Plant-made pharmaceuticals for the prevention and treatment of autoimmune diseases: where are we?

Plant-Produced Vaccines: Future Applications in Aquaculture

Aquaculture has undergone rapid development in the past decades. It provides a large part of high-quality protein food for humans, and thus, a sustainable aquaculture industry is of great importance for the worldwide food supply and economy. Along with the quick expansion of aquaculture, the high fish densities employed in fish farming increase the risks of outbreaks of a variety of aquatic diseases. Such diseases not only cause huge economic losses, but also lead to ecological hazards in terms of pathogen spread to marine ecosystems causing infection of wild fish and polluting the environment. Thus, fish health is essential for the aquaculture industry to be environmentally sustainable and a prerequisite for intensive aquaculture production globally. The wide use of antibiotics and drug residues has caused intensive pollution along with risks for food safety and increasing antimicrobial resistance. Vaccination is the most effective and environmentally friendly approach to battle infectious diseases in aquaculture with minimal ecological impact and is applicable to most species of farmed fish. However, there are only 34 fish vaccines commercially available globally to date, showing the urgent need for further development of fish vaccines to manage fish health and ensure food safety. Plant genetic engineering has been utilized to produce genetically modified crops with desirable characteristics and has also been used for vaccine production, with several advantages including cost-effectiveness, safety when compared with live virus vaccines, and plants being capable of carrying out posttranslational modifications that are similar to naturally occurring systems. So far, plant-derived vaccines, antibodies, and therapeutic proteins have been produced for human and animal health. However, the development of plant-made vaccines for animals, especially fish, is still lagging behind the development of human vaccines. The present review summarizes the development of fish vaccines currently utilized and the suitability of the plant-production platform for fish vaccine and then addresses considerations regarding fish vaccine production in plants. Developing fish vaccines by way of plant biotechnology are significant for the aquaculture industry, fish health management, food safety, and human health.

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.

Edible plants for oral delivery of biopharmaceuticals

Molecular farming is the use of plants for the production of high value recombinant proteins. Over the last 25 years, molecular farming has achieved the inexpensive, scalable and safe production of pharmaceutical proteins using a range of strategies. One of the most promising approaches is the use of edible plant organs expressing biopharmaceuticals for direct oral delivery. This approach has proven to be efficacious in several clinical vaccination and tolerance induction trials as well as multiple preclinical studies for disease prevention. The production of oral biopharmaceuticals in edible plant tissues could revolutionize the pharmaceutical industry by reducing the cost of production systems based on fermentation, and also eliminating expensive downstream purification, cold storage and transportation costs. This review considers the unique features that make plants ideal as platforms for the oral delivery of protein-based therapeutics and describes recent developments in the production of plant derived biopharmaceuticals for oral administration.

Feeding transgenic plants that express a tolerogenic fusion protein effectively protects against arthritis

Although much explored, oral tolerance for treatment of autoimmune diseases still awaits the establishment of novel and effective vectors. We investigated whether the tolerogenic CTA1(R7K)-COL-DD fusion protein can be expressed in edible plants, to induce oral tolerance and protect against arthritis. The fusion protein was recombinantly expressed in Arabidopsis thaliana plants, which were fed to H-2(q) -restricted DBA/1 mice to assess the preventive effect on collagen-induced arthritis (CIA). The treatment resulted in fewer mice exhibiting disease and arthritis scores were significantly reduced. Immune suppression was evident in treated mice, and serum biomarkers for inflammation as well as anticollagen IgG responses were reduced. In spleen and draining lymph nodes, CD4(+) T-cell responses were reduced. Concomitant with a reduced effector T-cell activity with lower IFNγ, IL-13 and IL-17A production, we observed an increase in IL-10 production to recall antigen stimulation in vitro, suggesting reduced Th1, Th2 and Th17 activity subsequent to up-regulated IL-10 and regulatory T-cell (Treg) functions. This study shows that edible plants expressing a tolerogen were effective at stimulating CD4 T-cell tolerance and in protecting against CIA disease. Our study conveys optimism as to the potential of using edible plants for oral treatment of rheumatoid arthritis.

An overview of proteomics approaches applied to biopharmaceuticals and cyclotides research

The evolution in proteomics approaches is notable, including quantitative proteomics and strategies for elucidation of post-translational modifications. Faster and more accurate mass spectrometers as well as cleverer bioinformatics tolls are making the difference in such advancement. Among the wide range of research in plant proteomics, biopharmaceutical production using plants as "biofactories" and the screening of new activities of new molecules, in this case, peptides, are quite important regarding translational proteomics. The present review is focused on "recombinant proteins and bioactive peptides", with biopharmaceuticals and cyclotides chosen as examples. Their application and challenges are focused on a "translational proteomics" point of view, in order to exemplify some new areas of research based on proteomics strategies. This article is part of a Special Issue entitled: Translational Plant Proteomics.

The Escherichia coli-derived thymosin β4 concatemer promotes cell proliferation and healing wound in mice

Thymosin β4 (Tβ4) is one of the most promising thymosins for future clinical applications, and it is anticipated that commercial demand for Tβ4 will increase. In order to develop a new approach to produce recombinant Tβ4, a 168 bp DNA (termed Tβ4) was designed based on the Tβ4 protein sequence and used to express a 4 × Tβ4 concatemer (four tandem copies of Tβ4, termed 4 × Tβ4) together with a histidine tag (6 × His) in E. coli (strain BL21). SDS-PAGE and western blot analysis were used to confirm that a recombinant 4 × Tβ4 protein of the expected size (30.87 kDa) was produced following the induction of the bacterial cultures with isopropyl β-D-thiogalactoside (IPTG). The E. coli-derived 4 × Tβ4 was purified by Ni-NTA resin, and its activities were examined with regard to both stimulating proliferation of the mice spleen cells in vitro and in vivo wound healing. The results demonstrate that these activities of the E. coli-derived recombinant 4 × Tβ4 were similar or even better than existing commercially obtained Tβ4. This production strategy therefore represents a potentially valuable approach for future commercial production of recombinant Tβ4.

A perspective for atherosclerosis vaccination: is there a place for plant-based vaccines?

Alternatives to pharmacological treatments for atherosclerosis are highly desirable in terms of cost and compliance. During the last two decades several vaccination strategies have been reported as an effort to develop immunotherapeutic treatments. This approach consists on eliciting immune responses able to modulate either the atherosclerosis-associated inflammatory processes or the activity of some physiological mechanisms that are up-regulated under this pathologic condition. In particular, the apolipoprotein B100 (ApoB100) and the cholesterilester transferase protein (CETP) have been targeted in these strategies. It is considered that recent progress in the development of experimental models of oral vaccines against atherosclerosis has opened a new avenue in the field: as plant-based vaccines are considered a viable platform for vaccine production and delivery at low costs, they could serve as an oral-delivered therapeutic approach for atherosclerosis in an economical and patient-friendly manner. The rationale of the design, development and evaluation of possible plant-based vaccines against atherosclerosis is discussed in this review. We identify within this approach a significant trend that will positively impact the field of atherosclerosis vaccination.

Expression and subcellular targeting of human complement factor C5a in Nicotiana species

We evaluated transgenic tobacco plants as an alternative to Escherichia coli for the production of recombinant human complement factor 5a (C5a). C5a has not been expressed in plants before and is highly unstable in vivo in its native form, so it was necessary to establish the most suitable subcellular targeting strategy. We used the strong and constitutive CaMV 35S promoter to drive transgene expression and compared three different subcellular compartments. The yields of C5a in the T(0) transgenic plants were low in terms of the proportion of total soluble protein (TSP) when targeted to the apoplast (0.0002% TSP) or endoplasmic reticulum (0.0003% TSP) but was one order of magnitude higher when targeted to the vacuole (0.001% TSP). The yields could be increased by conventional breeding (up to 0.014% TSP in the T₂ generation). C5a accumulated to the same level in seeds and leaves when targeted to the apoplast but was up to 1.7-fold more abundant in the seeds when targeted to the ER or vacuole, although this difference was less striking in the better-performing lines. When yields were calculated as an amount per gram fresh weight of transgenic plant tissue, the vacuole targeting strategy was clearly more efficient in seeds, reaching 35.8 µg C5a per gram of fresh seed weight compared to 10.62 µg C5a per gram fresh weight of leaves. Transient expression of C5aER and C5aVac in N. benthamiana, using MagnICON vectors, reached up to 0.2% and 0.7% of TSP, respectively, but was accompanied by cytotoxic effects and induced leaf senescence. Western blot of the plant extracts revealed a band matching the corresponding glycosylated native protein and the bioassay demonstrated that recombinant C5a was biologically active.

Non-food/feed seeds as biofactories for the high-yield production of recombinant pharmaceuticals

We describe an attractive cloning system for the seed-specific expression of recombinant proteins using three non-food/feed crops. A vector designed for direct subcloning by Gateway® recombination was developed and tested in Arabidopsis, tobacco and petunia plants for the production of a chimeric form (GAD67/65) of the 65 kDa isoform of glutamic acid decarboxylase (GAD65). GAD65 is one of the major human autoantigens involved in type 1 diabetes (T1D). The murine anti-inflammatory cytokine interleukin-10 (IL-10) was expressed with the described system in Arabidopsis and tobacco, whereas proinsulin, another T1D major autoantigen, was expressed in Arabidopsis. The cost-effective production of these proteins in plants could allow the development of T1D prevention strategies based on the induction of immunological tolerance. The best yields were achieved in Arabidopsis seeds, where GAD67/65 reached 7.7% of total soluble protein (TSP), the highest levels ever reported for this protein in plants. IL-10 and proinsulin reached 0.70% and 0.007% of TSP, respectively, consistent with levels previously reported in other plants or tissues. This versatile cloning vector could be suitable for the high-throughput evaluation of expression levels and stability of many valuable and difficult to produce proteins.