Tuesday, 12 June 2012 19:26
A small number of HIV-infected patients have immune systems that are able to keep AIDS at bay by preventing the virus from reproducing for years, and researchers are reporting that they've gained new insight into how that works.
These fortunate patients, known as "elite controllers" or "long-term non-progressors," are quite rare. They've long fascinated scientists who want to understand the secrets lurking inside their immune cells. Researchers trying to develop an AIDS vaccine are especially interested in these special patients.
The key seems to be that certain cells in the immune systems of these people are better able to detect and kill cells that are infected with HIV, the virus that causes AIDS, said study co-author Dr. Bruce Walker, a professor at Harvard School of Public Health.
In essence, he said, they have better "glasses" than the same cells in patients who can't fight off the virus as well. These cells are better able to "see" signs of trouble from infected cells that send out a kind of distress signal.
The new research shows that "there's a way to measure what's good vision and what's bad vision," Walker said. "We can immediately start looking at vaccine candidates to see if our techniques of training these killer cells are leading to really good vision or not. We can also try to understand what it is that's impaired the vision in some of these patients and allowed for good vision to develop in others."
The researchers came to their conclusions after studying the blood of five "elite controllers" and five normal HIV patients.
Only about one in 200 or 300 HIV patients is able to naturally keep the virus from developing into AIDS without the help of medications, Walker noted. One person has been fending off AIDS since 1978.
"We can't be sure that everybody who achieves this state is actually going to persist in it, but it certainly looks like the vast majority of them will," he said.
Nitin Saksena, head of the retroviral genetics division at Westmead Millennium Institute's Center for Virus Research in Sydney, Australia, said the study needs to be confirmed by other research, and it has limitations, such as the small number of patients involved. It's important to consider that "elite controllers" are quite different from each other, Saksena added.
Dr. Mark Connors, chief of the HIV-specific immunity section with the Laboratory of Immunoregulation of the U.S. National Institute of Allergy and Infectious Diseases, questioned the study results, saying they don't demonstrate why the killer immune cells work more effectively in the elite controllers. Essentially, Connors doesn't think the study authors discovered why the cells have better "vision."
Study co-author Walker, however, said the research is valuable: "This is another example of HIV revealing its secrets. Having been in this field for 30 years, the remarkable thing is that we just keep learning more."
The study is published in the June 10 online edition of Nature Immunology.
by Randy Dotinga
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