Edible Vaccines From Gm Crops: Current Status and Future Scope

Abstract

The idea of an edible vaccine is coming closer to reality as scientists have found a way to incorporate the protein gene with some antigen in some plants. The major hurdles in the path of an emerging vaccine technology are being overcome. In this context, genetically modified (GM) plants are being investigated for the production of vaccines, antibodies and therapeutic proteins. The development of GM crops to produce drugs and vaccines has received considerable investment and is relatively well advanced. The myth surrounding edible vaccines and 'food as pill' is the difficulty to control their intake and distribution, particularly in developing countries where education levels and literacy may be low. However, this concept suffers from the fact that the potency of this class of vaccines and drugs remains unmasked to the majority of the population, which has to be publicized and campaigned in a scientific manner, to make it realistic and useful for the common man. Creating edible vaccines involves introduction of selected desired genes into plants and then inducing these altered plants to manufacture the encoded proteins. This process is known as "transformation," and the altered plants are called "transgenic plants." Like conventional subunit vaccines, edible vaccines are composed of antigenic proteins and are devoid of pathogenic genes. Thus, they have no way of establishing infection, assuring its safety, especially in immuno-compromised patients. Conventional subunit vaccines are expensive and technology-intensive, need purification, require refrigeration and produce poor mucosal response. In contrast, edible vaccines would enhance compliance, especially in children and because of oral administration, would eliminate the need for trained medical personnel. Their production is highly efficient and can be easily scaled up. If the technology is properly nurtured and given the right direction, it may usher into a new era where we will be asked to take “food” rather than “drugs” when we are ill. This review attempts to discuss the current status and future of this new preventive modality

A review on edible vaccines and their prospects

“…The main reason why rice and maize are attractive as candidate edible vaccines is because they can be stored without refrigeration for a very long period of time. But the disadvantage with cereals is that they take relatively long periods of time and require perfect conditions to grow (21).…”

“…It grows relatively quickly and tastes good, thus having a broader range of consumers. The major disadvantage with tomato is that it spoils rapidly after ripening (21).…”

Omics and Edible Vaccines

“…There are chances of development of allergic reactions to plant protein glycans and other plant antigens, and contamination of plant and plant products by mycotoxins, pesticides, or endogenous metabolites (Doshi et al, 2013). Development of immunotolerance to vaccine peptide or protein, the consistency of dosage from plant to plant, is not similar, stability of vaccine inside the fruit is not known, dosage may be variable from plant to plant, and selection of the best plant is difficult, and certain foods, e.g., potato is not eaten raw and cooking may modify the properties of vaccine contained in it because the exact or required dose/amount of antigen cannot be measured in a plant as in case of syringe while using conventional vaccine.…”

“…To counter this problem, a large number of delivery systems have been developed and modified for presenting nonliving antigen to mucosal surfaces, which will allow these antigens to survive from acid and enzymatic attack from gastrointestinal tract. These include polylactide, polyglycolide, microsphere, liposomes, proteasomes, co-chelates, virus-like particles, and immune-stimulating complexes (Doshi et al, 2013). Even more palatable alternatives to potatoes have been developed, e.g., banana.…”

“…These include techniques such as optimization of the coding sequence of bacterial or viral genes for expression as plant nuclear genes and defining the subcellular components to accumulate the product for optimal quantity and quality. Another method is to improve the immunogenicity of the orally delivered antigens by using mucosal adjuvants (Doshi et al, 2013; www.pharmatutor.org).…”