High accumulation in tobacco seeds of hemagglutinin antigen from avian (H5N1) influenza

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.

Seed-Based System for Cost-Effective Production of Vaccine Against Chronic Respiratory Disease in Chickens

The production of vaccines in plant cells, termed plant-made pharmaceuticals or molecular farming, is a promising technology for scalable production. Compared to mammalian cell lines, like Chinese Hamster Ovary (CHO) or bacterial cells, plants can be grown with less cost on a large scale to make vaccines antigens and therapeutics affordable and accessible worldwide. An innovative application of this alternative system is the production of vaccines in edible tissues that can be consumed orally to deliver protein antigen without any further processing. In this project, we report stable expression of amino acid sequences corresponding to the TM-1 gene of Mycoplasma gallisepticum as a candidate vaccine antigen against Chronic Respiratory Disease (CRD) in chickens using wheat seed's tissues as a production host. Molecular and immunoblotting analysis confirmed the ubiquitous expression of a recombinant 41.8-kDa protein with an expression level of 1.03 mg/g dry weight in the endosperm tissues. When orally delivered, the plant-made vaccine was effective in terms of developing antibody response in animal model i.e., chicken without any detectable weight loss. Two doses of orally delivered plant-made TM-1 vaccine candidate elicited the immune response and protective effect against MG virus challenge at the level comparable to commercially available inactivated vaccine against CRD. Our study demonstrates that plant-made vaccines are not only safe but also scalable and cost-effective with prolonged stability at room temperature.

Seed- and leaf-based expression of FGF21-transferrin fusion proteins for oral delivery and treatment of non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a global disease with no effective medication. The fibroblast growth factor 21 (FGF21) can reverse this liver dysfunction, but requires targeted delivery to the liver, which can be achieved via oral administration. Therefore, we fused FGF21 to transferrin (Tf) via a furin cleavage site (F), to promote uptake from the intestine into the portal vein, yielding FGF21-F-Tf, and established its production in both seeds and leaves of commercial Nicotiana tabacum cultivars, compared their expression profile and tested the bioavailability and bioactivity in feeding studies. Since biopharmaceuticals need to be produced in a contained environment, e.g., greenhouses in case of plants, the seed production was increased in this setting from 239 to 380 g m^-2 a^-1 seed mass with costs of 1.64 € g^-1 by side branch induction, whereas leaves yielded 8,193 g m^-2 a^-1 leave mass at 0.19 € g^-1. FGF21-F-Tf expression in transgenic seeds and leaves yielded 6.7 and 5.6 mg kg^-1 intact fusion protein, but also 4.5 and 2.3 mg kg^-1 additional Tf degradation products. Removing the furin site and introducing the liver-targeting peptide PLUS doubled accumulation of intact FGF21-transferrin fusion protein when transiently expressed in Nicotiana benthamiana from 0.8 to 1.6 mg kg^-1, whereas truncation of transferrin (nTf338) and reversing the order of FGF21 and nTf338 increased the accumulation to 2.1 mg kg^-1 and decreased the degradation products to 7% for nTf338-FGF21-PLUS. Application of partially purified nTf338-FGF21-PLUS to FGF21^-/- mice by oral gavage proved its transfer from the intestine into the blood circulation and acutely affected hepatic mRNA expression. Hence, the medication of NASH via oral delivery of nTf338-FGF21-PLUS containing plants seems possible.

Development of Plant-Based Vaccines for Prevention of Avian Influenza and Newcastle Disease in Poultry

Viral diseases, including avian influenza (AI) and Newcastle disease (ND), are an important cause of morbidity and mortality in poultry, resulting in significant economic losses. Despite the availability of commercial vaccines for the major viral diseases of poultry, these diseases continue to pose a significant risk to global food security. There are multiple factors for this: vaccine costs may be prohibitive, cold chain storage for attenuated live-virus vaccines may not be achievable, and commercial vaccines may protect poorly against local emerging strains. The development of transient gene expression systems in plants provides a versatile and robust tool to generate a high yield of recombinant proteins with superior speed while managing to achieve cost-efficient production. Plant-derived vaccines offer good stability and safety these include both subunit and virus-like particle (VLP) vaccines. VLPs offer potential benefits compared to currently available traditional vaccines, including significant reductions in virus shedding and the ability to differentiate between infected and vaccinated birds (DIVA). This review discusses the current state of plant-based vaccines for prevention of the AI and ND in poultry, challenges in their development, and potential for expanding their use in low- and middle-income countries.

Strategies for enhancing immunity against avian influenza virus in chickens: A review

Poultry infection with avian influenza viruses (AIV) is a continuous source of concern for poultry production and human health. Uncontrolled infection and transmission of AIV in poultry increases the potential for viral mutation and reassortment, possibly resulting in the emergence of zoonotic viruses. To this end, implementing strategies to disrupt the transmission of AIVs in poultry, including a wide array of traditional and novel methods, is much needed. Vaccination of poultry is a targeted approach to reduce clinical signs and shedding in infected birds. Strategies aimed at enhancing the effectiveness of AIV vaccines are multi-pronged and include methods directed towards eliciting immune responses in poultry. Strategies include producing vaccines of greater immunogenicity via vaccine type and adjuvant application and increasing bird responsiveness to vaccines by modification of the gastrointestinal tract (GIT) microbiome and dietary interventions. This review provides an in-depth discussion of recent findings surrounding novel AIV vaccines for poultry, including reverse genetics vaccines, vectors, protein vaccines and virus like particles, highlighting their experimental efficacy among other factors such as safety and potential for use in the field. In addition to the type of vaccine employed, vaccine adjuvants also provide an effective way to enhance AIV vaccine efficacy, therefore, research on different types of vaccine adjuvants and vaccine adjuvant delivery strategies is discussed. Finally, the poultry gastrointestinal microbiome is emerging as an important factor in the effectiveness of prophylactic treatments. In this regard, current findings on the effects of the chicken GIT microbiome on AIV vaccine efficacy are summarized here.

Plant-Derived Recombinant Vaccines against Zoonotic Viruses

Emerging and re-emerging zoonotic diseases cause serious illness with billions of cases, and millions of deaths. The most effective way to restrict the spread of zoonotic viruses among humans and animals and prevent disease is vaccination. Recombinant proteins produced in plants offer an alternative approach for the development of safe, effective, inexpensive candidate vaccines. Current strategies are focused on the production of highly immunogenic structural proteins, which mimic the organizations of the native virion but lack the viral genetic material. These include chimeric viral peptides, subunit virus proteins, and virus-like particles (VLPs). The latter, with their ability to self-assemble and thus resemble the form of virus particles, are gaining traction among plant-based candidate vaccines against many infectious diseases. In this review, we summarized the main zoonotic diseases and followed the progress in using plant expression systems for the production of recombinant proteins and VLPs used in the development of plant-based vaccines against zoonotic viruses.

Integrating plant molecular farming and materials research for next-generation vaccines

Biologics - medications derived from a biological source - are increasingly used as pharmaceuticals, for example, as vaccines. Biologics are usually produced in bacterial, mammalian or insect cells. Alternatively, plant molecular farming, that is, the manufacture of biologics in plant cells, transgenic plants and algae, offers a cheaper and easily adaptable strategy for the production of biologics, in particular, in low-resource settings. In this Review, we discuss current vaccination challenges, such as cold chain requirements, and highlight how plant molecular farming in combination with advanced materials can be applied to address these challenges. The production of plant viruses and virus-based nanotechnologies in plants enables low-cost and regional fabrication of thermostable vaccines. We also highlight key new vaccine delivery technologies, including microneedle patches and material platforms for intranasal and oral delivery. Finally, we provide an outlook of future possibilities for plant molecular farming of next-generation vaccines and biologics.

Integrating plant molecular farming and materials research for next-generation vaccines

Biologics - medications derived from a biological source - are increasingly used as pharmaceuticals, for example, as vaccines. Biologics are usually produced in bacterial, mammalian or insect cells. Alternatively, plant molecular farming, that is, the manufacture of biologics in plant cells, transgenic plants and algae, offers a cheaper and easily adaptable strategy for the production of biologics, in particular, in low-resource settings. In this Review, we discuss current vaccination challenges, such as cold chain requirements, and highlight how plant molecular farming in combination with advanced materials can be applied to address these challenges. The production of plant viruses and virus-based nanotechnologies in plants enables low-cost and regional fabrication of thermostable vaccines. We also highlight key new vaccine delivery technologies, including microneedle patches and material platforms for intranasal and oral delivery. Finally, we provide an outlook of future possibilities for plant molecular farming of next-generation vaccines and biologics.

Contributions of the international plant science community to the fight against human infectious diseases - part 1: epidemic and pandemic diseases

Infectious diseases, also known as transmissible or communicable diseases, are caused by pathogens or parasites that spread in communities by direct contact with infected individuals or contaminated materials, through droplets and aerosols, or via vectors such as insects. Such diseases cause ˜17% of all human deaths and their management and control places an immense burden on healthcare systems worldwide. Traditional approaches for the prevention and control of infectious diseases include vaccination programmes, hygiene measures and drugs that suppress the pathogen, treat the disease symptoms or attenuate aggressive reactions of the host immune system. The provision of vaccines and biologic drugs such as antibodies is hampered by the high cost and limited scalability of traditional manufacturing platforms based on microbial and animal cells, particularly in developing countries where infectious diseases are prevalent and poorly controlled. Molecular farming, which uses plants for protein expression, is a promising strategy to address the drawbacks of current manufacturing platforms. In this review article, we consider the potential of molecular farming to address healthcare demands for the most prevalent and important epidemic and pandemic diseases, focussing on recent outbreaks of high-mortality coronavirus infections and diseases that disproportionately affect the developing world.

Producing Vaccines against Enveloped Viruses in Plants: Making the Impossible, Difficult

The past 30 years have seen the growth of plant molecular farming as an approach to the production of recombinant proteins for pharmaceutical and biotechnological uses. Much of this effort has focused on producing vaccine candidates against viral diseases, including those caused by enveloped viruses. These represent a particular challenge given the difficulties associated with expressing and purifying membrane-bound proteins and achieving correct assembly. Despite this, there have been notable successes both from a biochemical and a clinical perspective, with a number of clinical trials showing great promise. This review will explore the history and current status of plant-produced vaccine candidates against enveloped viruses to date, with a particular focus on virus-like particles (VLPs), which mimic authentic virus structures but do not contain infectious genetic material.

Genetically-engineered plants yield an orally immunogenic PirA-like toxin from Vibrio parahaemolyticus

Vibrio parahaemolyticus is the main etiological agent of human gastroenteritis by seafood consumption and some strains from this species causing the Acute Hepatopancreatic Necrosis Disease in shrimp have been recently reported. The PirA-like toxin from V. parahaemolyticus (ToxA) has been recently reported as an attractive antigen implicated in subunit vaccine development. Since plants are attractive hosts for the production and delivery of vaccines in the present study plants expressing ToxA were developed to account with a low cost platform for the production and oral delivery of ToxA. Tobacco plants were genetically engineered by Agrobacterium-mediated transformation to stably integrate the ToxA-coding gene into the nuclear genome. Transgenic lines were rescued in kanamycin-containing medium and analyzed by ELISA to determine ToxA yields observing levels up to 9 μg g-1 FW leaf tissues. Western blot analysis confirmed the presence of the ToxA protein in plant extracts. Immunogenicity assessment of the plant-made ToxA was performed in mice, comprising a 4-dose oral immunization scheme; revealing the induction of anti-ToxA humoral responses (IgG in serum and IgA in feces). This study opens the path for the development of low cost plant-based vaccines against Vibrio parahaemolyticus.