BEC compared to OG. Using steady-state predictions, with once-daily terbinafine administration, 3/7 and 7/7 turtles had plasma concentrations persistently greater than the minimum inhibitory concentration (MIC) for Emydomyces testavorans for the OG and BEC administration routes of administration, respectively. With administration every 48 hours, 3/7 turtles for the OG phase and 6/7 turtles for the BEC phase had concentrations greater than the E. testavorans MIC throughout the entire dosing interval.

CLINICAL RELEVANCE

Administration of terbinafine (30 mg/kg) every 24 or 48 hours via earthworm bioencapsulation in western pond turtles may be appropriate for the treatment of shell lesions caused by E. testavorans. Clinical studies are needed to assess the efficacy of treatment.

Unconventional Secretion of Plant Extracellular Vesicles and Their Benefits to Human Health: A Mini Review

Mechanisms devoted to the secretion of proteins via extracellular vesicles (EVs) have been found in mammals, yeasts, and plants. Since they transport a number of leader-less proteins to the plasma membrane or the extracellular space, EVs are considered part of Unconventional protein secretion (UPS) routes. UPS involving EVs are a relatively new field in plants. Aside from their role in plant physiology and immunity, plant extracts containing EVs have also been shown to be beneficial for human health. Therefore, exploring the use of plant EVs in biomedicine and their potential as drug delivery tools is an exciting avenue. Here we give a summary of the state of knowledge on plant EVs, their crosstalk with mammalian systems and potential research routes that could lead to practical applications in therapeutic drug delivery.

Plant-Based Vaccines: Antigen Design, Diversity, and Strategies for High Level Production

Vaccines for human use have conventionally been developed by the production of (1) microbial pathogens in eggs or mammalian cells that are then inactivated, or (2) by the production of pathogen proteins in mammalian and insect cells that are purified for vaccine formulation, as well as, more recently, (3) by using RNA or DNA fragments from pathogens. Another approach for recombinant antigen production in the last three decades has been the use of plants as biofactories. Only have few plant-produced vaccines been evaluated in clinical trials to fight against diseases, of which COVID-19 vaccines are the most recent to be FDA approved. In silico tools have accelerated vaccine design, which, combined with transitory antigen expression in plants, has led to the testing of promising prototypes in pre-clinical and clinical trials. Therefore, this review deals with a description of immunoinformatic tools and plant genetic engineering technologies used for antigen design (virus-like particles (VLP), subunit vaccines, VLP chimeras) and the main strategies for high antigen production levels. These key topics for plant-made vaccine development are discussed and perspectives are provided.

Oral delivery of therapeutic proteins bioencapsulated in plant cells: preclinical and clinical advances

Oral delivery of protein drugs (PDs) made in plant cells could revolutionize current approaches of their production and delivery. Expression of PDs reduces their production cost by elimination of prohibitively expensive fermentation, purification, cold transportation/storage, and sterile injections and increases their shelf life for several years. Ability of plant cell wall to protect PDs from digestive acids/enzymes, commensal bacteria to release PDs in gut lumen after lysis of plant cell wall and role of GALT in inducing tolerance facilitate prevention or treatment allergic, autoimmune diseases or anti-drug antibody responses. Delivery of functional proteins facilitate treatment of inherited or metabolic disorders. Recent advances in making PDs free of antibiotic resistance genes in edible plant cells, long-term storage at ambient temperature maintaining their efficacy, production in cGMP facilities, IND enabling studies for clinical advancement and FDA approval of orally delivered PDs augur well for advancing this novel drug delivery platform technology.

Comparative whole-genome and proteomics analyses of the next seed bank and the original master seed bank of MucoRice-CTB 51A line, a rice-based oral cholera vaccine

BACKGROUND

We have previously developed a rice-based oral vaccine against cholera diarrhea, MucoRice-CTB. Using Agrobacterium-mediated co-transformation, we produced the selection marker-free MucoRice-CTB line 51A, which has three copies of the cholera toxin B subunit (CTB) gene and two copies of an RNAi cassette inserted into the rice genome. We determined the sequence and location of the transgenes on rice chromosomes 3 and 12. The expression of alpha-amylase/trypsin inhibitor, a major allergen protein in rice, is lower in this line than in wild-type rice. Line 51A was self-pollinated for five generations to fix the transgenes, and the seeds of the sixth generation produced by T5 plants were defined as the master seed bank (MSB). T6 plants were grown from part of the MSB seeds and were self-pollinated to produce T7 seeds (next seed bank; NSB). NSB was examined and its whole genome and proteome were compared with those of MSB.

RESULTS

We re-sequenced the transgenes of NSB and MSB and confirmed the positions of the three CTB genes inserted into chromosomes 3 and 12. The DNA sequences of the transgenes were identical between NSB and MSB. Using whole-genome sequencing, we compared the genome sequences of three NSB with three MSB samples, and evaluated the effects of SNPs and genomic structural variants by clustering. No functionally important mutations (SNPs, translocations, deletions, or inversions of genic regions on chromosomes) between NSB and MSB samples were detected. Analysis of salt-soluble proteins from NSB and MSB samples by shot-gun MS/MS detected no considerable differences in protein abundance. No difference in the expression pattern of storage proteins and CTB in mature seeds of NSB and MSB was detected by immuno-fluorescence microscopy.

CONCLUSIONS

All analyses revealed no considerable differences between NSB and MSB samples. Therefore, NSB can be used to replace MSB in the near future.

Expression of Colorectal Cancer Antigenic Protein Fused to IgM Fc in Chinese Cabbage (Brassica rapa)

The epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen and a potential target for tumor vaccine. The EpCAM is a cell-surface glycoprotein highly expressed in colorectal carcinomas. The objective of the present study is to develop an edible vaccine system through Agrobacterium-mediated transformation in Chinese cabbage (Brassica rapa). For the transformation, two plant expression vectors containing genes encoding for the EpCAM recombinant protein along with the fragment crystallizable (Fc) region of immunoglobulin M (IgM) and Joining (J)-chain tagged with the KDEL endoplasmic reticulum retention motif (J-chain K) were constructed. The vectors were successfully transformed and expressed in the Chinese cabbage individually using Agrobacterium. The transgenic Chinese cabbages were screened using genomic polymerase chain reaction (PCR) in T₀ transgenic plant lines generated from both transformants. Similarly, the immunoblot analysis revealed the expression of recombinant proteins in the transformants. Further, the T₁ transgenic plants were generated by selfing the transgenic plants (T₀) carrying EpCAM-IgM Fc and J-chain K proteins, respectively. Subsequently, the T₁ plants generated from EpCAM-IgM Fc and J-chain K transformants were crossed to generate F₁ plants carrying both transgenes. The presence of both transgenes was validated using PCR in the F₁ plants. In addition, the expression of Chinese cabbage-derived EpCAM-IgM Fc × J-chain K was evaluated using immunoblot and ELISA analyses in the F₁ plants. The outcomes of the present study can be utilized for the development of a potential anti-cancer vaccine candidate using Chinese cabbage.

Inducible expression of antigens in plants: a study focused on peptides related to multiple sclerosis immunotherapy

Multiple sclerosis (MS) affects 2.3 million patients worldwide with no effective treatments available thus far. Depletion of autoreactive T-cells is considered the basis for immunotherapeutic approaches. For this purpose the peptides BV5S2, BV6S5, and BV13S1 have been identified as candidates for the development of a MS vaccine. Herein, the plant-based simultaneous production of these peptides is described as an effort to generate a new model of MS immunotherapy. A polyprotein comprising the sequence of the target peptides was designed having the picornaviral 2A sequence in between to mediate the release of the individual peptides upon translation. A codon optimized gene was cloned in vectors mediating constitutive (CaMV35S promoter) or inducible (AlcA promoter) expression. No transgenic tobacco plants were recovered from the constitutive vector suggesting toxicity of the target peptides. In contrast, several transformed lines were obtained with the inducible vector. The individual BV5S2, BV6S5, and BV13S1 peptides were detected in transformed lines upon ethanol-mediated induction and a quantitative analysis based on a OVA conjugate carrying the three peptides revealed accumulation levels up to 0.5 μg g-1 FW leaves. The plant-made peptides were able to induce humoral responses in orally immunized mice. This platform will be useful in the development of alternative immunotherapies against MS having low cost and safety as main attributes. Moreover the platform represents an attractive alternative for the expression of antigens having detrimental effects in plants.

Enzyme therapy: a forerunner in catalyzing a healthy society?

INTRODUCTION

The use of enzymes in various industries has been prevalent for centuries. However, their potency as therapeutics remained latent until the late 1950 s, when scientists finally realized the gold mine they were sitting on. Enzyme therapy has seen rapid development over the past few decades and has been widely used for the therapy of myriad diseases, including lysosomal storage disorders, cancer, Alzheimer's disease, irritable bowel syndrome, exocrine pancreatic insufficiency, and hyperuricemia. Enzymes are also used for wound healing, the treatment of microbial infections, and gene therapy.

AREAS COVERED

This is a comprehensive review of the therapeutic use of enzymes that can act as a guidepost for researchers and academicians and presents a general overview of the developments in enzyme therapy over the years, along with updates on recent advancements in enzyme therapy research.

EXPERT OPINION

Although enzyme therapy is immensely beneficial and induces little auxiliary damage, it has several drawbacks, ranging from high cost, low stability, low production, and hyperimmune responses to the failure to cure a variety of the problems associated with a disease. Further fine-tuning and additional clinical efficacy studies are required to establish enzyme therapy as a forerunner to catalyzing a healthy society.

Oral delivery of novel human IGF-1 bioencapsulated in lettuce cells promotes musculoskeletal cell proliferation, differentiation and diabetic fracture healing

Human insulin-like growth factor-1 (IGF-1) plays important roles in development and regeneration of skeletal muscles and bones but requires daily injections or surgical implantation. Current clinical IGF-1 lacks e-peptide and is glycosylated, reducing functional efficacy. In this study, codon-optimized Pro-IGF-1 with e-peptide (fused to GM1 receptor binding protein CTB or cell penetrating peptide PTD) was expressed in lettuce chloroplasts to facilitate oral delivery. Pro-IGF-1 was expressed at high levels in the absence of the antibiotic resistance gene in lettuce chloroplasts and was maintained in subsequent generations. In lyophilized plant cells, Pro-IGF-1 maintained folding, assembly, stability and functionality up to 31 months, when stored at ambient temperature. CTB-Pro-IGF-1 stimulated proliferation of human oral keratinocytes, gingiva-derived mesenchymal stromal cells and mouse osteoblasts in a dose-dependent manner and promoted osteoblast differentiation through upregulation of ALP, OSX and RUNX2 genes. Mice orally gavaged with the lyophilized plant cells significantly increased IGF-1 levels in sera, skeletal muscles and was stable for several hours. When bioencapsulated CTB-Pro-IGF-1 was gavaged to femoral fractured diabetic mice, bone regeneration was significantly promoted with increase in bone volume, density and area. This novel delivery system should increase affordability and patient compliance, especially for treatment of musculoskeletal diseases.

In Vitro Biocompatibility of Decellularized Cultured Plant Cell-Derived Matrices

There has been a recent increase in exploring the use of decellularized plant tissue as a novel "green" material for biomedical applications. As part of this effort, we have developed a technique to decellularize cultured plant cells (tobacco BY-2 cells and rice cells) and tissue (tobacco hairy roots) that uses deoxyribonuclease I (DNase I)). As a proof of concept, all cultured plant cells and tissue were transformed to express recombinant enhanced green fluorescent protein (EGFP) to show that the proteins of interest could be retained within the matrices. Decellularization of lyophilized tobacco BY-2 cells with DNase for 30 min depleted the DNA content from 1503 ± 459 to 31 ± 5 ng/sample. The decellularization procedure resulted in approximately 36% total protein retention (154 ± 60 vs 424 ± 70 μg/sample) and 33% EGFP retention. Similar results for DNA removal and protein retention were observed with the rice cells and tobacco hairy root matrices. When exposed to decellularized BY-2 cell-derived matrices, monolayer cultures of human foreskin fibroblasts (hFFs) maintained or increased metabolic activity, which is an indicator of cell viability. Furthermore, hFFs were able to attach, spread, and proliferate when cultured with the decellularized BY-2 cell-derived matrices in an aggregate model. Overall, these studies demonstrate that cultured plant cells and tissue can be effectively decellularized with DNase I with substantial protein retention. The resulting material has a positive impact on hFF metabolic activity and could be employed to create a three-dimensional environment for cell growth. These results thus show the promise of using naturally derived cellulose matrices from cultured plant cells and tissues for biomedical applications.

High Level Production of Monoclonal Antibodies Using an Optimized Plant Expression System

Biopharmaceuticals are a large and fast-growing sector of the total pharmaceutical market with antibody-based therapeutics accounting for over 100 billion USD in sales yearly. Mammalian cells are traditionally used for monoclonal antibody production, however plant-based expression systems have significant advantages. In this work, we showcase recent advances made in plant transient expression systems using optimized geminiviral vectors that can efficiently produce heteromultimeric proteins. Two, three, or four fluorescent proteins were coexpressed simultaneously, reaching high yields of 3–5 g/kg leaf fresh weight or ~50% total soluble protein. As a proof-of-concept for this system, various antibodies were produced using the optimized vectors with special focus given to the creation and production of a chimeric broadly neutralizing anti-flavivirus antibody. The variable regions of this murine antibody, 2A10G6, were codon optimized and fused to a human IgG1. Analysis of the chimeric antibody showed that it was efficiently expressed in plants at 1.5 g of antibody/kilogram of leaf tissue, can be purified to near homogeneity by a simple one-step purification process, retains its ability to recognize the Zika virus envelope protein, and potently neutralizes Zika virus. Two other monoclonal antibodies were produced at similar levels (1.2–1.4 g/kg). This technology will be a versatile tool for the production of a wide spectrum of pharmaceutical multi-protein complexes in a fast, powerful, and cost-effective way.

Arabidopsis Hairy Roots Producing High Level of Active Human Gastric Lipase

Arabidopsis hairy roots were used to produce human gastric lipase. When treated with 2,4-D, the hairy roots developed into thick organs that produced more protein than untreated roots. This was first assessed using green fluorescent protein-producing root lines from which the protein diffused into the culture medium. When growing hairy roots which express the human gastric lipase gene, very little lipase was found in the medium. Incubating the roots in a low pH buffer resulted in lipase diffusion into the buffer, avoiding the need for grinding. The activity of the enzyme on 4-methylumbellireryl-oleate and on tributyrin was determined. Approximately 6000 units of enzyme were recovered per gram of root. The enzyme was also extracted from freeze-dried roots before and after a 2-month storage period at room temperature. This work demonstrates the relevance of Arabidopsis hairy roots for the production of human gastric lipase.

Expression of a Functional Recombinant Human Glycogen Debranching Enzyme (hGDE) in N. benthamiana Plants and in Hairy Root Cultures

BACKGROUND

Glycogen storage disease type III (GSDIII, Cori/Forbes disease) is a metabolic disorder due to the deficiency of the Glycogen Debranching Enzyme (GDE), a large monomeric protein (about 176 kDa) with two distinct enzymatic activities: 4-α-glucantransferase and amylo-α-1,6-glucosidase. Several mutations along the amylo-alpha-1,6-glucosidase,4-alphaglucanotransferase (Agl) gene are associated with loss of enzymatic activity. The unique treatment for GSDIII, at the moment, is based on diet. The potential of plants to manufacture exogenous engineered compounds for pharmaceutical purposes, from small to complex protein molecules such as vaccines, antibodies and other therapeutic/prophylactic entities, was shown by modern biotechnology through "Plant Molecular Farming".

OBJECTIVE AND METHODS

In an attempt to develop novel protein-based therapeutics for GSDIII, the Agl gene, encoding for the human GDE (hGDE) was engineered for expression as a histidinetagged GDE protein both in Nicotiana benthamiana plants by a transient expression approach, and in axenic hairy root in vitro cultures (HR) from Lycopersicum esculentum and Beta vulgaris.

RESULTS

In both plant-based expression formats, the hGDE protein accumulated in the soluble fraction of extracts. The plant-derived protein was purified by affinity chromatography in native conditions showing glycogen debranching activity.

CONCLUSION

These investigations will be useful for the design of a new generation of biopharmaceuticals based on recombinant GDE protein that might represent, in the future, a possible therapeutic option for GSDIII.

Biomimetic and bioinspired strategies for oral drug delivery

Oral drug delivery remains the most preferred approach due to its multiple advantages. Recently there has been increasing interest in the development of advanced vehicles for oral delivery of different therapeutics. Among them, biomimetic and bioinspired strategies are emerging as novel approaches that are promising for addressing biological barriers encountered by traditional drug delivery systems. Herein we provide a state-of-the-art review on the current progress of biomimetic particulate oral delivery systems. Different biomimetic nanoparticles used for oral drug delivery are first discussed, mainly including ligand/antibody-functionalized nanoparticles, transporter-mediated nanoplatforms, and nanoscale extracellular vesicles. Then we describe bacteria-derived biomimetic systems, with respect to oral delivery of therapeutic proteins or antigens. Subsequently, yeast-derived oral delivery systems, based on either chemical engineering or bioengineering approaches are discussed, with emphasis on the treatment of inflammatory diseases and cancer as well as oral vaccination. Finally, bioengineered plant cells are introduced for oral delivery of biological agents. A future perspective is also provided to highlight the existing challenges and possible resolution toward clinical translation of currently developed biomimetic oral therapies.

An overview of tolerogenic immunotherapies based on plant-made antigens

INTRODUCTION

Over the last two decades, genetically engineered plants became attractive and mature platforms for producing vaccines and other relevant biopharmaceuticals. Autoimmune and inflammatory disorders demand the availability of accessible treatments, and one alternative therapy is based on therapeutic vaccines able to downregulate immune responses that favor pathology progression.

AREAS COVERED

The current status of plant-made tolerogenic vaccines is presented with emphasis on the candidates under evaluation in test animals. Nowadays, this concept has been assessed in models of food and pollen allergies, autoimmune diabetes, asthma, arthritis, and prevention of blocking antibodies induction against a biopharmaceutical used in replacement therapies.

EXPERT OPINION

According to the current evidence generated at the preclinical level, plant-made tolerogenic therapies are a promise to treat several immune-related conditions, and the beginning of clinical trials is envisaged for the next decade. Advantages and limitations for this technology are discussed.

Molecular farming of antimicrobial peptides: available platforms and strategies for improving protein biosynthesis using modified virus vectors

The constant demand for new antibiotic drugs has driven efforts by the scientific community to prospect for peptides with a broad spectrum of action. In this context, antimicrobial peptides (AMPs) have acquired great scientific importance in recent years due to their ability to possess antimicrobial and immunomodulatory activity. In the last two decades, plants have attracted the interest of the scientific community and industry as regards their potential as biofactories of heterologous proteins. One of the most promising approaches is the use of viral vectors to maximize the transient expression of drugs in the leaves of the plant Nicotiana benthamiana. Recently, the MagnifectionTM expression system was launched. This sophisticated commercial platform allows the assembly of the viral particle in leaf cells and the systemic spread of heterologous protein biosynthesis in green tissues caused by Agrobacterium tumefaciens "gene delivery method". The system also presents increased gene expression levels mediated by potent viral expression machinery. These characteristics allow the mass recovery of heterologous proteins in the leaves of N. benthamiana in 8 to 10 days. This system was highly efficient for the synthesis of different classes of pharmacological proteins and contains enormous potential for the rapid and abundant biosynthesis of AMPs.

Green Therapeutic Biocapsules: Using Plant Cells to Orally Deliver Biopharmaceuticals

The use of innovative platforms to produce biopharmaceuticals cheaply and deliver them through noninvasive routes could expand their social benefits. Coverage should increase as a consequence of lower cost and higher patient compliance due to painless administration. For more than two decades of research, oral therapies that rely on genetically engineered plants for the production of biopharmaceuticals have been explored to treat or prevent high-impact diseases. Recent reports on the successful oral delivery of plant-made biopharmaceuticals raise new hopes for the field. Several candidates have shown protection in animal models, and efforts to establish their production on an industrial scale are ongoing. These advances and perspectives for the field are analyzed.

Engineering Plants for the Future: Farming with Value-Added Harvest

Plants and their rich variety of natural compounds are used to maintain and to improve health since the earliest stages of civilization. Despite great advances in synthetic organic chemistry, one fourth of present-day drugs have still a botanical origin, and we are currently living a revival of interest in new pharmaceuticals from plant sources.

Modern biotechnology has defined the potential of plants to be systems able to manufacture not only molecules naturally occurring in plants but also newly engineered compounds, from small to complex protein molecules, which may originate even from non-plant sources. Among these compounds, pharmaceuticals such as vaccines, antibodies and other therapeutic or prophylactic entities can be listed. For this technology, the term plant molecular farming has been coined with reference to agricultural applications due to the use of crops as biofactories for the production of high-added value molecules. In this perspective, edible plants have also been thought as a tool to deliver by the oral route recombinant compounds of medical significance for new therapeutic strategies. Despite many hurdles in establishing regulatory paths for this “novel” biotechnology, plants as bioreactors deserve more attention when considering their intrinsic advantages, such as the quality and safety of the recombinant molecules that can be produced and their potential for large-scale and low-cost production, despite worrying issues (e.g. amplification and diffusion of transgenes) that are mainly addressed by regulations, if not already tackled by the plant-made products already commercialized. The huge benefits generated by these valuable products, synthesized through one of the safest, cheapest and most efficient method, speak for themselves.

Milestone for plant-based recombinant protein production for human health use was the approval in 2012 by the US Food and Drug Administration of plant-made taliglucerase alfa, a therapeutic enzyme for the treatment of Gaucher’s disease, synthesized in carrot suspension cultures by Protalix BioTherapeutics.

In this review, we will go through the various approaches and results for plant-based production of proteins and recent progress in the development of plant-made pharmaceuticals (PMPs) for the prevention and treatment of human diseases. An analysis on acceptance of these products by public opinion is also tempted.

Assessment of Carrot Callus as Biofactories of an Atherosclerosis Oral Vaccine Prototype

Atherosclerosis is a pathology leading to cardiovascular diseases with high epidemiologic impact; thus, new therapies are required to fight this global health issue. Immunotherapy is a feasible approach to treat atherosclerosis and given that genetically engineered plants are attractive hosts for vaccine development; we previously proved that the plant cell is able to synthesize a chimeric protein called CTB:p210:CETPe, which is composed of the cholera toxin B subunit (CTB) as immunogenic carrier and target epitopes from the cholesteryl ester transfer protein (CETP_461-476) and apolipoprotein B100 (p210). Since CTB:p210:CETPe was expressed in tobacco at sufficient levels to evoke humoral responses in mice, its expression in carrot was explored in the present study looking to develop a vaccine in a safe host amenable for oral delivery; avoiding the purification requirement. Carrot cell lines expressing CTB:p210:CETPe were developed, showing accumulation levels up to 6.1 µg/g dry weight. An immunoblot analysis revealed that the carrot-made protein is antigenic and an oral mice immunization scheme led to evidence on the immunogenic activity of this protein; revealing its capability of inducing serum IgG responses against p210 and CETP epitopes. This study represents a step forward in the development of an attractive oral low-cost vaccine to treat atherosclerosis.

Bioreactor-Based Production of Glycoproteins in Plant Cell Suspension Cultures

Recombinant glycoproteins such as monoclonal antibodies have a major impact on modern healthcare systems, e.g., as the active pharmaceutical ingredients in anticancer drugs. A specific glycan profile is often necessary to achieve certain desirable activities, such as the effector functions of an antibody, receptor binding or a sufficient serum half-life. However, many expression systems produce glycan profiles that differ substantially from the preferred form (usually the form found in humans) or produce a diverse array of glycans with a range of in vivo activities, thus necessitating laborious and costly separation and purification processes. In contrast, protein glycosylation in plant cells is much more homogeneous than other systems, with only one or two dominant forms. Additionally, these glycan profiles tend to remain stable when the process and cultivation conditions are changed, making plant cells an ideal expression system to produce recombinant glycoproteins with uniform glycan profiles in a consistent manner. This chapter describes a protocol that uses fermentations using plant cell cultures to produce glycosylated proteins using two different types of bioreactors, a classical autoclavable STR 3-L and a wave reactor.

Platforms for Plant-Based Protein Production

Plant molecular farming depends on a diversity of plant systems for production of useful recombinant proteins. These proteins include protein biopolymers, industrial proteins and enzymes, and therapeutic proteins. Plant production systems include microalgae, cells, hairy roots, moss, and whole plants with both stable and transient expression. Production processes involve a narrowing diversity of bioreactors for cell, hairy root, microalgae, and moss cultivation. For whole plants, both field and automated greenhouse cultivation methods are used with products expressed and produced either in leaves or seeds. Many successful expression systems now exist for a variety of different products with a list of increasingly successful commercialized products. This chapter provides an overview and examples of the current state of plant-based production systems for different types of recombinant proteins.

Using transgenic plants and modified plant viruses for the development of treatments for human diseases

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Concept of plant-based biofactories for therapeutics and biologics.

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Industrial preference of transient expression system — agroinfiltration.

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Advancement of virus-like particles from epitope presentation to nanomedicine.

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Recent progress of plant-made therapeutics and biologics against human diseases.

Production of proteins in plants for human health applications has become an attractive strategy attributed by their potentials for low-cost production, increased safety due to the lack of human or animal pathogens, scalability and ability to produce complex proteins. A major milestone for plant-based protein production for use in human health was achieved when Protalix BioTherapeutics produced taliglucerase alfa (Elelyso^®) in suspension cultures of a transgenic carrot cell line for the treatment of patients with Gaucher's disease, was approved by the USA Food and Drug Administration in 2012. In this review, we are highlighting various approaches for plant-based production of proteins and recent progress in the development of plant-made therapeutics and biologics for the prevention and treatment of human diseases.

Enrichment of apoplastic fluid with therapeutic recombinant protein for efficient biofarming

OBJECTIVE

For efficient biofarming we attempted to enrich plant interstitial fluid (IF)/apoplastic fluid with targeted recombinant therapeutic protein. We employed a synthetic human Glucocerebrosidase (GCB), a model biopharmaceutical protein gene in this study.

RESULTS

Twenty one Nicotiana varieties, species and hybrids were initially screened for individual IF recovery and based on the findings, we selected Nicotiana tabacum NN (S-9-6), Nicotiana tabacum nn (S-9-7) and Nicotiana benthamiana (S-6-6) as model plants for raising transgenic expressing GCB via Agrobacterium mediated transformation under the control of M24 promoter; GCB specific activity in each transgenic lines were analyzed and we observed higher concentration of recombinant GCB in IF of these transgenic lines (S-9-6, S-9-7, and S-6-6) in comparison to their concentration in crude leaf extracts.

CONCLUSION

Recovery of valuable therapeutics in plant IF as shown in the present study holds great promise for promoting plant based biofarming. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:726-736, 2017.

A Perspective on the Development of Plant-Made Vaccines in the Fight against Ebola Virus

The Ebola virus (EBOV) epidemic indicated a great need for prophylactic and therapeutic strategies. The use of plants for the production of biopharmaceuticals is a concept being adopted by the pharmaceutical industry, with an enzyme for human use currently commercialized since 2012 and some plant-based vaccines close to being commercialized. Although plant-based antibodies against EBOV are under clinical evaluation, the development of plant-based vaccines against EBOV essentially remains an unexplored area. The current technologies for the production of plant-based vaccines include stable nuclear expression, transient expression mediated by viral vectors, and chloroplast expression. Specific perspectives on how these technologies can be applied for developing anti-EBOV vaccines are provided, including possibilities for the design of immunogens as well as the potential of the distinct expression modalities to produce the most relevant EBOV antigens in plants considering yields, posttranslational modifications, production time, and downstream processing.

Oral Tolerance Induction in Hemophilia B Dogs Fed with Transplastomic Lettuce

Anti-drug antibodies in hemophilia patients substantially complicate treatment. Their elimination through immune tolerance induction (ITI) protocols poses enormous costs, and ITI is often ineffective for factor IX (FIX) inhibitors. Moreover, there is no prophylactic ITI protocol to prevent anti-drug antibody (ADA) formation. Using general immune suppression is problematic. To address this urgent unmet medical need, we delivered antigen bioencapsulated in plant cells to hemophilia B dogs. Commercial-scale production of CTB-FIX fusion expressed in lettuce chloroplasts was done in a hydroponic facility. CTB-FIX (∼1 mg/g) in lyophilized cells was stable with proper folding, disulfide bonds, and pentamer assembly after 30-month storage at ambient temperature. Robust suppression of immunoglobulin G (IgG)/inhibitor and IgE formation against intravenous FIX was observed in three of four hemophilia B dogs fed with lyophilized lettuce cells expressing CTB-FIX. No side effects were detected after feeding CTB-FIX-lyophilized plant cells for >300 days. Coagulation times were markedly shortened by intravenous FIX in orally tolerized treated dogs, in contrast to control dogs that formed high-titer antibodies to FIX. Commercial-scale production, stability, prolonged storage of lyophilized cells, and efficacy in tolerance induction in a large, non-rodent model of human disease offer a novel concept for oral tolerance and low-cost production and delivery of biopharmaceuticals.

Cold chain and virus-free chloroplast-made booster vaccine to confer immunity against different poliovirus serotypes

The WHO recommends complete withdrawal of oral polio vaccine (OPV) type 2 by April 2016 globally and replacing with at least one dose of inactivated poliovirus vaccine (IPV). However, high-cost, limited supply of IPV, persistent circulating vaccine-derived polioviruses transmission and need for subsequent boosters remain unresolved. To meet this critical need, a novel strategy of a low-cost cold chain-free plant-made viral protein 1 (VP1) subunit oral booster vaccine after single IPV dose is reported. Codon optimization of the VP1 gene enhanced expression by 50-fold in chloroplasts. Oral boosting of VP1 expressed in plant cells with plant-derived adjuvants after single priming with IPV significantly increased VP1-IgG1 and VP1-IgA titres when compared to lower IgG1 or negligible IgA titres with IPV injections. IgA plays a pivotal role in polio eradication because of its transmission through contaminated water or sewer systems. Neutralizing antibody titres (~3.17-10.17 log2 titre) and seropositivity (70-90%) against all three poliovirus Sabin serotypes were observed with two doses of IPV and plant-cell oral boosters but single dose of IPV resulted in poor neutralization. Lyophilized plant cells expressing VP1 stored at ambient temperature maintained efficacy and preserved antigen folding/assembly indefinitely, thereby eliminating cold chain currently required for all vaccines. Replacement of OPV with this booster vaccine and the next steps in clinical translation of FDA-approved antigens and adjuvants are discussed.

Biomanufacturing of protective antibodies and other therapeutics in edible plant tissues for oral applications

Although plant expression systems used for production of therapeutic proteins have the advantage of being scalable at a low price, the downstream processing necessary to obtain pure therapeutic molecules is as expensive as for the traditional Chinese hamster ovary (CHO) platforms. However, when edible plant tissues (EPTs) are used, there is no need for exhaustive purification, because they can be delivered orally as partially purified formulations that are safe for consumption. This economic benefit is especially interesting when high doses of recombinant proteins are required throughout the treatment/prophylaxis period, as is the case for antibodies used for oral passive immunization (OPI). The secretory IgA (SIgA) antibodies, which are highly abundant in the digestive tract and mucosal secretions, and thus the first choice for OPI, have only been successfully produced in plant expression systems. Here, we cover most of the up-to-date examples of EPT-produced pharmaceuticals, including two examples of SIgA aimed at oral delivery. We describe the benefits and drawbacks of delivering partially purified formulations and discuss a number of practical considerations and criteria to take into account when using plant expression systems, such as subcellular targeting, protein degradation, glycosylation patterns and downstream strategies, all crucial for improved yield, high quality and low cost of the final product.

The Potential for Microalgae as Bioreactors to Produce Pharmaceuticals

As photosynthetic organisms, microalgae can efficiently convert solar energy into biomass. Microalgae are currently used as an important source of valuable natural biologically active molecules, such as carotenoids, chlorophyll, long-chain polyunsaturated fatty acids, phycobiliproteins, carotenoids and enzymes. Significant advances have been achieved in microalgae biotechnology over the last decade, and the use of microalgae as bioreactors for expressing recombinant proteins is receiving increased interest. Compared with the bioreactor systems that are currently in use, microalgae may be an attractive alternative for the production of pharmaceuticals, recombinant proteins and other valuable products. Products synthesized via the genetic engineering of microalgae include vaccines, antibodies, enzymes, blood-clotting factors, immune regulators, growth factors, hormones, and other valuable products, such as the anticancer agent Taxol. In this paper, we briefly compare the currently used bioreactor systems, summarize the progress in genetic engineering of microalgae, and discuss the potential for microalgae as bioreactors to produce pharmaceuticals.

Oral Delivery of Protein Drugs Bioencapsulated in Plant Cells

Plants cells are now approved by the FDA for cost-effective production of protein drugs (PDs) in large-scale current Good Manufacturing Practice (cGMP) hydroponic growth facilities. In lyophilized plant cells, PDs are stable at ambient temperature for several years, maintaining their folding and efficacy. Upon oral delivery, PDs bioencapsulated in plant cells are protected in the stomach from acids and enzymes but are subsequently released into the gut lumen by microbes that digest the plant cell wall. The large mucosal area of the human intestine offers an ideal system for oral drug delivery. When tags (receptor-binding proteins or cell-penetrating peptides) are fused to PDs, they efficiently cross the intestinal epithelium and are delivered to the circulatory or immune system. Unique tags to deliver PDs to human immune or nonimmune cells have been developed recently. After crossing the epithelium, ubiquitous proteases cleave off tags at engineered sites. PDs are also delivered to the brain or retina by crossing the blood–brain or retinal barriers. This review highlights recent advances in PD delivery to treat Alzheimer's disease, diabetes, hypertension, Gaucher's or ocular diseases, as well as the development of affordable drugs by eliminating prohibitively expensive purification, cold chain and sterile delivery.

The potential of plants as a system for the development and production of human biologics

The growing promise of plant-made biologics is highlighted by the success story of ZMapp™ as a potentially life-saving drug during the Ebola outbreak of 2014-2016. Current plant expression platforms offer features beyond the traditional advantages of low cost, high scalability, increased safety, and eukaryotic protein modification. Novel transient expression vectors have been developed that allow the production of vaccines and therapeutics at unprecedented speed to control potential pandemics or bioterrorism attacks. Plant-host engineering provides a method for producing proteins with unique and uniform mammalian post-translational modifications, providing opportunities to develop biologics with increased efficacy relative to their mammalian cell-produced counterparts. Recent demonstrations that plant-made proteins can function as biocontrol agents of foodborne pathogens further exemplify the potential utility of plant-based protein production. However, resolving the technical and regulatory challenges of commercial-scale production, garnering acceptance from large pharmaceutical companies, and obtaining U.S. Food and Drug Administration approval for several major classes of biologics are essential steps to fulfilling the untapped potential of this technology.

The potential of plants as a system for the development and production of human biologics

The growing promise of plant-made biologics is highlighted by the success story of ZMapp™ as a potentially life-saving drug during the Ebola outbreak of 2014-2016. Current plant expression platforms offer features beyond the traditional advantages of low cost, high scalability, increased safety, and eukaryotic protein modification. Novel transient expression vectors have been developed that allow the production of vaccines and therapeutics at unprecedented speed to control potential pandemics or bioterrorism attacks. Plant-host engineering provides a method for producing proteins with unique and uniform mammalian post-translational modifications, providing opportunities to develop biologics with increased efficacy relative to their mammalian cell-produced counterparts. Recent demonstrations that plant-made proteins can function as biocontrol agents of foodborne pathogens further exemplify the potential utility of plant-based protein production. However, resolving the technical and regulatory challenges of commercial-scale production, garnering acceptance from large pharmaceutical companies, and obtaining U.S. Food and Drug Administration approval for several major classes of biologics are essential steps to fulfilling the untapped potential of this technology.

Large-scale production of pharmaceutical proteins in plant cell culture-the Protalix experience

Protalix Biotherapeutics develops recombinant human proteins and produces them in plant cell culture. Taliglucerase alfa has been the first biotherapeutic expressed in plant cells to be approved by regulatory authorities around the world. Other therapeutic proteins are being developed and are currently at various stages of the pipeline. This review summarizes the major milestones reached by Protalix Biotherapeutics to enable the development of these biotherapeutics, including platform establishment, cell line selection, manufacturing process and good manufacturing practice principles to consider for the process. Examples of the various products currently being developed are also presented.