Sex workers in Kenya have provided scientists with the tools to develop a trial vaccine against HIV. David Gough reports from Nairobi
Majengo, a slum area of the Kenyan capital, Nairobi, is a sprawling maze of narrow alleys and paths scored by the open flow of untreated sewage. About 80 000 people live among the detritus of the red-light slum, where a sex worker’s home is marked by an empty stool placed outside the door.
Hadija is 38 years old and has been a sex worker for 17 years. She knows that she is having sex with HIV-infected men, yet refuses to heed the dangers.
Pulling aside a flimsy curtain draped over the entrance to the shack where she lives and works, Hadija says that she has lost count of the number of HIV tests that she has had.
On the floor of the shack, a stretch of tattered linoleum barely covers the mud that seeps through the cracks. A pristine white sheet is spread across the wooden bed.
Hadija says that she has four or five customers every day and apart from the risks of disease she enjoys her job. “Before Aids, I used to have as many as 30 customers per day,” she says, adding that the cost of her services is 30 shillings (about R3).
“Five of my regular customers have died of Aids and some of my friends who shared the same men as me have also died.”
Hadija maintains that she always used condoms but reported to the clinic last week with syphilis. “Only God knows why I don’t have Aids,” she says.
Hadija is one of more than 50 sex workers that British and Kenyan scientists believe have helped unlock the secrets of a possible vaccine for the Aids virus.
Having spent the past 15 years studying HIV in sex worker communities in Majengo and an area of Gambia, scientists from the universities of Nairobi and Oxford discovered more than 50 sex workers who have repeatedly tested negative for HIV, despite continual exposure to the disease.
They have now utilised that knowledge to develop a vaccine designed to combat the strain of Aids prevalent in Africa.
It has already been tested on primates with encouraging results. According to Dr Omu Anzala, a senior laboratory technician with the University of Nairobi team, about 70% of the animals became HIV resistant after being administered the vaccine.
Toxicity trials on humans are due to start in Oxford early next year.
The Majengo HIV study began in 1985 when 60% of the sex workers there tested positive. Five years later the team had identified a group of sex workers who remained negative despite having as many as 30 clients per day.
“Our first priority was to show that these women had indeed been exposed to the virus,” said Dr JJ Bwayo, chair of Nairobi University’s department of medical microbiology. “They were still reporting to the clinic with other sexually transmitted diseases so we knew that it was not because condoms were being used.”
The scientists observed that the women in question had very high levels of killer T- cells – cells which attack the virus – in their body, suggesting that they had indeed been exposed to HIV.
The team also noticed that a high number of long-term non-progressors – women who are HIV positive but have not developed Aids – also had high levels of the killer T-cells.
“This was further evidence that it was the presence of the killer T-cells which was holding the virus at bay,” said Anzala.
Soon after reaching this conclusion, the Nairobi scientists learned that an Oxford University study in Gambia was yielding similar results and leaning towards the same conclusions. “That was when we knew that this was a true phenomenon,” said Anzala.
While ordinary vaccines are designed to stimulate antibodies to disease, this vaccine will induce the production of the T-cells, which the scientists believe to be the key to women like Hadija’s immunity.
If all goes well with the toxicity tests in Oxford, phase two of the programme will begin next year in Nairobi. “Testing first in Oxford gives the study credibility,” said Bwayo, “and we didn’t want to be seen as using Kenyans as guinea pigs.”
Anzala agreed, emphasising the importance of a vaccine in Africa where anti-retro viro drugs are way beyond the economy of most people. “The cheapest Aids drug therapy will cost the patient 50 000 shillings (about R5 000) a month and only 1% of Kenyans can afford that.”
“Drugs are not the way forward for us,” said Anzala. “A vaccine is the only answer.”