Stable expression of foot-and-mouth disease virus protein VP1 fused with cholera toxin B subunit in the potato (Solanum tuberosum)

The potential of plant-made vaccines to fight picornavirus

INTRODUCTION

Several Picornaviruses are pathogens that generate serious problems for human and animal health worldwide. Vaccination is an attractive approach to fight against picornaviruses. In this regard, the development of low-cost vaccines is a priority to ensure coverage; especially in developing and low-income countries. In this context, plant-made vaccines are a convenient technology since plant cells are low-cost bioreactors capable of producing complex antigens that preserve their antigenic determinants; moreover, they can serve as biocapsules to achieve oral delivery.

AREAS COVERED

In the present review the advances in the development of plant-made vaccines against picornaviruses are summarized and placed in perspective. The main diseases that have been targeted using this approach include Poliovirus, Food and mouth disease virus, Hepatitis A virus, and Enterovirus 71.

EXPERT OPINION

Several vaccine candidates against picornavirus have been characterized at the preclinical level; with many of them capable of inducing humoral and cellular responses that led to neutralization of pathogens when evaluated in vitro and test animal challenge assays. Plant-made vaccines are a promise to fight picornaviruses; especially in the developing world where limited resources hamper vaccination coverage. A critical analysis of the road ahead for this technology is provided.

Artificially designed recombinant protein composed of multiple epitopes of foot-and-mouth disease virus as a vaccine candidate

BACKGROUND

Concerns regarding the safety of inactivated foot-and-mouth disease (FMD) vaccine have been raised since it is produced from cultured live FMD virus (FMDV). To overcome this issue, recombinant protein has been studied as an alternative vaccine.

RESULTS AND CONCLUSION

We designed a chimerical multi-epitope recombinant protein (5BT), which is comprised of tandem repeats of five B cell epitopes (residue of VP1 136-162) derived from different FMDV variants and one T-cell epitope (residue of 3A 21-35). To increase solubility and stability of 5BT, it was conjugated with BmpB, the membrane protein B of Brachyspira hyodysenteriae (B5BT). Our results indicated that 5BT was susceptible to degradation by host protease and produced with substantial fraction of inclusion body. The stability and solubility of 5BT was greatly increased by conjugating to BmpB. FMDV specific antibodies were observed in the serum of mice immunized with 5BT and B5BT comparable to inactivated FMD vaccine. Sera from 5BT and B5BT groups also exhibited high epitope-specific antibody titers in peptide specific ELISA, indicating that all five epitopes are exposed to the B cell receptor for the antibody reaction. Thus the multi-epitope recombinant protein designed in this study may be a potential candidate as an alternative vaccine against FMDV epidemic variants.

Foot-and-mouth disease: overview of motives of disease spread and efficacy of available vaccines

Control and prevention of foot and mouth disease (FMD) by vaccination remains unsatisfactory in endemic countries. Indeed, consistent and new FMD epidemics in previously disease-free countries have precipitated the need for a worldwide control strategy. Outbreaks in vaccinated animals require that a new and safe vaccine be developed against foot and mouth virus (FMDV). FMDV can be eradicated worldwide based on previous scientific information about its spread using existing and modern control strategies.

Recent advances and safety issues of transgenic plant-derived vaccines

Transgenic plant-derived vaccines comprise a new type of bioreactor that combines plant genetic engineering technology with an organism's immunological response. This combination can be considered as a bioreactor that is produced by introducing foreign genes into plants that elicit special immunogenicity when introduced into animals or human beings. In comparison with traditional vaccines, plant vaccines have some significant advantages, such as low cost, greater safety, and greater effectiveness. In a number of recent studies, antigen-specific proteins have been successfully expressed in various plant tissues and have even been tested in animals and human beings. Therefore, edible vaccines of transgenic plants have a bright future. This review begins with a discussion of the immune mechanism and expression systems for transgenic plant vaccines. Then, current advances in different transgenic plant vaccines will be analyzed, including vaccines against pathogenic viruses, bacteria, and eukaryotic parasites. In view of the low expression levels for antigens in plants, high-level expression strategies of foreign protein in transgenic plants are recommended. Finally, the existing safety problems in transgenic plant vaccines were put forward will be discussed along with a number of appropriate solutions that will hopefully lead to future clinical application of edible plant vaccines.

Production of pharmaceutical proteins in solanaceae food crops

The benefits of increased safety and cost-effectiveness make vegetable crops appropriate systems for the production and delivery of pharmaceutical proteins. In particular, Solanaceae edible crops could be inexpensive biofactories for oral vaccines and other pharmaceutical proteins that can be ingested as minimally processed extracts or as partially purified products. The field of crop plant biotechnology is advancing rapidly due to novel developments in genetic and genomic tools being made available today for the scientific community. In this review, we briefly summarize data now available regarding genomic resources for the Solanaceae family. In addition, we describe novel strategies developed for the expression of foreign proteins in vegetable crops and the utilization of these techniques to manufacture pharmaceutical proteins.

Plants as bioreactors: Recent developments and emerging opportunities

In recent years, the use of plants as bioreactors has emerged as an exciting area of research and significant advances have created new opportunities. The driving forces behind the rapid growth of plant bioreactors include low production cost, product safety and easy scale up. As the yield and concentration of a product is crucial for commercial viability, several strategies have been developed to boost up protein expression in transgenic plants. Augmenting tissue-specific transcription, elevating transcript stability, tissue-specific targeting, translation optimization and sub-cellular accumulation are some of the strategies employed. Various kinds of products that are currently being produced in plants include vaccine antigens, medical diagnostics proteins, industrial and pharmaceutical proteins, nutritional supplements like minerals, vitamins, carbohydrates and biopolymers. A large number of plant-derived recombinant proteins have reached advanced clinical trials. A few of these products have already been introduced in the market.

The expression of classical swine fever virus structural protein E2 gene in tobacco chloroplasts for applying chloroplasts as bioreactors

It has been reported that genes encoding antigens of bacterial and viral pathogens can be expressed in plants and are shown to induce protection antibodies. The structural protein E2 of classical swine fever virus (CSFV), which has been shown to carry critical epitopes, has been expressed in different systems. Here, we report the expression of CFSV E2 gene in tobacco chloroplasts. Mice immunized with leaf extracts elicited specific antibodies. This indicated that the expressed E2 proteins had a certain degree of immunogenicity. To our knowledge, this is the first report showing induction of protective antibody in response to classical swine fever virus (CSFV) by immunization with antigen protein E2 expressed in tobacco chloroplasts, which will open a new way to protection from CSFV by plant chloroplasts as bioreactors.