According to the World Health Organisation (WHO), infectious diseases claim the lives of more than 12 million children under the age of five every year. Vaccine preventable diseases claim the lives of 40,000 adults every year. Diseases like diarrhoea and cholera cause about 10 million deaths per year among children in the developing world. The primary tools in combating these health hazards are vaccines.

Almost all the existing vaccines need to be injected. These vaccines are unaffordable for most of the population in developing and underdeveloped countries because of their high prices. The prices of these vaccines are high due to high costs of production and the need for cold storage. The vaccines could be used more widely, especially in developing countries, if the cost of production is reduced, and if the vaccines could be distributed without refrigeration.

For example, an effective vaccine against cholera is not available in most third world countries because of the expensive bacterial toxic proteins that are necessary for their formulation. Currently, two forms of HBV injectible vaccines are available, both of which are expensive due to their animal protein antigen component. An alternative to these injections are oral vaccines that involve mucosal immunisation. Mucosal or oral vaccines expose the antigen to mucosal surfaces, thereby initiating the immune system of the body to produce specific antibodies against it. Edible vaccines need not be injected. Besides, they are more economical to produce, distribute, store and administer as compared to animal-generated vaccines.

EPV technology

EPV or edible plant vaccine technology makes use of the fact that plant cells allow the entry of special cells designed to detect an unwanted invasion. These special cells are able to provoke an immune response that results in the production of antibodies to fight the harmful antigen. Thus, this technology requires an antigen expression in transgenic plants and can be given by oral delivery. Plants have been transformed by gene encoding the hepatitis B surface antigen (HbsAg), which, when fed to mice, have shown a positive response against the disease. Transgenic potatoes expressing LT-B were also found to induce both serum and secretary antibodies in mice.

Transgenic crops such as banana, potato, tomato, pea, lettuce, alfa-alfa, corn and wheat are considered suitable vehicles for carrying a vaccine with an antigenic component. Edible plant vaccines are believed to be cheaper, can be grown locally, and bypass the need for needles, making them particularly suitable for developing countries. They may one day save lives and lower the cost of protecting people and animals from common killer diseases. The technology will also have immediate value for the production of inexpensive vaccines as food additives for animals. Therefore, there is a great potential for edible vaccines in the global healthcare market.

Research

Edible plant vaccine research currently aims at finding remedies for human diseases with special emphasis on the developing world. In 1997, the United States Food and Drug Administration (FDA) approved the first clinical trial ever of genetically engineered food (potato) to deliver a vaccine.

Dr. Roy Curtiss III, professor of biology at the University of California, and Dr. Guy Cardineau from Mycogen Corporation are the co-inventors of the patented technology for the production and use of transgenic or genetically engineered plants as edible vaccines. The vaccines can be used as protection against a wide variety of infections caused by bacteria, virus, fungi and parasites. Mycogen has been granted exclusive licence to develop edible vaccines and commercial products based on the technology. They hope to begin with edible vaccines in animal feed to protect chickens and pigs from respiratory and intestinal diseases. The technique explores the possibility of controlling food-borne diseases in humans caused by E coli and salmonella bacteria.

More recently, Dr. Curtiss and his team developed genetically modified alfa-alfa, expressing E. coli antigen to control diarrhoeal diseases.

Dr. Joseph Jilka from ProdiGene, a biotechnology company, conducted research on a corn variety that has been genetically programmed to carry a special immune-inducing enterotoxin from E. coli bacteria. It contains viral proteins of a serious pig disease called swine transmissible gastro-enteritis (TGEV). During clinical trials on swines, this transgenic corn proved effective in the prevention of TGEV.