Genetic engineering, often slammed by environmental and consumer groups for its role in altering staple foods, may have found a indication.

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, including many children in developing countries, have been targeted as candidates for vaccines that can be engineered from plants.

So far, there seems to be no obvious end to the sheer variety of biotechnology's potential applications in the fight against disease. Even the roots of the humble tobacco plant are being used to mass-produce a vaccine against scorpion stings in Brazil, which may eventually be incorporated into fruit.

Genetic modification (GM) involves exchanging or splicing genes of unrelated species that cannot naturally swap with each other. The species can be as different as chalk and cheese.

Scientists have spliced spider venom genes into maize and other food crops as a "natural pesticide" to deter insects and birds from feeding on the plants, and inserted fish antifreeze genes into tomatoes to extend their growing season into winter.

Vaccines in Variety of Common Foods

The first human clinical trial of an edible vaccine took place in 1997 when volunteers ate raw potatoes that were genetically engineered against the common E. coli bacteria.

Since then a whole range of plants, most often vegetables, has come under the bioscientist's knife for adaptation as a possible host for vaccines. Foods under study include bananas, potatoes, tomatoes, lettuce, rice, wheat, soybeans and corn.

Last year, mice were fed with modified potato containing an oral vaccine for hepatitis B that passed through the animals' stomachs without being broken down and stimulated the production of antibodies against the disease.

Scientists now say tomatoes and bananas genetically modified to contain such a vaccine may be able to eradicate the virus.

Clinical trials have been conducted on pigs using an edible vaccine for transmissible gastroenteritis in corn, while work is continuing on a vaccine using tomatoes for RSV, a respiratory virus that can be fatal for infants less than 6 months old.

Hope in Fight Against Malaria?

So far, the most trumpeted success story of biotechnology's use in medicine probably came last year when an Anglo-German team of scientists inserted a foreign marker gene into the mosquito genome, allowing the possibility of genetic alteration.

While recognizing that the breakthrough was not yet a cure for malaria, the team hailed the achievement as their "holy grail" and a major advance in malaria control -- after 15 years of efforts to create the world's first transgenic mosquito.

At the time, the team said it might now be possible to create a mosquito that was stable, safe and physically unable to transmit the malaria-causing parasite, maybe within 6 years.

Now, according to one of the team's leaders, there may be reason to rejoice sooner as the battle against malaria nears its end. This tropical disease is responsible for more than a million deaths every year, mainly among young children in Africa.

"Progress has been incredible in this field and probably it may take less time," said Andrea Crisanti at the Department of Biology at London's Imperial College. "Progress has been very fast during the last year, faster than anticipated.

"More release trials will be carried out on islands where malaria is endemic. If this proves successful, then a different and more sophisticated approach will be undertaken," he said. "The idea is to introduce a mosquito which is then able to breed with indigenous mosquitoes and so spread the resistance gene."

GM Use in Medicine

The world biotech industry is no stranger to controversy and comes under regular attack from environmentalists and concerned consumers, mainly on account of its work in modifying food crops for what its critics see as purely commercial motives.

Although still in their infancy, edible vaccines made by bioengineering are unlikely to avoid this debate and will in any case be subjected to years of rigorous testing before commercial licensing can be granted, experts say.

Reuters London, November 9, 2001