Search for Aids vaccine turns to brothels

A microbiologist thinks that a group of Kenyan prostitutes could hold the key to defeating Aids. Philip Fine reports.

A mysterious resistance to HIV by a group of Kenyan prostitutes has provided the key to a possible Aids vaccine that is being readied for its first phase of human testing.

A team of researchers, headed by Canadian microbiologist Frank Plummer, has begun to understand why a group of Nairobi women who have been highly exposed to HIV never contracted the virus that leads to Aids.

In sub-Saharan Africa, which is estimated to have 90 per cent of the world's Aids cases, these 30 women who sleep with an average of four men a day - one of whom will statistically test positive - have remained HIV negative for the past 15 years.

"What is unique is that they are so highly exposed, even more so than someone whose partner is HIV positive," said Professor Plummer, who, along with fellow researchers, is going beyond trying to develop a vaccine from the actual virus and attempting to mimic at a cellular level what they have observed in the prostitutes. They have also studied the family of one of the women, Hawa Chelangat, and discovered the resistance to be genetic.

"What we are trying to do is develop a vaccine to promote T-cell response to HIV like we see in Hawa," Professor Plummer said. The team's vaccine is expected to go on the market in 2004, after passing through the various phases of testing.

Professor Plummer did not originally set out to work on an Aids vaccine. In 1981, he came to Kenya as a senior trainee to research a sexually transmitted disease called Shancroid. At the time, Aids was just beginning to be written about, having been observed in Zairians and several Europeans of African origin.

When the number of Aids patients started to grow - especially in Kenya, which now counts one in six hospital patients with Aids-related ailments - the research changed direction.

The focus turned to the Aids virus. A small clinic was opened in Nairobi in 1985 to treat patients and study the disease.

The researchers had already been working with sex workers in a shanty town in the district of Pumwani Majengo. Their colleague Elizabeth Njagi had begun some research and public sex education with the prostitutes.

The team decided to test the women who were selling sex. Of the 600 who came forward, two-thirds tested positive for HIV. Over the next three years, the team tracked the group and discovered a 30 per cent rise in those testing positive. But rates never reached 100 per cent and, despite high exposure, levelled out. What is more, the remaining 5 per cent of the women never acquired HIV.

The research team is now a four-way partnership comprising the universities of Manitoba, Nairobi and Oxford and the International Aids Vaccine Initiative. It has been gaining international exposure, giving more hope for a possible vaccine. There is an increasing number of projects dedicated to Aids vaccine research, and a couple of pharmaceuticals companies, which have traditionally treated vaccines as a poor cousin to drug treatment, are also working on them.

The story of Professor Plummer's work was recounted in a recently released Canadian documentary called Searching for Hawa's Secret. His research will also feature in a BBC series on medical advances.