Experts Study Thriving HIV "Controllers" in Vaccine Search

Studies of "elite controllers," HIV-positive persons whose own immune systems somehow naturally thwart the virus, have so far been concentrated in North America. However, scientists at the AIDS Vaccine 2009 conference now underway in Paris have been told of plans to expand the studies to include controllers in Asia, Africa, and Latin America.

Elite controllers remain healthy, with no signs of HIV-related illness and no need for treatment, for as long as 10 years after infection. Scientists hope that studying them will unlock the secret of their robust immune systems -- knowledge that could one day inform the development of a successful AIDS vaccine.

So far, blood and data from some 2,000 such patients, also known as "long-term nonprogressers," are being closely examined. Most of these subjects are from the United States and Canada.

"There are many [elite controllers] in China," said Yu Xu, assistant professor of medicine at Massachusetts General Hospital and Harvard Medical School, who addressed the Paris conference. "There are about 400 villagers infected in the 1990s and who are surviving until now. They have very low viral loads."

"On average, an HIV-infected person has 30,000 [viral] copies," Yu said. Elite controllers, by contrast, are classified into two groups: those who have a viral count of 2,000 or less, and those whose count is below 50.

At a news conference, Yu's colleague Mathias Lichterfeld said controllers seem to have superior dendritic cells, a type of immune system cell that appears to be an access point for HIV. Some of the patients' dendritic cells show higher activity of certain receptors, or molecular doorways. "This offers potentially the opportunity to manipulate these two receptors to advance vaccine studies," he said, adding that the CD8 T-cells of controllers also seem to have unusually strong responses to HIV.

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