Edible Vaccines

EDIBLE VACCINES – NEW APPROACH IN PLANT BIOTECHNOLOGY

MAJORITY of the human population is prone to several infections. It is necessary to produce new vaccines that have economic and other advantages over the existing injectable vaccines.
Recently plants are being used as the alternative vaccine production system because of its several advantages over animal system. They can also be used for harvesting immunoglobulins and antiviral proteins, interferon. The emergence of plant edible vaccines has given the new and dramatic hope for human revolution. The first edible vaccines were produced in tobacco in 1990 in which 0.02 % recombinant protein of the total soluble leaf proteins was found.

Today, several plants based edible vaccines including potato, banana, carrot; tobacco, maize etc are available that are successfully engineered by researcher and scientists. For making edible vaccines against the different pathogens, it is necessary to find out pathogen associated antigenic epitopes or surface antigens. The antigenic epitopes are proteins or peptides that are encoded by genomic sequences. Among the different epitopes, protective one can be selected for vaccine development that provokes antibody response.

The basic methodology includes identification, selection and isolation of desirable genes from the pathogen that encodes the surface antigen proteins. The isolated gene can be then cloned in a suitable vector for gene transfer. The selected vector should possess all the unique characteristics of an ideal vector. The molecular markers present in vectors can be used for screening transformed host cells from untransformed. After integration of desirable gene in host genome, the cells can be checked for cloned gene expressions using ELIZA that ultimately uses antigen specific monoclonal antibodies. The transformed cells with positive cloned gene expressions allow them for propagation using plant tissue culture.

The other way to produce a plant based vaccines is to infect the plants with recombinant virus carrying the desirable antigen that is fused to viral coat protein. The infected plant has been reported to produce the desired fusion protein in a large amount in short span. Genetically engineered plants thus act as biofactories for vaccine production.

ADVANTAGES

1.Edible means of administration and gives excellent safety compared to injection.
2.It generates systemic and mucosal immunity. This is essential to avoid respiratory and digestive tracts infection.
3.Heat stability. Stable at room temperature. No need of refrigeration.
4.Mass production is possible.
5.Reduction in production costs.
6.Plants can be easily reproduced as compared to animals, used as a system for vaccines production.

TRANSGENIC OUTCOMES

Transgenic tobacco is successfully engineered for the production of edible vaccines against Hepatitis B antigen using‘s’ gene of HBV (Hepatitis B Virus). The optimum level of recombinant protein was obtained in leaves and seeds.

Potato is one of the best sources for vaccine production but the raw potatoes are not palatable and cooking destroys protein antigens. Vaccine for cholera is successfully developed in potato.
Banana is the ideal plant for oral vaccine production due to its excellent digestibility, palatability and availability throughout the year. Vaccine for hepatitis B is successfully made in banana.

There are several dramatic outcomes of plant biotechnology still numbers of questions raises related to the ethics and safety of the transgenic products.