Kenyan Prostitutes’ Immunity to HIV Infection May be Key to Effective Africa-Specific Vaccine
Researchers who have documented and studied HIV immunity in more than 100 Nairobi prostitutes have "concocted the first experimental vaccine expressly intended for Africa," and the initial phases of clinical trials in Kenya show promise, the Washington Post reports. The vaccine prompts the same immunologic response observed "so strikingly" in the immune sex workers: elevated levels of cytotoxic T-lymphocyte cells, or the "killer T-cells" that most effectively fight HIV. The "operating theory" of the prostitutes' immunity is that it is "built up like a callus" over time. T-cell production in the blood increased with their first exposure to HIV, and the next encounter provoked even more T-cells, boosting immunity until the women proved essentially "uninfectable." Researchers noted that when several women left prostitution and then returned to it later, they ended up contracting the virus, an observation that reinforced the theory that continuous exposure kept their T-cell levels high. Frank Plummer, scientific director of Canada's National Microbiology Laboratory and the first recorder of the immunity among Nairobi sex workers, stressed the need for a vaccine to come out of this observed immunity, saying, "I'm all for [AIDS] treatment, but focusing on treatment as the solution is not going to solve this" disease. Oxford University researcher Andrew McMichael and his team began developing a vaccine that appears to boost the production of T-cells in the same way that HIV would boost cell production in the prostitutes, and studies of blood taken from the 18 Kenyans who received the vaccine show "an 80 to 90% indication that it actually presents an immune response." But McMichael pointed out that while the vaccine will make it more difficult to become infected, it will not provide "absolute insurance against the virus" (Vick, Washington Post, 5/11). To read the entire feature, click here.This is part of the KHN Morning Briefing, a summary of health policy coverage from major news organizations. Sign up for an email subscription.