Prostitutes key to Aids vaccine

DURBAN - A study of prostitutes by scientific teams in Oxford and Kenya has resulted in an Aids vaccine that combines DNA and wild animal virus, and which is affordable for Third World countries.

The announcement was made at the World Aids Conference in Durban, South Africa, by Andrew McMichael, a professor of immunology at Oxford University, and his counterpart in Nairobi, Professor Job Bwayo.

Development of the vaccine was inspired by studying a rare group of Kenyan prostitutes who, despite acquiring all manner of sexually transmitted diseases, somehow escaped infection with HIV.

Scientists believe the combination of DNA and wild animal virus will make the vaccine more powerful than the score of similar vaccines developed against Aids, which have shown little impact on the disease.

Professor McMichael said if ethical approval was granted, the first phase of the vaccine trial in Oxford, to test its safety, would be followed by testing on 60 people in Nairobi, starting in October.

"Our chances of successfully developing a vaccine are, I would say, better than 50-50. But the earliest we could expect a vaccine to be ready would be in seven to 10 years."

Crucially, the potential vaccine may be affordable to the Third World, where immune-boosting drugs are scarce because Governments and individuals cannot afford them.

If final ethical approval is given, 18 British volunteers, including Dr Evan Harris, the Liberal Democrat education and health spokesman and MP for Oxford, will be injected next month with the vaccine.

It will be too late for this generation, but it may not be for the next.

The development of the vaccine - 10 other similar projects are underway in the world - is being funded by the International Aids Vaccine Initiative (Iavi), which pays grants to scientists on condition that it retains patent rights to the end product.

The group, which has received more than £14 million ($45.5 million) from the British Government, wants a tiered pricing structure for Aids vaccines that would mean rich countries would have to agree in advance to pay more for them and, in effect, subsidise poor nations.

Almost 20 years of attempts to develop an Aids vaccine have drawn a blank, chiefly because of the virus' bewildering ability to change its shape.

The new vaccine is made from the tiny segment of DNA from the HIV virus that stimulates a response in the T-cells, delivered with the oldest weapon in the vaccine arsenal, the vaccinia virus, that 200 years ago opened the scientific war against smallpox.

It is proven safe, but the first safety trials will, in any case, be on British volunteers.

Professor Bwayo, aged 52, of the University of Nairobi, said: "We began studying sex workers, initially for STDs, in 1982.

"About 10 years ago we started looking at their HIV rates and discovered that of the 60 we followed, 10 per cent consistently never showed signs of the Aids virus. They are the keys to our vaccine."

It appeared that the prostitutes were, in effect, being vaccinated by their exposure to HIV - possibly at low levels - but not infected, and this immune response was protecting them from further infection.

Their T-killer cells were recognising and attacking the virus. The vaccine is designed to produce a similar response in people not exposed to the virus by priming their immune systems to respond more quickly before they are overwhelmed by the infection.

Iavi says less than 2 per cent of the millions the world spends annually on Aids goes to vaccine development.

- INDEPENDENT