...Agnes has, in effect, a callus: the first time she was exposed to the virus, her body produced enough killer T cells to fight it off. This part isn't unique - the body of every person who is exposed to HIV mounts some level of response, and sometimes manages to fight it off; a single exposure does not guarantee infection. But Agnes's body, it seems, not only produced sufficient and strong enough cells to fight the virus off the first time, it then produced a whole raft of those killer Ts, flooding her system with guardians whose sole brief was to keep an eye out for cells infected with HIV. The infected cells have a distinct pattern of little bumps on them, called epitopes, which act like a red rose in the lapel as far as the killer Ts are concerned, letting them know just which cells they want to hunt down. Then every subsequent time - probably thousands of times - that HIV got into Agnes's body, her killer T cells drove it back. A person does not normally maintain a large number of killer T cells for a long period - just long enough to kill something off, then production drops. But in Agnes, fairly constant exposure to HIV kept her killer T cell count high.
This conclusion was reinforced when Plummer and his team noticed that women who take a 'sex break' - who make a trip home to the village for a few weeks, or save up a little money and leave sex work for a while to try selling shoes instead, or hook up with a regular who keeps them in cash for a year or two - were far more likely to get infected, almost immediately, if they returned to sex work, even though previously they had had years of apparent immunity. On the break, their bodies stopped making the killer T cells, leaving them vulnerable again...
From the moment it became clear that Agnes and a handful of other women in Majengo - about 100 to date - really could fight off the virus, the researchers in Nairobi hoped that their biology would hold the secret of an HIV vaccine. Soon a team from Oxford University was at work on a vaccine that used the epitopes (the tell-tale bumps on infected cells) that triggered Agnes's killer Ts. They hoped it would provoke other people's bodies to produce killer T cells in the same way that the real virus appeared to trigger production in the sex workers. Trials began in Nairobi in 2001, and a second trial was mounted by Pontiano Kaleebu and his colleagues in Entebbe a couple of years later. But despite high hopes, the Oxford vaccine didn't cause that explosion of killer T cells. And so it was back to the painstaking work of trying to figure out the secret of Agnes's immunity. 'Sometimes a vaccine feels impossibly far away,' sighed Keith Fowke. 'All our knowledge about these HIV-resistant people is interesting and I feel it's important... but it is frustrating.'
...
Today, the research strategy in Majengo revolves around intense study of Agnes and the other resistant women (who make up about five per cent of the cohort at any one time), from analysing their genome to breaking down the chemical components of the mucosal membranes in their vaginas, in an effort to figure out what may be protecting them. So far researchers have not found anything present in 100 per cent of the women, so it may be that the protection comes from multiple overlapping factors, including some that are genetic. There is a strong family correlation - people related to an HIV-resistant woman seem to be half as likely to get infected as people who are not related.
Agnes is aware that she is a fascinating specimen. 'Most of the people have been very interested in me,' she said matter-of-factly. But she has no understanding of the biological basis for her HIV resistance. 'No one has told me,' she said with a shrug. She gets good, free health care at the clinic for the occasional sexually transmitted infection and also for respiratory infections which plague residents of the polluted slum. So she is happy to give them her blood a couple of times a year, and to enjoy a sense of contributing something to her community.
But Agnes's survival has served to highlight a disquieting aspect of this research. She has come to the clinic for more than 20 years. In that time, more than $22m in scientific grant money has flowed through the project, and many of the researchers have earned reputations as the top experts in their fields. Yet Agnes and a handful of other women are still selling sex, to an average of eight clients a day, still for a dollar or two each time - although they say they would like nothing more than to get out of sex work. When I asked her what she would like to do instead, Agnes's broad face lit up. 'Any kind of job I could do. I could be a cleaner or anything. But it's very difficult to get a job - you have to know somebody to get a job.' And Agnes said she doesn't know anybody who could help. With only limited literacy after three years of primary school, and no other skills, Agnes said she sees no other options. 'It's embarrassing, this profession,' she said. She refuses to discuss what she does for a living with her children, although she is sure they know. 'I've never told them what I do, but I think they can see it. I think they know what I'm doing is not good but they know I do it to provide for them.'
Agnes's frustration with her life in sex work raises troubling ethical questions about research, the kind that bedevil investigations into Aids vaccines, prevention technologies and treatment, all of which, by definition, involve large groups of poor Africans, the people most at risk. What obligation does a researcher such as Plummer have to the women who have given him their blood for 20 years? What does this project owe Agnes?
...
Agnes's mysterious immune system has garnered her considerable fame in the world of Aids, but little else. She lives a life almost totally unchanged from her first days in umalaya 30 years ago. 'I can buy our daily food out of what I earn, and that's all,' she told me as we sat in the shade of her bustling alley. 'I don't feel famous. It's only that my problems push me to do sex work. If I could find something else, I would.'
The Observer, Sunday May 27, 2007
http://www.guardian.co.uk/aids/story/0,,2089312,00.html
