For a cause

in st Louis, Missouri, usa , hundreds of healthy people are leasing their bodies to medical research and contributing to the development of a vaccine for aids . They are receiving injections containing canarypox viruses that cause disease in birds but are harmless to humans. After being genetically-engineered, the viruses envelope three extra genes that are normally found only in hiv , the virus that causes aids . In a few weeks time, the bodies of the volunteers who do not have aids will start behaving as if they had the virus. Researchers hope that the introduction of aids -like characteristics to the volunteers' bodies would lead to the creation of antibodies that can fight off a real infection.

The health risks involved are considerable. For one, any experimental vaccine that is effective will leave the volunteers' replete with hiv antibodies. This implies that they would test positive on any aids test in the future whether they have the virus or not. Researchers cannot be sure if the engineered bird virus would not make the volunteers ill. Moreover, as some studies on animals suggest, aids vaccines can sometimes speed up the progression of the disease in people who eventually become infected.

The struggle to develop a vaccine for aids has never been as intense as it is at present. Though some new drugs and therapies have been successful in curbing the disease to an extant, the benefits are only temporary. Also, they are quite expensive and unavailable in developing countries where 95 per cent of new cases of aids are being reported. "We will never end this epidemic unless we have a vaccine,' says Sandra Thurman, chairperson of the White House Office of National aids Policy.

But developing a vaccine has also never seemed more difficult. Researchers have endured so many disappointments in the last few years that it is being viewed as a lost battle. The risks to volunteers are considerable and the testing processes laborious. Also, hiv is like no other virus as it infects the very immune system cells that form the bodies' line of defence

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