World's Worst Diseases Face New Foe: Biotechnology

[Guest guest]

Friday November 9 1:52 PM ET

World's Worst Diseases Face New Foe: Biotechnology

By

LONDON (Reuters) - Genetic engineering, often slammed by

environmental and consumer groups for its role in altering staple

foods, may have found a niche. It could help save the lives of

millions from the world's most endemic diseases.

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.

And in another use of biotechnology, there is now some realistic hope

that mankind's centuries-old battle against malaria may soon be

nearing its end due to a breakthrough last year in producing the

world's first transgenic mosquito.

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.

``It's a relatively recent technology and I don't know when we would

ever see commercially available vaccines. But it's quite exciting,''

said Mike Steward, immunologist at the London School of Hygiene and

Tropical Medicine (LSHTM).

``It doesn't matter in what plant you insert them (genes) as the

molecular biology principles are identical. The versatility is

amazing,'' he said.

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 (news - web sites).

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.

``One day children may get immunized by munching on foods instead of

enduring shots. More important, food vaccines might save millions who

now die for lack of access to traditional inoculants,'' said leading

journal Scientific American in an article last year on edible

vaccines.

``The advantages would be enormous,'' the article said. ''Nothing

would be more satisfying than to protect the health of many millions

of now defenseless children around the globe.''

Last year, the spotlight fell on hepatitis B, a virus that can cause

high fever, lifelong infection, cirrhosis of the liver and liver

cancer. More than 60% of liver cancers worldwide have been linked to

hepatitis B.

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.

One recent offbeat development was the isolation in a British

laboratory of a nontoxic protein within the venom of a tiny yellow

scorpion that is common in parts of Brazil.

When injected into animals, the protein proved to be a good potential

vaccine as it set up a strong immunity to the venom. But the problem

was that only very limited amounts of the protein could be obtained,

just enough for a handful of people.

Scientists managed to crack the protein's genetic code--and used the

roots of the tobacco plant to purify the homegrown gene into larger

amounts of protein vaccine, with no risk of the scorpion gene getting

out into plant species.

Stings from scorpions, which tend to live in shoes, clothing or bed

linen, or under surface debris such as leaves, represent a

significant medical problem in many of the world's tropical areas.

Mortality rates can be high and thousands die every year.

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 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.''

POLITICS STILL HAMPERS 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.

``Even if we all got all the science right and produced an edible

vaccine...I can't imagine it would be less than 5 or 10 years before

it got through all the hoops,'' said LSHTM's Steward. ``Those are the

scientific and clinical hoops. Then there are the political ones.

``It's pretty low key at the moment. When it was first discussed at

an immunology congress, people were rather amused by the whole thing.

It's still pretty much in its infancy.''