A banana or a syringe: journey to edible vaccines

A four-week study on the toxicity of repeated intramuscular administration of plant-based BA-CoV2-0301 vaccine against SARS-CoV-2 in Sprague-Dawley rats

In December 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified in Wuhan, China, leading to the global Coronavirus Disease pandemic. The rapid spread of SARS-CoV-2 highlighted the urgent need for effective vaccines. However, the high cost, cold storage requirements, and scalability challenges associated with mRNA vaccines have necessitated alternative vaccine technologies. In the study, the safety of a plant-based vaccine was evaluated. The vaccine, an emulsion of the SARS-CoV-2 S1 antigen and a synthetic TLR4 agonist produced and purified from Nicotiana benthamiana, was administered to Sprague-Dawley rats three times over 4 wk. Mortality, clinical signs, body weight, food consumption, vision, urinalysis, gross findings, organ weight, hematology, serum biochemistry, histopathology, and immunogenicity were evaluated. The results showed that antibodies were efficiently produced and maintained for one month following vaccination with the plant-derived receptor-binding domain (RBD) antigen of COVID-19. Furthermore, the rats showed no toxicological symptoms, with reversible changes at the injection site and minor histological alterations in the spinal cord and bone marrow, typical of vaccine responses. The plant-derived SARS-CoV-2 vaccine appears safe following repeated administration over 4 wk and represents a promising alternative for potential use in human clinical trials and clinical applications.

The recent advancements in protein nanoparticles for immunotherapy

In recent years, the advancement of nanoparticle-based immunotherapy has introduced an innovative strategy for combatting diseases. Compared with other types of nanoparticles, protein nanoparticles have obtained substantial attention owing to their remarkable biocompatibility, biodegradability, ease of modification, and finely designed spatial structures. Nature provides several protein nanoparticle platforms, including viral capsids, ferritin, and albumin, which hold significant potential for disease treatment. These naturally occurring protein nanoparticles not only serve as effective drug delivery platforms but also augment antigen delivery and targeting capabilities through techniques like genetic modification and covalent conjugation. Motivated by nature's originality and driven by progress in computational methodologies, scientists have crafted numerous protein nanoparticles with intricate assembly structures, showing significant potential in the development of multivalent vaccines. Consequently, both naturally occurring and de novo designed protein nanoparticles are anticipated to enhance the effectiveness of immunotherapy. This review consolidates the advancements in protein nanoparticles for immunotherapy across diseases including cancer and other diseases like influenza, pneumonia, and hepatitis.

Emerging trends of edible vaccine therapy for combating human diseases especially COVID ‐19: Pros, cons, and future challenges

The researchers are still doing efforts to develop an effective, reliable, and easily accessible vaccine candidate to protect against COVID‐19. As of the August 2020, nearly 30 conventional vaccines have been emerged in clinical trials, and more than 200 vaccines are in various development stages. Nowadays, plants are also considered as a potential source for the production of monoclonal antibodies, vaccines, drugs, immunomodulatory proteins, as well as used as bioreactors or factories for their bulk production. The scientific evidences enlighten that plants are the rich source of oral vaccines, which can be given either by eating the edible parts of plants and/or by oral administration of highly refined proteins. The use of plant‐based edible vaccines is an emerging trend as it possesses minimum or no side effects compared with synthetic vaccines. This review article gives insights into different types of vaccines, the use of edible vaccines, advantages of edible vaccines over conventional vaccines, and mechanism of action of edible vaccines. This review article also focuses on the applications of edible vaccines in wide‐range of human diseases especially against COVID‐19 with emphasis on future perspectives of the use of edible vaccines.

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.

Insight of oral vaccines as an alternative approach to health and disease management: An innovative intuition and challenges

Vaccination is the most suitable and persuasive healthcare program for the prohibition of various deadly diseases. However, the higher production cost and purification strategies are out of reach for the developing nations. In this scenario, development of edible vaccine turns out to be the most promising alternative for remodeling the pharmaceutical industry with reduced production and purification costs. Generally, oral route of vaccination is mostly preferred due to its safety, compliance, low manufacturing cost and most importantly the ability to induce immunity in both systemic and mucosal sites. Genetically modified microorganisms and plants could efficiently be used as vehicles for edible vaccines. Edible vaccines are supposed to reduce the risk associated with traditional vaccines. Currently, oral vaccines are available in the market for several viral and bacterial diseases like cholera, hepatitis B, malaria, rabies etc. Herein, the review focuses on the breakthrough events in the area of edible vaccines associated with dietary microbes and plants for better control over diseases.

Engineering of Plants for Efficient Production of Therapeutics

Plants are becoming useful platforms for recombinant protein production at present time. With the advancement of efficient molecular tools of genomics, proteomics, plants are now being used as a biofactory for production of different life saving therapeutics. Plant-based biofactory is an established production system with the benefits of cost-effectiveness, high scalability, rapid production, enabling post-translational modification, and being devoid of harmful pathogens contamination. This review introduces the main challenges faced by plant expression system: post-translational modifications, protein stability, biosafety concern and regulation. It also summarizes essential factors to be considered in engineering plants, including plant expression system, promoter, post-translational modification, codon optimization, and fusion tags, protein stabilization and purification, subcellular targeting, and making vaccines in an edible way. This review will be beneficial and informative to scholars and readers in the field of plant biotechnology.

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.

Vaccine and antibody production in plants: developments and computational tools

Plants as bioreactors have been widely used to express efficient vaccine antigens against viral, bacterial and protozoan infections. To date, many different plant-based expression systems have been analyzed, with a growing preference for transient expression systems. Antibody expression in diverse plant species for therapeutic applications is well known, and this review provides an overview of various aspects of plant-based biopharmaceutical production. Here, we highlight conventional and gene expression technologies in plants along with some illustrative examples. In addition, the portfolio of products that are being produced and how they relate to the success of this field are discussed. Stable and transient gene expression in plants, agrofiltration and virus infection vectors are also reviewed. Further, the present report draws attention to antibody epitope prediction using computational tools, one of the crucial steps of vaccine design. Finally, regulatory issues, biosafety and public perception of this technology are also discussed.

Oral immunization with a plant-derived chimeric protein in mice: Toward the development of a multipotent edible vaccine against E. coli O157: H7 and ETEC

The most bacterial cause of infectious diseases associated with diarrhea are enterotoxigenic and enterohemorrhagic Escherichia coli (ETEC and EHEC, respectively). These strains use colonization factors for the attachment to the human intestinal mucosa, followed by enterotoxins production that could induce more host damage. The Heat-labile enterotoxin (LT) and colonization factors (CFs) are momentous factors for the pathogenesis of ETEC. Also, Intimin and Shiga like toxin (STX) are the main pathogenic factors expressed by EHEC. Because of mucosal surfaces are the major entry site for these pathogens, oral immunization with providing the protective secretary IgA antibody (sIgA) responses in the mucosa, could prevent the bacterial adherence to the intestine. In this study oral immunogenicity of a synthetic recombinant protein containing StxB, Intimin, CfaB and LtB (SICL) was investigated. For specific expression in canola seeds, the optimized gene was cloned in to plant expression vector containing the Fatty Acid Elongase (FAE) promoter. The evaluation of the expression level in canola seeds was approximately 0.4% of total soluble protein (TSP). Following to oral immunization of mice, serum IgG and fecal IgA antibody responses induced. Caco-2 cell binding assay with ETEC shows that the sera from immunized mice could neutralize the attachment properties of toxigenic E. coli. The reduction of bacterial shedding after the challenge of immunized mice with E. coli O157:H7 was significant. The sera from immunized mice in the rabbit ileal loop experiment exhibited a significant decrease in the fluid accumulation compared to the control. The results indicate efficacy of the recombinant chimeric protein SICL in transgenic canola seed as an effective immunogen, which elicits both systemic and mucosal immune responses as well as protection against EHEC and ETEC adherence and toxicity.

Plant-Based Vaccines: Production and Challenges

Plant-based vaccine technologies involve the integration of the desired genes encoding the antigen protein for specific disease into the genome of plant tissues by various methods. Agrobacterium-mediated gene transfer and transformation via genetically modified plant virus are the common methods that have been used to produce effective vaccines. Nevertheless, with the advancement of science and technology, new approaches have been developed to increase the efficiency of former methods such as biolistic, electroporation, agroinfiltration, sonication, and polyethylene glycol treatment. Even though plant-based vaccines provide many benefits to the vaccine industry, there are still challenges that limit the rate of successful production of these third-generation vaccines. Even with all the limitations, continuous efforts are still ongoing in order to produce efficient vaccine for many human and animals related diseases owing to its great potentials. This paper reviews the existing conventional methods as well as the development efforts by researchers in order to improve the production of plant-based vaccines. Several challenges encountered during and after the production process were also discussed.

The search for a promising cell factory system for production of edible vaccine

Despite worldwide vaccination against devastating diseases for decades, millions of children in remote and impoverished regions of the globe die every year from vaccine-preventable infectious diseases. The reasons for incomplete coverage of vaccination programs are based in part on the relatively high costs of conventional vaccinations, including mass production, refrigeration, transportation, and training as well as funding personnel for their administration. Plant-based edible vaccines (PEVs) have been introduced as a revolutionary cost-effective vaccination modality. However, they suffer from major deficiencies that have restricted their application to bench-scale. This article discusses the deficiencies of PEVs and also provides concise overview on the health-promoting, biological and biotechnological features of spirulina (Arthrospira). In short, we envision that spirulina could be considered as a potential alternative biofactory system to the plants toward the production of edible vaccines in high-yield with low-costs that other hosts cannot yet offer.

Paradoxical EU agricultural policies on genetically engineered crops

European Union (EU) agricultural policy has been developed in the pursuit of laudable goals such as a competitive economy and regulatory harmony across the union. However, what has emerged is a fragmented, contradictory, and unworkable legislative framework that threatens economic disaster. In this review, we present case studies highlighting differences in the regulations applied to foods grown in EU countries and identical imported products, which show that the EU is undermining its own competitiveness in the agricultural sector, damaging both the EU and its humanitarian activities in the developing world. We recommend the adoption of rational, science-based principles for the harmonization of agricultural policies to prevent economic decline and lower standards of living across the continent.