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Scientists to study genes of small group of HIV patients who don’t get sick

Posted by pozlife on August 17, 2006

Helen Branswell, Canadian Press

Published: Thursday, August 17, 2006

TORONTO (CP) – They are medical mysteries, medical marvels – HIV-positive people who, long after being infected with the virus that causes AIDS, do not progress to illness.

Now an international team of scientists, including several from Canada, plans to study the genetic blueprints of these special HIV survivors trying to puzzle out how their immune systems keep the killer virus in check, without the assistance of the drugs the vast majority of HIV-AIDS patients need to stay alive.

The researchers, including the University of Montreal’s Rafick-Pierre Sekaly, outlined their plan to study a large group of so-called “elite controllers” at a news conference Wednesday at the International AIDS Conference.

“This is trying to find the genetic basis of the disease,” said Dr. Bruce Walker, director of Partners AIDS Research Center at Massachusetts General Hospital and one of the founding members of the study.

The hope is that identifying how the immune systems of these people keep the virus from replicating to dangerous levels will teach researchers how to develop an HIV vaccine – either a standard vaccine given before exposure to prevent infection, or a vaccine given after infection to keep the virus at non-dangerous and non-transmissible levels.

“If you have a vaccine where you are not able to completely prevent infection, but . . . people who are able to control the virus below 2,000, I think you will have achieved a major thing in terms of public health. That’s essentially what we’re hoping at least to do,” Sekaly said.

“We’ll have a signature of an immune response that we can mimic.”

The figure he used refers to the number of viruses in the blood; 2,000 viruses per millilitre of blood is believed to be a virtually non-infectious level. In acute phases of HIV infection, each millilitre of blood can contain between one million and 10 million viruses.

Some of the elite controllers this consortium plans to study are so successful at suppressing the virus naturally that it is undetectable in their blood, meaning their virus count is below 50 copies per millilitre.

The group hopes to enrol about 1,000 elite controllers in their study and needs about 800 more. On average, the study subjects have been infected for about 15 years, said Walker. Most people infected with HIV will need to go on antiretroviral drugs within a decade of becoming infected.

The patient rosters of Canadian AIDS clinicians have produced a number of subjects so far.

“Between the group in Montreal and the group in Vancouver . . . we are able to contribute about 25 of these individuals to the study,” said Sekaly, who added the researchers are tapping into international partnerships in places like Brazil and Kenya to try to recruit additional subjects.

Finding these rare individuals has been difficult, though Walker realized he’d hit upon a good recruitment practice when he spoke awhile back to physicians with AIDS practices. He asked how many had patients who would qualify as elite controllers – about half the doctors put up their hands, he said.

“Everyone who has a large practice has some of these people – and they don’t know what to do with them,” Walker said.

A similar genomic study identified the genes responsible for juvenile macular degeneration, with a subject sample of about 100 people, Walker said. But whether the technique can work for HIV remains to be seen.

“We’ve got to try,” he said. “It’s a critically important study.”

Sekaly suspects the researchers will discover that no one gene is responsible for the protection these individuals have, that multiple genes are at play. “We’ll still be able to reconstruct the system,” Sekaly said.

On the Net:

The Elite Controllers study, http://www.mgh.harvard.edu/aids/hiv-elite-controllers.asp

© The Canadian Press 2006


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