WASHINGTON, Sept 26 (AFP) - US researchers announced Thursday they have detected a group of proteins that naturally block HIV from developing into AIDS, a discovery that promises to revolutionize treatment for the deadly disease.
After investigating why it is that in a tiny percentage of HIV-positive people the virus remains at very low levels, a joint team of American and Chinese scientists at the Aaron Diamond AIDS Research Center identified a group of proteins, called alpha-defensins-1, -2, -3.
"This discovery is a major step forward in our understanding of how the body fights HIV," said Linqi Zhang, head of the team.
The discovery, the details of which are to published in Friday's edition of Science Magazine, followed a lead first discovered in 1986.
"By understanding how some people's immune systems are able to control HIV infection, we may be able to develop new treatments that take advantage of this phenomenon," Zhang said.
The group of people, known as long-term non-progressors -- amounting to between one and two percent of HIV-positive people in the United States -- do not develop AIDS despite prolonged infection.
A study of HIV-positive prostitutes in Kenya by University of Manitoba researcher Dr. Francis Plummer, also found that five percent of them had a type of natural immunity to developing AIDS.
Scientists found that the human body's CD8 T cells produced some unidentifiable factors that inhibited HIV replication.
Then, in 1995, researchers found a family of proteins called beta-chemokines that accounted for some of the HIV suppression but was not effective against all the strains of the virus and couldn't fully explain the non-progressor phenomenon.
The ADARC team compared the CD8 T cells in long-term non-progressors with the same cells in HIV patients whose immune systems had begun to fail.
They found the presence of alpha-defensins-1, -2, -3 in people who remained healthy, and a lack of these same proteins in those whose immune systems failed and developed AIDS.
These proteins suppressed all strands of HIV, the study found, and may be developed to suppress HIV in the greater infected population.
"Alpha-defensins are promising as a future addition to the HIV treatment arsenal," said study co-author David Ho, director of the Aaron Diamond AIDS Research Center in New York, adding that researchers were "gratified to have solved this mystery."
"Researchers from ADARC are already pursuing new therapeutic approaches based on the data published today," he added, urging some caution nonetheless for the degree of potential the discovery will have for treatment.
"While we are enthusiastic, we wish to be somewhat cautious about the translation of this discovery," he said, because it was "not entirely clear whether we can take this discovery and turn it into a useful therapy."
Ho said researchers do not fully understand yet the mechanism through which the defensins act on HIV, the virus that causes AIDS.
"We're trying to figure out which part of the defensins molecules confer the activity against HIV and whether we can manipulate the molecules to improve its potency."
To confirm that these three proteins were responsible for controlling the virus, the team artificially stripped the alpha-defensins from the proteins produced by CD8 T cells taken from long-term non-progressors, and found that their HIV-blocking capabilities had been virtually eliminated.
To better judge the potency of the alpha-defensins researchers compared synthesized versions of the proteins made in laboratories with a purified version derived from human cells.
The natural form was at least 10 to 20 times stronger than the synthetic version. ADARC researchers are currently working to improve the potency of the synthetic form.
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