What Inder Verma of the Salk Institute, La Jolla, California, is attempting to do is to harness the multiplicative power of the HIV, after having defanged it, to transform it into an effective vehicle for the transmission of a good gene into the human body.

In other words, deleting the disease-triggering proteins from the HIV's genetic code and filling up the blank with the ``good'' material. This process of knocking out inconvenient genes and replacing them with their pliable peers, according to Verma, is ``one of the great glories of molecular biology.'' For, it's the equivalent of ``turning swords into ploughshares.''

Ever since gene therapy became the hottest new thing in cutting-edge science around 1993,spawning 300 clinical trials across the world, the solution-defying problem has been that of finding an effective delivery mechanism to deploy a good gene to counter afflictions as varied as retinitis pigmentosa (the second most important cause of blindness in the country), blood disorders, cancer, and even cardio-vascular disease.

``It is a case of scientists not being able to find a way to implement a good idea,'' says Verma, who was the keynote speaker at the annual symposium of the Ranbaxy Science Foundation in the Capital. ``The result of each new method that is proposed is like the popularity of a new government -- hopes rise very fast, only to dissipate rapidly.'' The challenge, according to Verma, is to find a delivery mechanism that can transmit the beneficial protein from within the body's building blocks (chromosomes in this case) for an extended period of time.

Verma admits that the idea of putting a virus as deadly as HIV into people may sound absurd, but there's a method in this apparentmadness. Viruses, says Verma, have this innate urge to multiply constantly, and contrary to the reputation they have acquired, have no vested interest in causing disease and death, for if they kill an organism, they die along with it. A millilitre of a virus can multiply into one trillion of these invisible creatures. And considering that a vital organ like the liver has a billion cells, it is possible to transfer good genes to 1,000 people using just a millilitre of HIV!

This quality makes the new delivery vehicle a highly cost-effective option, unlike the futuristic gene gun, even for a less developed nation like India. Verma, incidentally, hopes to start clinical trials late next year among the haemophiliacs of San Diego, California, and if he can replicate the success he has achieved in mice and monkeys, he may just help gene therapy overcome its greatest hurdle.

But why HIV? Verma plumped for it because it belongs to the versatile family of lentiviruses, which have the ability to plant themselves onnon-dividing cells, like the neurons on nerve endings . The idea was to immobilise the virus after planting it in the body, to minimise even the faintest possibility of a risk.