Agnes Munyiva has never thought of herself as a lucky woman. Desperately poor, she works as a prostitute out of her home, a tiny tin-roofed hut on the outskirts of Nairobi. To feed her family of five she entertains as many as 10 clients a day on her children's bed, charging the going rate of 25 cents a trick. Her latest boyfriend just landed in jail, and her kids -- forced to play outside in the mud while their mama "has a guest" -- often go hungry on a skimpy diet of corn mash.
Yet in a way, Munyiva is a fortunate woman -- extraordinarily fortunate to be free of HIV, the virus that causes AIDS. Since the disease emerged in Nairobi in the early 1980s, the sexually transmitted virus has infected 90% of the city's lower-class prostitutes; but somehow Munyiva, 42, has avoided the scourge during her 13 years in that grim line of work. "Perhaps God knows that if he takes me away, my children would suffer," she says.
Munyiva is one of a remarkable group of 25 Nairobi prostitutes who are the subjects of intensive scientific study. The fact that they have no symptoms of AIDS is not so amazing, since HIV can lie dormant in the body for many years before it begins its deadly work. What is surprising is that the virus cannot be found in these women at all; it apparently cannot establish itself in their cells.
A small number of people in other high-risk groups, including some homosexuals and spouses of infected hemophiliacs, have shown resistance to infection. But the Nairobi prostitutes, so frequently exposed to the virus for so many years, provide the strongest evidence yet that people can have a natural immunity to AIDS. If the cause of that protection can be identified, it could spur efforts to develop a vaccine.
A team of Kenyan and Canadian researchers has monitored every one of the prostitutes monthly for at least six years. Each of the women has had sex with hundreds, perhaps thousands, of HIV-positive men. There is nothing unusual about the way they go about their business; they don't use condoms more frequently than other prostitutes do, for example. Significantly, they have suffered from other sexually transmitted diseases, including syphilis and gonorrhea.
What keeps HIV at bay? Lead researcher Dr. Francis Plummer of the University of Manitoba thinks the answer may lie in protein molecules called human leukocyte group A antigens. Arrayed along the surface of cells, these molecules help identify foreign invaders such as viruses. Plummer's preliminary research suggests that the HIV-free women have HLAs markedly different from the more typical ones found in Nairobi's other prostitutes. Exactly how these unusual HLAs can repel HIV is a mystery. Other experts are cautious about drawing any conclusions until Plummer's team completes and publishes its research.
There are many precedents for studying people with natural immunity in order to devise vaccines. In fact, the famous vaccine developed by England's Edward Jenner in 1796 resulted from his observation that milkmaids who had gone through bouts of cowpox enjoyed natural protection against the much deadlier smallpox. Plummer hopes his HIV-free prostitutes can play the same role today that Jenner's clear-skinned milkmaids did nearly two centuries ago.
