Till date there is no cure for AIDS.

Experts have found that the much-publicised 'ABC' of preventive measures -- Abstinence, Being faithful to one's partner and Condoms -- are not hundred per cent satisfactory.

A preventive vaccine -- like the ones already developed for small pox and diphtheria -- seems the only answer to this global threat.

The enemy

Why is modern science yet to find a vaccine for a virus that has only nine genes?

To put things in perspective, the tubercular bacillus has around 3,000 genes.

There are two reasons.

Reason one: The virus is in the process of mutation all the time.

Reason two: The mutation differs from region to region. The HIV virus seen in Indians is different from what you see in the United States or Africa. And because of the ever-changing nature of the virus, the human body cannot produce an antibody to kill it.

Though economic, social and ethical problems have also contributed to scientists not being able to produce a vaccine, the most compelling of all these reasons is scientific.

"We cannot use the live virus," says Dr V D Ramanathan, the man in charge of the AIDS vaccine trial at the Tuberculosis Research Centre in Chennai.

"We tried using a dead virus, but a dead virus does not behave in the same way as a live virus. So, now, the scientific community is trying different approaches. One is to take a part of the genes and put it in a career called vector -- which is a harmless bigger virus -- and inject it in humans."

Why India

Global efforts to invent an AIDS vaccine have been on from the very early 1990s. When it was found that the virus' mutation differs from region to region, it was decided to conduct research in various regions of the world.

Now, simultaneous trials are on in 40 different places.

In collaboration with the International AIDS Vaccine Initiative, the Government of India represented by the National AIDS Control Organisation and the Indian Council of Medical Research came to an agreement to set up the two trials now being funded in India.

The National AIDS Research Institute, Pune, and the Tuberculosis Research Centre, Chennai, are the two battlegrounds of India's war against AIDS.

In Pune, three genes of the HIV virus are being used for the trial. The vaccine has been tested in Belgium and Germany [Images]; now it is being tested in India.

The vaccine under trial in Chennai is designed by an ICMR scientist, Shekhar Chakraborty from Kolkata.

"He has isolated the virus from Indian patients. Another important thing is, he has taken six genes out of the nine from the virus, and put them in a vector called Modified Vaccinia Ancara," says Dr Ramanathan. "The MVA was used as a vector in the smallpox vaccine in countries like Turkey, so, the safety of the vector has been proved," he adds.

Why humans

"Usually what we do is first test the vaccine in a test tube, then tissue culture, and then on small animals," says Dr Ramanathan.

"But the HIV vaccine cannot be tested like that because it doesn't have any effect on animals. Primates like monkeys can get affected but doing primates research is very difficult because many are endangered species. Even if we test on primates, the question arises how much of it can be applicable to human beings. So, it is wiser to have human trials," he adds.

"We have tested (the vaccine) on animals like rabbits and rats to see whether the vaccine harms animals -- because no vaccine can be given just like that to human beings," Dr Ramanathan explains.

The Research Centre has obtained clearances from several organisations like the Scientific Advisory Committee, the Institutional and National Ethics Committee, the Genetic Engineering Approval Committee, and also the health ministry, to conduct human trials.

At an informal level, the Community Advisory Board has also been consulted.

The approvals took a year to get.

The test trials are a joint effort by the Research Centre and a non-governmental organisation called YRG Care, which provides volunteers for the tests.

The trial

There are three phases in the HIV vaccine trial.

The first phase -- done on 30 to 50 healthy, HIV-negative people -- looks primarily at safety. The secondary objective of the test is to see whether it induces an immune response.

In the second phase, it is tested on about 300 people. The primary objective is to double-check the safety of the vaccine, but whether the vaccine produces an immune response in human beings and how much of the vaccine should be used (dose titration) are also tested.

"Those who are identified as high risk group -- like sex workers, drug users, etc -- are not used as volunteers in the first two phases," explains Dr Ramanathan.

In the third phase -- conducted on a group of more than 3,000 people -- half of the volunteers are from the low risk groups, and the rest from the high risk groups.

Dr Ramanathan stresses that the volunteers are told what is at stake. They are told "that what we try is only a vaccine candidate and not a vaccine. So, we tell our volunteers not to indulge in high risk behaviour."

Phase One, which started in January this year, will culminate in February 2008. It will take six more months for the data to be analysed.

Another four years are needed for the Phase Two and Phase Three will take even longer.

So, the trials may take about 20 years.

The volunteers

During the 18 months of Phase One of the trials, the volunteers, whose identity is kept secret, have to visit the Research Centre 17 times; blood is drawn from them 14 times.

For each visit, they are given Rs 500, which amounts to Rs 8,500 over one-and-a-half years.

"This is not a very good sum," agrees Dr Ramanathan. "It is only a compensation and not an incentive. But if any mishap occurs, they will be taken care of by the sponsors. They will also be given a medical insurance for the trial period," he adds.

Initially, the Research Centre and YRG Care spoke about the vaccine trials at various places like corporate offices, colleges, etc. But few people were willing to volunteer.

The Research Centre decided to brief the media in detail.

"What turned the tide was the media workshop and the articles that appeared in newspapers," says Dr Ramanathan.

"More than 300 people came to our centre but after counselling and discussing with their families, 68 came for health screening. As we are testing in two doses, 16 are enrolled and another 16 are now being recruited (for Phase One)."

The volunteers are willing soldiers in the war on AIDS.

"One person came and told us, 'I know Bill Gates [Images] is giving a lot of money for the HIV/AIDS affected. I don't have money to give. That is why I am volunteering myself,'" says Dr Ramanathan.

"Another person told us, 'I am a member of the Blue Cross society and against animal experimentation. That is why I am volunteering myself.' Another person from a lower middle class family refused to accept the Rs 500 given as compensation," he continues.

"The primary motivation appears to be doing something for society. Many have seen people dying of AIDS," Dr Ramanathan adds.

"And, above all, they have understood that by participating in the trial, they are not going to be infected."