Recombinant production of bovine Lactoferrin-derived antimicrobial peptide in tobacco hairy roots expression system

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.

Heterologous Production of Antimicrobial Peptides: Notes to Consider

Heavy and irresponsible use of antibiotics in the last century has put selection pressure on the microbes to evolve even faster and develop more resilient strains. In the confrontation with such sometimes called "superbugs", the search for new sources of biochemical antibiotics seems to have reached the limit. In the last two decades, bioactive antimicrobial peptides (AMPs), which are polypeptide chains with less than 100 amino acids, have attracted the attention of many in the control of microbial pathogens, more than the other types of antibiotics. AMPs are groups of components involved in the immune response of many living organisms, and have come to light as new frontiers in fighting with microbes. AMPs are generally produced in minute amounts within organisms; therefore, to address the market, they have to be either produced on a large scale through recombinant DNA technology or to be synthesized via chemical methods. Here, heterologous expression of AMPs within bacterial, fungal, yeast, plants, and insect cells, and points that need to be considered towards their industrialization will be reviewed.

Recombinant production of antimicrobial peptides in plants

Classical plant breeding methods are limited in their ability to confer disease resistance on plants. However, in recent years, advancements in molecular breeding and biotechnological have provided new approaches to overcome these limitations and protect plants from disease. Antimicrobial peptides (AMPs) constitute promising agents that may be able to protect against infectious agents. Recently, peptides have been recombinantly produced in plants at scale and low cost. Because AMPs are less likely than conventional antimicrobials to elicit resistance of pathogenic bacteria, they open up exciting new avenues for agricultural applications. Here, we review recent advances in the design and production of bioactive recombinant AMPs that can effectively protect crop plants from diseases.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

Nicotiana hairy roots for recombinant protein expression, where to start? A systematic review

BACKGROUND

Hairy roots are a plant-tissue culture raised by Rhizobium rhizogenes infection (formerly known as Agrobacterium rhizogenes). Nowadays, these roots have been gaining more space in biotechnology due to their benefits for the recombinant expression of valuables proteins; it includes simplified downstream processing, protein rhizosecretion, and scalability in bioreactors. However, due to methodological inconsistency among reports, the tissue platform is still a promising technology.

METHODS AND RESULTS

In the current paper, we propose the first step to overcome this issue through a systematic review of studies that employ Nicotiana hairy roots for recombinant expression. We conducted a qualitative synthesis of 36 out of 387 publications initially selected. Following the PRISMA procedure, all papers were assessed for exclusion and inclusion criteria. Multiple points of root culture were explored, including transformation methods, root growth curve, external additives, and scale-up with bioreactors to determine which approaches performed best and what is still required to achieve a robust protocol.

CONCLUSION

The information presented here may help researchers who want to work with hairy roots in their laboratories trace a successful path to appraisal the literature status.

Green Antimicrobials as Therapeutic Agents for Diabetic Foot Ulcers

Diabetic foot ulcers (DFU) are one of the most serious and devastating complications of diabetes and account for a significant decrease in quality of life and costly healthcare expenses worldwide. This condition affects around 15% of diabetic patients and is one of the leading causes of lower limb amputations. DFUs generally present poor clinical outcomes, mainly due to the impaired healing process and the elevated risk of microbial infections which leads to tissue damage. Nowadays, antimicrobial resistance poses a rising threat to global health, thus hampering DFU treatment and care. Faced with this reality, it is pivotal to find greener and less environmentally impactful alternatives for fighting these resistant microbes. Antimicrobial peptides are small molecules that play a crucial role in the innate immune system of the host and can be found in nature. Some of these molecules have shown broad-spectrum antimicrobial properties and wound-healing activity, making them good potential therapeutic compounds to treat DFUs. This review aims to describe antimicrobial peptides derived from green, eco-friendly processes that can be used as potential therapeutic compounds to treat DFUs, thereby granting a better quality of life to patients and their families while protecting our fundamental bio-resources.

Lactoferrin and its role in biotechnological strategies for plant defense against pathogens

Agricultural crops are susceptible to many diseases caused by various pathogens, such as viruses, bacteria and fungi. This paper reviews the general principles of plant protection against pathogens, as well as the role of iron and antimicrobial peptide metabolism in plant immunity. The article highlights the principles of antibacterial, fungicidal and antiviral action of lactoferrin, a mammalian secretory glycoprotein, and lactoferrin peptides, and their role in protecting plants from phytopathogens. This review offers a comprehensive analysis and shows potential prospects of using the lactoferrin gene to enhance plant resistance to various phytopathogens, as well as the advantages of this biotechnological approach over existing methods of protecting plants against various diseases.

Strategies for improving antimicrobial peptide production

Antimicrobial peptides (AMPs) found in a wide range of animal, insect, and plant species are host defense peptides forming an integral part of their innate immunity. Although the exact mode of action of some AMPs is yet to be deciphered, many exhibit membrane lytic activity or interact with intracellular targets. The ever-growing threat of antibiotic resistance has brought attention to research on AMPs to enhance their clinical use as a therapeutic alternative. AMPs have several advantages over antibiotics such as broad range of antimicrobial activities including anti-fungal, anti-viral and anti-bacterial, and have not reported to contribute to resistance development. Despite the numerous studies to develop efficient production methods for AMPs, limitations including low yield, degradation, and loss of activity persists in many recombinant approaches. In this review, we outline available approaches for AMP production and various expression systems used to achieve higher yield and quality. In addition, recent advances in recombinant strategies, suitable fusion protein partners, and other molecular engineering strategies for improved AMP production are surveyed.

Successful use of Nicotiana tabacum hairy roots for the recombinant production of Cecropin A peptide

Cecropin A, as an antimicrobial peptide (AMP), is possible to use in medical and agricultural fields as a new and safe biocontrol agent. Therefore, it is highly necessary to find a cost-effective and scalable approach to generate a large scale of it. In this research, the Agrobacterium rhizogenes strain ATCC 15834 was used to transfer the Cecropin A gene to the Nicotiana tabacum. After confirmation of transgenic hairy roots, the antibacterial activity of purified Cecropin A peptide was measured using the agar gel diffusion method. Successful transforming of Cecropin A was confirmed at the RNA and protein levels in hairy root cells using RT-PCR and enzyme-linked immunosorbent assay (ELISA), respectively. The highest Cecropin A amount was detected in line 4 of the transgenic lines using ELISA in comparison with the nontransgenic line. Subsequently, the antimicrobial activity of Cecropin A extracted from line 4 showed the highest inhibition activity against Aspergillus niger. Besides, this activity was stable against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans pathogens after 7 days. The recombinant production of Cecropin A AMP had a yield of 63.81 μg/g of fresh weight. According to a significant yield, this system can be used to produce the Cecropin A peptide for pharmacological and food science applications.

Long-Lasting Stable Expression of Human LL-37 Antimicrobial Peptide in Transgenic Barley Plants

Antimicrobial peptides play a crucial role in the innate immune system of multicellular organisms. LL-37 is the only known member of the human cathelicidin family. As well as possessing antibacterial properties, it is actively involved in various physiological responses in eukaryotic cells. Accordingly, there is considerable interest in large-scale, low-cost, and microbial endotoxin-free production of LL-37 recombinant peptides for pharmaceutical applications. As a heterologous expression biofactory, we have previously obtained homologous barley (Hordeum vulgare L.) as an attractive vehicle for producing recombinant human LL-37 in the grain storage compartment, endosperm. The long-term stability of expression and inheritance of transgenes is necessary for the successful commercialization of recombinant proteins. Here, we report the stable inheritance and expression of the LL-37 gene in barley after six generations, including two consecutive seasons of experimental field cultivation. The transgenic plants showed normal growth and remained fertile. Based on the bacteria viability test, the produced peptide LL-37 retained high antibacterial activity.

Biotechnological Insights on the Expression and Production of Antimicrobial Peptides in Plants

The emergence of drug-resistant pathogens poses a serious critical threat to global public health and requires immediate action. Antimicrobial peptides (AMPs) are a class of short peptides ubiquitously found in all living forms, including plants, insects, mammals, microorganisms and play a significant role in host innate immune system. These peptides are considered as promising candidates to treat microbial infections due to its distinct advantages over conventional antibiotics. Given their potent broad spectrum of antimicrobial action, several AMPs are currently being evaluated in preclinical/clinical trials. However, large quantities of highly purified AMPs are vital for basic research and clinical settings which is still a major bottleneck hindering its application. This can be overcome by genetic engineering approaches to produce sufficient amount of diverse peptides in heterologous host systems. Recently plants are considered as potential alternatives to conventional protein production systems such as microbial and mammalian platforms due to their unique advantages such as rapidity, scalability and safety. In addition, AMPs can also be utilized for development of novel approaches for plant protection thereby increasing the crop yield. Hence, in order to provide a spotlight for the expression of AMP in plants for both clinical or agricultural use, the present review presents the importance of AMPs and efforts aimed at producing recombinant AMPs in plants for molecular farming and plant protection so far.

Determination of the Qualitative Composition of Biologically Active Substances of Extracts of In Vitro Callus, Cell Suspension, and Root Cultures of the Medicinal Plant Rhaponticum carthamoides

This work aims to study the qualitative composition of biologically active substance (BAS) extracts in vitro callus, cell suspension, and root cultures of the medicinal plant Rhaponticum carthamoides. The research methodology is based on high-performance liquid chromatography, and 1H nuclear magnetic resonance (NMR) spectra, to study the qualitative and quantitative analysis of BAS. The results of the qualitative composition analysis of the dried biomass extracts of in vitro callus, cell suspension and root cultures showed that the main biologically active substances in the medicinal plant Rhaponticum carthamoides are 2-deoxy-5,20,26-trihydroxyecdyson (7 mg, yield 0.12%), 5,20,26-trihydroxyecdyson 20,22-acetonide (15 mg, yield 0.25%), 2-deoxy-5,20,26-trihydroxyecdyson 20,22-acetonide (6 mg, yield 0.10%), 20,26-dihydroxyecdyson 20,22-acetonidecdyson 20,22-acetonide (5 mg, yield 0.09%), and ecdyson 20,22-acetonide (6 mg, yield 0.10%). In the future, it is planned to study the antimicrobial, antioxidant, and antitumor activity of BAS of extracts of in vitro callus, cell suspension, and root cultures of the medicinal plant Rhaponticum carthamoides, for the production of pharmaceuticals and dietary supplements with antitumor, antimicrobial and antioxidant effects.

Lactoferrin-derived peptides antimicrobial activity: an in vitro experiment

Antibiotic resistance is a global problem, searching for new antimicrobial agents is an urgent need. In this study, in vitro antibacterial and antimicrobial effects of milk-derived antimicrobial agents, lactoferrin-derived peptides, lactoferricin (Lfc) and lactoferrampin (Lfa) (alone or in combination) and their association with natural extracts have been explored. The assessment of antimicrobial activity was based on two measurements: Minimum Inhibitory Concentration and Fractional Inhibitory Concentration indexes. Lfc alone is more suitable for inhibiting Staphylococcus intermedius and Malassezia pachydermatis, while Lfa against Candida albicans, a synergistic effect of the two peptides against all the three pathogens has been detected. A strong synergy of all the natural extracts with Lfc and Lfa solution against selected microorganisms in vitro was pointed out. Our results suggest that natural-derived compounds, such as milk peptides and vegetal extracts could be promising tools to treat moderate fungal and bacterial infections.

Biotechnological Exploration of Transformed Root Culture for Value-Added Products

Medicinal plants produce valuable secondary metabolites with anticancer, analgesic, anticholinergic or other activities, but low metabolite levels and limited available tissue restrict metabolite yields. Transformed root cultures, also called hairy roots, provide a feasible approach for producing valuable secondary metabolites. Various strategies have been used to enhance secondary metabolite production in hairy roots, including increasing substrate availability, regulating key biosynthetic genes, multigene engineering, combining genetic engineering and elicitation, using transcription factors (TFs), and introducing new genes. In this review, we focus on recent developments in hairy roots from medicinal plants, techniques to boost production of desired secondary metabolites, and the development of new technologies to study these metabolites. We also discuss recent trends, emerging applications, and future perspectives.

Antifungal Peptides as Therapeutic Agents

Fungi have been used since ancient times in food and beverage-making processes and, more recently, have been harnessed for the production of antibiotics and in processes of relevance to the bioeconomy. Moreover, they are starting to gain attention as a key component of the human microbiome. However, fungi are also responsible for human infections. The incidence of community-acquired and nosocomial fungal infections has increased considerably in recent decades. Antibiotic resistance development, the increasing number of immunodeficiency- and/or immunosuppression-related diseases and limited therapeutic options available are triggering the search for novel alternatives. These new antifungals should be less toxic for the host, with targeted or broader antimicrobial spectra (for diseases of known and unknown etiology, respectively) and modes of actions that limit the potential for the emergence of resistance among pathogenic fungi. Given these criteria, antimicrobial peptides with antifungal properties, i.e., antifungal peptides (AFPs), have emerged as powerful candidates due to their efficacy and high selectivity. In this review, we provide an overview of the bioactivity and classification of AFPs (natural and synthetic) as well as their mode of action and advantages over current antifungal drugs. Additionally, natural, heterologous and synthetic production of AFPs with a view to greater levels of exploitation is discussed. Finally, we evaluate the current and potential applications of these peptides, along with the future challenges relating to antifungal treatments.

Hairy Root Cultures-A Versatile Tool With Multiple Applications

Hairy roots derived from the infection of a plant by Rhizobium rhizogenes (previously referred to as Agrobacterium rhizogenes) bacteria, can be obtained from a wide variety of plants and allow the production of highly diverse molecules. Hairy roots are able to produce and secrete complex active glycoproteins from a large spectrum of organisms. They are also adequate to express plant natural biosynthesis pathways required to produce specialized metabolites and can benefit from the new genetic tools available to facilitate an optimized production of tailor-made molecules. This adaptability has positioned hairy root platforms as major biotechnological tools. Researchers and industries have contributed to their advancement, which represents new alternatives from classical systems to produce complex molecules. Now these expression systems are ready to be used by different industries like pharmaceutical, cosmetics, and food sectors due to the development of fully controlled large-scale bioreactors. This review aims to describe the evolution of hairy root generation and culture methods and to highlight the possibilities offered by hairy roots in terms of feasibility and perspectives.

Targeting microbial pathogens by expression of new recombinant dermaseptin peptides in tobacco

Dermaseptin B1 (DrsB1), an antimicrobial cationic 31 amino acid peptide, is produced by Phyllomedusa bicolor. In an attempt to enhance the antimicrobial efficacy of DrsB1, the DrsB1 encoding 93 bp sequence was either fused to the N or C terminus of sequence encoding chitin-binding domain (CBD) of Avr4 gene from Cladosporium fulvum. Tobacco leaf disk explants were inoculated with Agrobacterium rhizogenes harboring pGSA/CBD-DrsB1 and pGSA/DrsB1-CBD expression vectors to produce hairy roots (HRs). Polymerase chain reaction (PCR) was employed to screen putative transgenic tobacco lines. Semi-quantitative RT-PCR and western blotting analysis indicated that the expression of recombinant genes were significantly higher, and recombinant proteins were produced in transgenic HRs. The recombinant proteins were extracted from the tobacco HRs and used against Pectobacterium carotovorum, Agrobacterium tumefaciens, Ralstonia solanacearum, and Xanthomonas campestris pathogenic bacteria and Alternaria alternata and Pythium sp. fungi. Two recombinant proteins had a statistically significant (p < 0.01) inhibitory effect on the growth and development of plant pathogens. The CBD-DrsB1 recombinant protein demonstrated a higher antibacterial effect, whereas the DrsB1-CBD recombinant protein demonstrated greater antifungal activity. Scanning electron microscopy images revealed that the structure of the fungal mycelia appeared segmented, adhered to each other, and crushed following the antimicrobial activity of the recombinant proteins. Due to the high antimicrobial activity of the recombinant proteins against plant pathogens, this strategy can be used to generate stable transgenic crop plants resistant to devastating plant pathogens.

Efficient production of antifungal proteins in plants using a new transient expression vector derived from tobacco mosaic virus

Fungi that infect plants, animals or humans pose a serious threat to human health and food security. Antifungal proteins (AFPs) secreted by filamentous fungi are promising biomolecules that could be used to develop new antifungal therapies in medicine and agriculture. They are small highly stable proteins with specific potent activity against fungal pathogens. However, their exploitation requires efficient, sustainable and safe production systems. Here, we report the development of an easy-to-use, open access viral vector based on Tobacco mosaic virus (TMV). This new system allows the fast and efficient assembly of the open reading frames of interest in small intermediate entry plasmids using the Gibson reaction. The manipulated TMV fragments are then transferred to the infectious clone by a second Gibson assembly reaction. Recombinant proteins are produced by agroinoculating plant leaves with the resulting infectious clones. Using this simple viral vector, we have efficiently produced two different AFPs in Nicotiana benthamiana leaves, namely the Aspergillus giganteus AFP and the Penicillium digitatum AfpB. We obtained high protein yields by targeting these bioactive small proteins to the apoplastic space of plant cells. However, when AFPs were targeted to intracellular compartments, we observed toxic effects in the host plants and undetectable levels of protein. We also demonstrate that this production system renders AFPs fully active against target pathogens, and that crude plant extracellular fluids containing the AfpB can protect tomato plants from Botrytis cinerea infection, thus supporting the idea that plants are suitable biofactories to bring these antifungal proteins to the market.

Production of a Recombinant Dermaseptin Peptide in Nicotiana tabacum Hairy Roots with Enhanced Antimicrobial Activity

Expression of strong antimicrobial peptides in plants is of great interest to combat a wide range of plant pathogens. To bring the Dermaseptin B1 (DrsB1) peptide to the intimate contact of the plant pathogens cell wall surface, the DrsB1 encoding sequence was fused to the C-terminal part of the two copies of the chitin-binding domain (CBD) of the Avr4 effector protein and used for Agrobacterium rhizogenes-mediated transformation. The expression of the recombinant protein in the tobacco hairy roots (HRs) was confirmed by molecular analysis. Antimicrobial activity analysis of the recombinant protein purified from the transgenic HRs showed that the (CBD)2-DrsB1 recombinant protein had a significant (p < 0.01) antimicrobial effect on the growth of different fungal and bacterial pathogens. The results of this study indicated that the recombinant protein had a higher antifungal activity against chitin-producing Alternaria alternata than Pythium spp. Scanning electron microscopy images demonstrated that the recombinant protein led to fungal hypha deformation, fragmentation, and agglutination of growing hypha, possibly by dissociating fungal cell wall components. In vitro evidences suggest that the expression of the (CBD)2-DrsB1 recombinant protein in plants by generating transgenic lines is a promising approach to produce disease-resistant plants, resistance to chitin-producing pathogenic fungi.

Enhancing the Secretion of a Glyco-Engineered Anti-CD20 scFv-Fc Antibody in Hairy Root Cultures

Hairy root (HR) cultures represent an attractive platform for the production of heterologous proteins, due to the possibility of secreting the molecule of interest in the culture medium. The main limitation is the low accumulation yields of heterologous proteins. The aim of this study is to enhance the accumulation of a tumor-targeting antibody with a human-compatible glycosylation profile in HR culture medium. To this aim, the authors produce Nicotiana benthamiana HR cultures expressing the red fluorescent protein (RFP) to easily screen for different auxins able to induce heterologous protein secretion in the medium. The hormone 2,4-dichlorophenoxyacetic acid (2,4-D) is found to induce high accumulation levels (334 mg L-1 ) of RFP in the culture medium. The same protocol is used to improve the secretion of the tumor-targeting, CD20-specific 2B8-FcΔXF recombinant antibody from glyco-engineered ΔXTFT N. benthamiana HR cultures. The addition of 2,4-D determine a 28-fold increase of the accumulation of fully functional 2B8-FcΔXF in the culture medium, at levels of ≈16 mg L-1 . Antibody N-glycosylation profiling reveal the prominent occurrence of GnGn structures and low levels of xylose- and fucose-containing counterparts. This result is the first example of the expression of an engineered anti-CD20 antibody with a scFv-Fc format at high levels in HR.

Antimicrobial Peptides: Recent Insights on Biotechnological Interventions and Future Perspectives

With the unprecedented rise of drug-resistant pathogens, particularly antibiotic-resistant bacteria, and no new antibiotics in the pipeline over the last three decades, the issue of antimicrobial resistance has emerged as a critical public health threat. Antimicrobial Peptides (AMP) have garnered interest as a viable solution to this grave issue and are being explored for their potential antimicrobial applications. Given their low bioavailability in nature, tailoring new AMPs or strategizing approaches for increasing the yield of AMPs, therefore, becomes pertinent. The present review focuses on biotechnological interventions directed towards enhanced AMP synthesis and revisits existing genetic engineering and synthetic biology strategies for production of AMPs. This review further underscores the importance and potential applications of advanced gene editing technologies for the synthesis of novel AMPs in future.