Researchers are launching a project to discover how certain people, dubbed “elite controllers”, are successfully able to fend off the HIV virus without using drugs.
More and more cases of such people-also known as “elite suppressors”-are coming to light. Unlike the sex workers in Kenya identified a decade ago as being HIV-negative despite their constant exposure to the virus, elite controllers are infected, and do develop antibodies to the virus, but at a very, very low level. Their immune system is naturally able to suppress the virus and they remain as healthy and symptom-free as people on antiretroviral drugs, despite not receiving this treatment. “We have recruited over 100 elite controllers ourselves and an additional 100 through our collaborators,” says Bruce Walker at the Massachusetts General Hospital in Boston, US. “We are now identifying about 10 a week through word of mouth”, he told New Scientist.Super studyOne of these elite controller patients will be presented at a press conference Walker is holding on Wednesday in Toronto, Canada, at the International AIDS conference. Walker will also be using the event to issue an appeal for 1000 such patients to be identified and included in a single study to discover how they keep the virus in check. “The hope is that if we understand the basis for keeping the virus in check, it could help us develop entirely new treatments,” he says. Walker estimates that elite controllers account for around 1 in 300 cases of HIV. They qualify as elite controllers if they have fewer than 50 virus particles in each millilitre of their blood. “Mucked-up” calculationsBut another study, unveiled in Toronto on Monday by Oliver Laeyendecker of Johns Hopkins University Medical School in Baltimore, US, suggests that numbers of elite controllers could be higher, at around 1% to 2% of all infected individuals. Laeyendecker identified 183 HIV positive individuals during a random HIV screening at the emergency unit at the Johns Hopkins Hospital in Baltimore, Maryland, in 2001. Of that group, further tests revealed three elite controllers. “Their low viral load mimics that of the newly infected even though they are not and so this could muck up our calculations about the rate of infection in the population at large,” says Laeyendecker. The more virus a person carries, the more infectious they become, so the elite controllers are probably less likely to infect people than most HIV carriers, he says. Laeyendecker speculates that the elite controllers owe their immunity either to some genetic predisposition which gives them a stronger immune system, or to infection with a weak strain of HIV which successfully primes the immune system without completely wrecking it. HIV freeThere have been other instances of natural resistance. Ten years ago, it was discovered that some female sex workers in Kenya were completely resistant to the virus. “They seemed to be HIV negative, and had no anti-HIV antibodies in their blood,” says Sarah Rowland-Jones, director of research at the UK Medical Research Council’s Labs in Fajara, Gambia. The women probably fought off the virus with T-cells rather than antibodies, she says. Vaccines designed to stimulate T-cells rather than antibodies to fight the virus are in the mid-stages of testing at the moment, she says.But the elite controllers are different, says Rowland-Jones, because HIV and antibodies are both detectable in their blood, albeit at very low levels. “What’s most interesting is what these people can tell us about how their immune system deals with the virus,” she says.(Source: Massachusett’s General Hospital; John Hopkins University: New Scientist: 15th August 2006).