(9 Aug 1996) English/Nat
American and European scientists believe they have unraveled one of the mysteries of the AIDS epidemic - why some escape infection despite thousands of risky sexual encounters.
The answer for many appears to be genetic.
Findings released today indicate some included in high risk groups, have genes that make it extremely difficult to catch HIV, the AIDS virus,
The discovery of an anti-HIV gene opens new possibilities for treating and preventing the disease.
If scientists can find a way to mimic the effects of this inherited genetic shield, they believe it may be possible to create a drug that will protect people from becoming infected with the AIDS virus.
The breakthrough first came from research in the U-S.
SOUNDBITE:
This was originally discovered because there were several individuals who were studied here in the United states who were exposed quite frequently to the virus and didn't get infected under the circumstances, where you would have expected that the odds were that they would have got infected.
SUPER CAPTION: Dr Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases.
Scientists made the discovery with the help of two gay men who volunteered in New York City.
The men, who said they had watched 40 or 50 of their friends and lovers die of AIDS, wondered why their own high exposure to the virus had not led to infection.
The researchers discovered that both men carried a pair of genes that ward off HIV.
They were even more surprised to learn how common these genes are, with scientists believing that about one in 100 white people have the defective gene.
SOUNDBITE:
The occurrence of the gene is much much less common in black Africans, in Asians and in the United States in African Americans. In other words if you are non-Caucasian of western European background, then the incidence of not only the complete lack of the gene, but even of the partial abnormality is much less than you would see in Caucasians.
SUPER CAPTION: Dr Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases.
The key to warding off HIV is a mutation in the genes that direct the body's defences against disease.
In this case, a gene called CCR5 is missing a chunk of information, so the body fails to produce a particular protein. This protein is one of the docking points the AIDS virus needs to invade cells.
Those who are born with two copies of the mutant gene - one from each parent - appear to be highly resistant to AIDS infection.
Already, there is some concern that people stop using condoms if they learn they have two copies of the mutant gene.
SOUNDBITE:
One of the things that we have to be careful about is that people will then go to get screened to see if they lack this particular receptor, if they have they have the genetic defect and then inappropriately assume that if they do have this genetic defect, therefore it's OK for them to practice non-safe sex. That would be a terrible mistake because we still don't understand the full spectrum of mechanisms of how the virus can infect different types of cells. We have to be really careful that we don't assume something that isn't really true.
SUPER CAPTION: Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases.
Another report scheduled for publication later this month supports the American finding by describing efforts to locate the mutant gene in people of European, African and Asian heritage.
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