World's worst diseases face new foe: biotechnology

[Guest guest]

World's worst diseases face new foe: biotechnology

 

By Jeremy Smith

 

LONDON (Reuters) - Genetic engineering, often slammed by

environmental

and consumer groups for its role in altering staple foods, may have

found a niche where it can 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

which 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, and 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 FIND NEW HOME IN VARIETY OF COMMON FOODS

 

The first human clinical trial of an edible vaccine took place in

1997

when volunteers ate raw potatoes which 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.

 

" 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 innoculants, " 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 which can cause

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

cancer.

More than 60 percent of liver cancers worldwide have been linked to

hepatitis B.

 

Mice were fed with modified potato, containing an oral vaccine for

hepatitis B which 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 which can be

fatal

for infants less than six months old.

 

One recent offbeat development was the isolation in a British

laboratory

of a non-toxic protein within the venom of a tiny yellow scorpion

which

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 home-grown 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.

 

LIGHT AT END OF TUNNEL 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 six years.

 

Now, according to one of the team's leaders, there may be reason to

rejoice sooner as the battle nears its end against malaria, a

tropical

disease 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'S USE IN MEDICINE STILL HAMPERED BY POLITICS, CRITICS

 

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 which are man-made

using 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 five 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. "

 

10:01 11-13-01