Vaccines in Food

One of the major areas of research in biotechnology today is food vaccines that could save millions who now die for lack of access to traditional inoculants.

By using biotechnology to incorporate useful genes into an almost limitless variety of common plants, from rapeseed and tobacco to potato, tomato and banana, scientists aim to produce cheap and stable vaccines in an edible form - and beat disease.

Scourges such as cholera, tuberculosis and hepatitis, all responsible for the deaths of millions every year have been targeted as candidates for vaccines, which can be engineered from plants.

An Indian scientist, Dr. Yasmin Thanavala, currently working in the US, recently reported that potatoes, genetically engineered to express a hepatitis B surface antigen, had successfully protected mice against the disease. The study reported to the National Academy of Sciences, USA, supported the idea of "edible vaccines" for global immunisation against hepatitis B.

Most vaccines are made of proteins that are destroyed in the human gut, and so must be delivered directly into the blood stream through injection. Traditional vaccinations required needles, sterilisation equipment and refrigeration, which are prohibitively expensive in many countries, if available at all.

Edible or food vaccines work differently. Due to the rigidity of plant cell walls, which resist immediate digestion by stomach acids, and degradative enzymes antigenes are slowly freed from plant tissues when digested and released relatively intact into the small intestine. Here secretory antibodies are generated and, after a series of reactions, the immune system is ready to protect the body against any further infection by the organism.

The advantage of this system is that the plants could be grown locally, and cheaply. Because many food plants can be regenerated readily, the crops could potentially be produced indefinitely, without the growers having to purchase more seeds or plants year after year.

Home-grown vaccines would also avoid the logistical and economic problems posed by having to transport traditional vaccines over long distances, keeping them cold enroute and at their destination. And, being edible, the vaccines would require no syringes, which, aside from the cost factor, can lead to infections.

Little would Edward Jenner have dreamt 212 years ago when he first vaccinated his own one-and-a-half year old son, with cowpox against small-pox, that vaccine could be delivered through food. The word "vaccination," the Jenner invented for his treatment (from the Latin vacca for cow), was adopted by Pasteur for immunization against any disease Perhaps it is time to coin a new word for edible vaccines!

Source : AIBA, (BIOTECHNOLOGY GLOBAL UPDATE, DECEMBER 2001, Vol. 3)