AIDS researchers want to expand their study of a rare group of HIV-infected people, whose immune systems naturally and mysteriously prevent the virus thriving in their bodies, to span the globe.

Studies of these elite controllers, which aim to find an AIDS vaccine, have so far concentrated on north America. But now scientists are hoping to draw in people from Asia, Africa and Latin America.

Elite controllers are healthy, have no signs or symptoms of HIV-related disease and no need for treatment, sometimes as much as 10 years after their infection. Scientists are hoping to uncover the secret behind their robust immune systems and use it to design a vaccine for everyone.

The hope is if we know the immune protective mechanism in elite controllers, we can target it for vaccine design, Yu Xu, assistant professor of medicine at Massachusetts General Hospital and Harvard Medical School, told Reuters after addressing an AIDS vaccine conference in Paris.

There are now 2,000 such controllers or long term nonprogressers mostly from the United States and Canada, whose blood samples and other data are being closely studied. Now scientists are hoping to bring in others from China, South Africa, Peru, Thailand, Brazil and other parts of the world.

At the conference, researchers detailed a trial in Thailand that appears to have shown a vaccine can protect some people -- although scientists still do not understand why or how.

Delegates are hoping to piece together a clearer picture of how to design a vaccine that would prevent infection.

DOING IT NATURALLY

An estimated 33 million people globally have HIV, and there is no cure. Drugs can control the virus and people like the controllers, who can do it naturally, are unusual.

There are many in China. There are about 400 -- villagers infected in the 1990s and who are surviving until now. They have very low viral loads, Yu said.

Last year we went to China and contacted some researchers and they may send us samples too, Yu said, adding that collaboration from Hong Kong may also be likely.

We have collaboration with South Africa, Peru, Thailand, Brazil. We hope to get more patients involved. Either we can have samples or transfer some technology.

There are two classes of controllers, the more common being those with 2,000 copies of the virus or fewer in their bodies, and the even rarer elite controllers who have fewer than 50 copies.

(Virus in the) elite controllers can't be detected at all (with regular equipment). On average, an HIV-infected person has 30,000 copies, Yu added.

Yu's colleague Mathias Lichterfeld told a news conference that controllers appear to have superior dendritic cells, one of the many types of immune cells, which appear to be a point of access for the AIDS virus.

Lichterfeld said some of the dendritic cells in the patients have higher activity of certain receptors -- molecular doorways in cells. This offers potentially the opportunity to manipulate these two receptors to advance vaccine studies, he added.

Controllers also appear to have unusually powerful responses to HIV in their CD8 T-cells, another type of immune cell.

How do they maintain the power to respond so fast and effectively? Yu asked.

Thailand China South Africa Canada