Molecular farming expression of recombinant fusion proteins applied to skincare strategies.

This review discusses the current research progress in molecular farming technology in the field of skincare, with an emphasis on molecular farming expression strategies. The strategies of transdermal drug delivery and their advantages are also highlighted. The expression of cosmetically relevant fused proteins has become an important way to enhance the efficacy of the proteins. Therefore, we also discuss the feasibility and strategies for expressing fusion proteins in A. thaliana, specifically the fusion of Epidermal growth factor (EGF) to a cell-penetrating peptide (CPP), in which the production can be greatly enhanced via plant expression systems since these systems offer higher biosecurity, flexibility, and expansibility than prokaryotic, animal and mammalian expression systems. While the fusion of EGF to CCP can enhance its transdermal ability, the effects of the fusion protein on skin repair, melasma, whitening, and anti-aging are poorly explored. Beyond this, fusing proteins with transdermal peptides presents multiple possibilities for the development of tissue repair and regeneration therapeutics, as well as cosmetics and beauty products. As certain plant extracts are known to contain proteins beneficial for skin health, the expression of these proteins in plant systems will better maintain their integrity and biological activities, thereby facilitating the development of more effective skincare products.

Utilizing Plant Protein Secretion System for Pharmaceutical Protein Production.

Molecular farming, also known as plant molecular farming (PMF), is a technique that involves using plants and plant cells as bioreactors to produce recombinant proteins. This is a cost-effective and sustainable way of producing large quantities of proteins for various applications, including pharmaceuticals, vaccines, and industrial enzymes. An endogenous or exogenous signal peptide (SP) is flanked at the N-terminal for recombinant protein targeting and storage. These SPs are responsible for guiding the recombinant protein products to the correct destination within the plant cell or facilitating their secretion into the extracellular space. In this chapter, we will give a brief introduction of the current PMF research outcomes supported by the basic study of vesicle trafficking and protein secretion, mainly introducing the bright yellow 2 (BY-2) cell-based secretion pathway and its associated protocols according to our study of recombinant human iduronidase.

Towards a seamless product and process development workflow for recombinant proteins produced by plant molecular farming.

Plant molecular farming (PMF) has been promoted as a fast, efficient and cost-effective alternative to bacteria and animal cells for the production of biopharmaceutical proteins. Numerous plant species have been tested to produce a wide range of drug candidates. However, PMF generally lacks a systematic, streamlined and seamless workflow to continuously fill the product pipeline. Therefore, it is currently unable to compete with established platforms in terms of routine, throughput and horizontal integration (the rapid translation of product candidates to preclinical and clinical development). Individual management decisions, limited funding and a lack of qualified production capacity can hinder the execution of such projects, but we also lack suitable technologies for sample handling and data management. This perspectives article will highlight current bottlenecks in PMF and offer potential solutions that combine PMF with existing technologies to build an integrated facility of the future for product development, testing, manufacturing and clinical translation. Ten major bottlenecks have been identified and are discussed in turn: automated cloning and simplified transformation options, reproducibility of bacterial cultivation, bioreactor integration with automated cell handling, options for rapid mid-scale candidate and product manufacturing, interconnection with (group-specific or personalized) clinical trials, diversity of (post-)infiltration conditions, development of downstream processing platforms, continuous process operation, compliance of manufacturing conditions with biosafety regulations, scaling requirements for cascading biomass.

Molecular farming for sustainable production of clinical-grade antimicrobial peptides.

Antimicrobial peptides (AMPs) are emerging as next-generation therapeutics due to their broad-spectrum activity against drug-resistant bacterial strains and their ability to eradicate biofilms, modulate immune responses, exert anti-inflammatory effects and improve disease management. They are produced through solid-phase peptide synthesis or in bacterial or yeast cells. Molecular farming, i.e. the production of biologics in plants, offers a low-cost, non-toxic, scalable and simple alternative platform to produce AMPs at a sustainable cost. In this review, we discuss the advantages of molecular farming for producing clinical-grade AMPs, advances in expression and purification systems and the cost advantage for industrial-scale production. We further review how 'green' production is filling the sustainability gap, streamlining patent and regulatory approvals and enabling successful clinical translations that demonstrate the future potential of AMPs produced by molecular farming. Finally, we discuss the regulatory challenges that need to be addressed to fully realize the potential of molecular farming-based AMP production for therapeutics.

Bacterial growth-mediated systems remodelling of Nicotiana benthamiana defines unique signatures of target protein production in molecular pharming.

The need for therapeutics to treat a plethora of medical conditions and diseases is on the rise and the demand for alternative approaches to mammalian-based production systems is increasing. Plant-based strategies provide a safe and effective alternative to produce biological drugs but have yet to enter mainstream manufacturing at a competitive level. Limitations associated with batch consistency and target protein production levels are present; however, strategies to overcome these challenges are underway. In this study, we apply state-of-the-art mass spectrometry-based proteomics to define proteome remodelling of the plant following agroinfiltration with bacteria grown under shake flask or bioreactor conditions. We observed distinct signatures of bacterial protein production corresponding to the different growth conditions that directly influence the plant defence responses and target protein production on a temporal axis. Our integration of proteomic profiling with small molecule detection and quantification reveals the fluctuation of secondary metabolite production over time to provide new insight into the complexities of dual system modulation in molecular pharming. Our findings suggest that bioreactor bacterial growth may promote evasion of early plant defence responses towards Agrobacterium tumefaciens (updated nomenclature to Rhizobium radiobacter). Furthermore, we uncover and explore specific targets for genetic manipulation to suppress host defences and increase recombinant protein production in molecular pharming.

Proteomic Profiling of Interplay Between Agrobacterium tumefaciens and Nicotiana benthamiana for Improved Molecular Pharming Outcomes.

Transient expression of recombinant proteins in plants is being used as a platform for production of therapeutic proteins. Benefits of this system include a reduced cost of drug development, rapid delivery of new products to the market, and an ability to provide safe and efficacious medicines for diseases. Although plant-based production systems offer excellent potential for therapeutic protein production, barriers, such as plant host defense response, exist which negatively impact the yield of product. Here we provide a protocol using tandem mass tags and mass spectrometry-based proteomics to quickly and robustly quantify the change in abundance of host defense proteins produced during the production process. These proteins can then become candidates for genetic manipulation to create host plants with reduced plant defenses capable of producing higher therapeutic protein yields.

Improving Protein Quantity and Quality-The Next Level of Plant Molecular Farming.

Plants offer several unique advantages in the production of recombinant pharmaceuticals for humans and animals. Although numerous recombinant proteins have been expressed in plants, only a small fraction have been successfully put into use. The hugely distinct expression systems between plant and animal cells frequently cause insufficient yield of the recombinant proteins with poor or undesired activity. To overcome the issues that greatly constrain the development of plant-produced pharmaceuticals, great efforts have been made to improve expression systems and develop alternative strategies to increase both the quantity and quality of the recombinant proteins. Recent technological revolutions, such as targeted genome editing, deconstructed vectors, virus-like particles, and humanized glycosylation, have led to great advances in plant molecular farming to meet the industrial manufacturing and clinical application standards. In this review, we discuss the technological advances made in various plant expression platforms, with special focus on the upstream designs and milestone achievements in improving the yield and glycosylation of the plant-produced pharmaceutical proteins.

AgroLux: bioluminescent Agrobacterium to improve molecular pharming and study plant immunity.

Agroinfiltration in Nicotiana benthamiana is widely used to transiently express heterologous proteins in plants. However, the state of Agrobacterium itself is not well studied in agroinfiltrated tissues, despite frequent studies of immunity genes conducted through agroinfiltration. Here, we generated a bioluminescent strain of Agrobacterium tumefaciens GV3101 to monitor the luminescence of Agrobacterium during agroinfiltration. By integrating a single copy of the lux operon into the genome, we generated a stable 'AgroLux' strain, which is bioluminescent without affecting Agrobacterium growth in vitro and in planta. To illustrate its versatility, we used AgroLux to demonstrate that high light intensity post infiltration suppresses both Agrobacterium luminescence and protein expression. We also discovered that AgroLux can detect Avr/Cf-induced immune responses before tissue collapse, establishing a robust and rapid quantitative assay for the hypersensitive response (HR). Thus, AgroLux provides a non-destructive, versatile and easy-to-use imaging tool to monitor both Agrobacterium and plant responses.

A Brief Overview of Potential Treatments for Viral Diseases Using Natural Plant Compounds: The Case of SARS-Cov.

The COVID-19 pandemic, as well as the more general global increase in viral diseases, has led researchers to look to the plant kingdom as a potential source for antiviral compounds. Since ancient times, herbal medicines have been extensively applied in the treatment and prevention of various infectious diseases in different traditional systems. The purpose of this review is to highlight the potential antiviral activity of plant compounds as effective and reliable agents against viral infections, especially by viruses from the coronavirus group. Various antiviral mechanisms shown by crude plant extracts and plant-derived bioactive compounds are discussed. The understanding of the action mechanisms of complex plant extract and isolated plant-derived compounds will help pave the way towards the combat of this life-threatening disease. Further, molecular docking studies, in silico analyses of extracted compounds, and future prospects are included. The in vitro production of antiviral chemical compounds from plants using molecular pharming is also considered. Notably, hairy root cultures represent a promising and sustainable way to obtain a range of biologically active compounds that may be applied in the development of novel antiviral agents.

Synthetic Promoters from Strawberry Vein Banding Virus (SVBV) and Dahlia Mosaic Virus (DaMV).

We have constructed two intra-molecularly shuffled promoters, namely S100 and D100. The S100 recombinant promoter (621 bp) was generated by ligation of 250 bp long upstream activation sequence (UAS) of Strawberry vein banding virus (SV10UAS; - 352 to - 102 relative to TSS) with its 371 bp long TATA containing core promoter domain (SV10CP; - 352 to + 19). Likewise, 726 bp long D100 promoter was constructed by fusion of 170 bp long UAS of Dahlia mosaic virus (DaMV14UAS; - 203 to - 33) with its 556 bp long core promoter domain (DaMV4CP; - 474 to + 82). S100 and D100 promoters showed 1.8 and 2.2 times stronger activities than that of the CaMV35S promoter. The activity of the promoters is comparable to that of the CaMV35S2 promoter. Transcript analysis employing qRT-PCR and histochemical assays supported the above findings. Abscisic acid and salicylic acid induce the activity of the D100 promoter. Leaf protein obtained from Nicotiana tabacum plant expressing NSD2 gene (Nigella sativa L. defensin 2) driven by the D100 promoter showed antifungal activity against Alternaria alternata and Phoma exigua var. exigua and antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus. Strong S100 and D100 promoters have potential to become efficient candidates for plant metabolic engineering and molecular pharming.

Quantitative proteomic profiling of shake flask versus bioreactor growth reveals distinct responses of Agrobacterium tumefaciens for preparation in molecular pharming.

The preparation of Agrobacterium tumefaciens cultures with strains encoding proteins intended for therapeutic or industrial purposes is an important activity prior to treatment of plants for transient expression of valuable protein products. The rising demand for biologic products such as these underscores the expansion of molecular pharming and warrants the need to produce transformed plants at an industrial scale. This requires large quantities of A. tumefaciens culture, which is challenging using traditional growth methods (e.g., shake flask). To overcome this limitation, we investigate the use of bioreactors as an alternative to shake flasks to meet production demands. Here, we observe differences in bacterial growth among the tested parameters and define conditions for consistent bacterial culturing between shake flask and bioreactor. Quantitative proteomic profiling of cultures from each growth condition defines unique growth-specific responses in bacterial protein abundance and highlights the functional roles of these proteins, which may influence bacterial processes important for effective agroinfiltration and transformation. Overall, our study establishes and optimizes comparable growth conditions for shake flask versus bioreactors and provides novel insights into fundamental biological processes of A. tumefaciens influenced by such growth conditions.

Modulation of Barley (Hordeum vulgare L.) Grain Protein Sink-Source Relations Towards Human Epidermal Growth Factor Instead of B-hordein Storage Protein.

Seeds have evolutionarily developed to store protein without immediately degrading it and constitute ideal tissues for recombinant protein storage. Unfortunately, the production of recombinant protein in seeds is compromised by low yield as compared to other heterologous expression systems. In order to improve the yield of the human epidermal growth factor (EGF) in barley, protein sink-source relations in the developing grain were modulated towards EGF instead of the barley storage protein. The EGF gene, under the control of a B-hordein and a seed-specific oat globulin promoter, was introduced by crossing EGF lines into the Risø 56 mutant deficient in B-hordein storage protein synthesis. Offspring plants were analysed for EGF and Hordein expression and for expression of the unfolded protein response (UPR) genes PDI and CRT to monitor changes in ER stress levels. EGF content was increased significantly in the mature grain of homozygous offspring and PDI and CRT gene expressions were upregulated. We demonstrate, for the first time in barley, that replacement of an abundant seed storage protein with a specific heterologous protein driven by the promoter of the removed gene can accelerate the production of a specific heterologous protein in barley grains.

A New Plant Expression System for Producing Pharmaceutical Proteins.

In the past decade, interest in the production of recombinant pharmaceutical proteins in plants has tremendously progressed because plants do not harbor mammalian viruses, are economically competitive, easily scalable, and capable of carrying out complex post-translational modifications required for recombinant pharmaceutical proteins. Mucuna bracteata is an essential perennial cover crop species widely planted as an underground cover in oil palm and rubber plantations. As a legume, they have high biomass, thrive in its habitat, and can fix nitrogen. Thus, M. bracteata is a cost-efficient crop that shows ideal characteristics as a platform for mass production of recombinant protein. In this study, we established a new platform for the transient production of a recombinant protein in M. bracteata via vacuum-assisted agro-infiltration. Five-week-old M. bracteata plants were vacuum infiltrated with Agrobacterium tumefaciens harboring a plasmid that encodes for an anti-toxoplasma immunoglobulin (IgG) under different parameters, including trifoliate leaf positional effects, days to harvest post-infiltration, and the Agrobacterium strain used. Our results showed that vacuum infiltration of M. bracteata plant with A. tumefaciens strain GV3101 produced the highest concentration of heterologous protein in its bottom trifoliate leaf at 2 days post-infiltration. The purified anti-toxoplasma IgG was then analyzed using Western blot and ELISA. It was demonstrated that, while structural heterogeneity existed in the purified anti-toxoplasma IgG from M. bracteata, its transient expression level was two-fold higher than the model platform, Nicotiana benthamiana. This study has laid the foundation towards establishing M. bracteata as a potential platform for the production of recombinant pharmaceutical protein.

Plant Serine Protease Inhibitors: Biotechnology Application in Agriculture and Molecular Farming.

The serine protease inhibitors (SPIs) are widely distributed in living organisms like bacteria, fungi, plants, and humans. The main function of SPIs as protease enzymes is to regulate the proteolytic activity. In plants, most of the studies of SPIs have been focused on their physiological role. The initial studies carried out in plants showed that SPIs participate in the regulation of endogenous proteolytic processes, as the regulation of proteases in seeds. Besides, it was observed that SPIs also participate in the regulation of cell death during plant development and senescence. On the other hand, plant SPIs have an important role in plant defense against pests and phytopathogenic microorganisms. In the last 20 years, several transgenic plants over-expressing SPIs have been produced and tested in order to achieve the increase of the resistance against pathogenic insects. Finally, in molecular farming, SPIs have been employed to minimize the proteolysis of recombinant proteins expressed in plants. The present review discusses the potential biotechnological applications of plant SPIs in the agriculture field.

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.

Coloring biology in grape skin: a prospective strategy for molecular farming.

Grapevine is one of the earliest domesticated fruit crops that has been widely prized and cultivated for its fruit and wine. Grapes exhibit a wide range of colors, ranging from the green/yellow to the dark blue tones according to the amount and composition of anthocyanin. During the last decades, many studies regarding the genetic control of the grape color in European, American and Asian cultivars have been well documented. DNA binding genes for several transcription factors, such as MYBA1 and MYBA2 haplotype compositions at the color locus are the key determinant of anthocyanin diversity and grape skin color development. Retrotransposon in the MYBA1 promoter region and mutation in MYBA2 coding sequence resulted in a white-skinned grape. The MYB haplotypes affect the ratio of tri/di-hydroxylated anthocyanins and methylated/non-methylated anthocyanins through the regulation of several structural genes involved in the anthocyanin biosynthesis, resulting in diverse colored tones. The present review provides an overview of the current state of the molecular mechanisms underlying the genetic regulations of the anthocyanin accumulation and diversification in grapes. The hypothesized models described in this review is a step forward to potentially predict the color diversification in different grape cultivars, which translate the advances in fundamental plant biology toward the application of grape molecular breeding.

Molecular Farming in Barley: Development of a Novel Production Platform to Produce Human Antimicrobial Peptide LL-37.

The peptide LL-37, a component of the human innate immune system, represents a promising drug candidate. In particular, the development of low-cost production platform technology is a critical bottleneck in its use in medicine. In the present study, a viable approach for the LL-37 production in transgenic barley is developed. First, comparative analyses of the effects of different fused peptide epitope tags applicable for accumulation and purification on LL-37 production yield are performed using transient expression in tobacco leaves. Following the selection of the most yielding fusion peptide strategies, eight different constructs for the expression of codon optimized chimeric LL-37 genes in transgenic barley plants are created. The expression of individual constructs is driven either by an endosperm-specific promoter of the barley B1 hordein gene or by the maize ubiquitin promoter. The transgenes are stably integrated into the barley genome and inherited in the subsequent generation. All transgenic lines show normal phenotypes and are fertile. LL-37 accumulated in the barley seeds up to 0.55 mg per 1 kg of grain. The fused epitope tags are cleaved off by the use of enterokinase. Furthermore, in planta produced LL-37 including the fused versions is biologically active.

Synthetic gene design-The rationale for codon optimization and implications for molecular pharming in plants.

Degeneracy in the genetic code allows multiple codon sequences to encode the same protein. Codon usage bias in genes is the term given to the preferred use of particular synonymous codons. Synonymous codon substitutions had been regarded as "silent" as the primary structure of the protein was not affected; however, it is now accepted that synonymous substitutions can have a significant effect on heterologous protein expression. Codon optimization, the process of altering codons within the gene sequence to improve recombinant protein expression, has become widely practised. Multiple inter-linked factors affecting protein expression need to be taken into consideration when optimizing a gene sequence. Over the years, various computer programmes have been developed to aid in the gene sequence optimization process. However, as the rulebook for altering codon usage to affect protein expression is still not completely understood, it is difficult to predict which strategy, if any, will design the "optimal" gene sequence. In this review, codon usage bias and factors affecting codon selection will be discussed and the evidence for codon optimization impact will be reviewed for recombinant protein expression using plants as a case study. These developments will be relevant to all recombinant expression systems; however, molecular pharming in plants is an area which has consistently encountered difficulties with low levels of recombinant protein expression, and should benefit from an evidence based rational approach to synthetic gene design. Biotechnol. Bioeng. 2017;114: 492-502. © 2016 Wiley Periodicals, Inc.

Micropropagation of transgenic lettuce containing HBsAg as a method of mass-scale production of standardised plant material for biofarming purposes.

KEY MESSAGE: Micropropagation protocol of transgenic lettuce bearing S-, M- and L-HBsAg was developed for increased production of uniformised material for oral vaccine preparation. Effective manufacturing of plant-based biopharmaceuticals, including oral vaccines, depends on sufficient content of a protein of interest in the initial material and its efficient conversion into an administrable formulation. However, stable production of plants with a uniformised antigen content is equally important for reproducible processing. This can be provided by micropropagation techniques. Here, we present a protocol for micropropagation of transgenic lettuce lines bearing HBV surface antigens: S-, M- and L-HBsAg. These were multiplied through axillary buds to avoid the risk of somaclonal variation. Micropropagation effectiveness reached 3.5-5.7 per passage, which implies potential production of up to 6600 plant clones within a maximum 5 months. Multiplication and rooting rates were statistically homogenous for most transgenic and control plants. For most lines, more than 90 % of clones obtained via in vitro micropropagation had HBsAg content as high as reference plants directly developed from seeds. Clones were also several times more uniform in HBsAg expression. Variation coefficients of HBsAg content did not exceed 10 % for approximately 40-85 % of clones, or reached a maximum 20 % for 90 % of all clones. Tissue culture did not affect total and leaf biomass yields. Seed production for clones was decreased insignificantly and did not impact progeny condition. Micropropagation facilitates a substantial increase in the production of lettuce plants with high and considerably equalised HBsAg contents. This, together with the previously reported optimisation of plant tissue processing and its long-term stability, constitutes a successive step in manufacturing of a standardised anti-HBV oral vaccine of reliable efficacy.

Recombinant biologic products versus nutraceuticals from plants - a regulatory choice?

Biotechnology has transformed the potential for plants to be a manufacturing source of pharmaceutical compounds. Now, with transgenic and transient expression techniques, virtually any biologic, including vaccines and therapeutics, could be manufactured in plants. However, uncertainty over the regulatory path for such new pharmaceuticals has been a deterrent. Consideration has been given to using alternative regulatory paths, including those for nutraceuticals or cosmetic agents. This review will consider these possibilities, and discuss the difficulties in establishing regulatory guidelines for new pharmaceutical manufacturing technologies.