1% of Caucasians found to be immune to HIV 2 mutant genes believed to bar AIDS virus from body cells, study finds

September 27, 1996|By Jonathan Bor | Jonathan Bor,SUN STAFF

Adding to a recent surge of AIDS discoveries, scientists are reporting today that a small portion of the Caucasian population is genetically protected from becoming infected with the virus that causes the disease.

Scientists did not find this protection among any of the blacks they studied, suggesting that the genetic trait has traveled mainly among whites.

"This opens up a whole new avenue for designing both diagnostics and therapies," said Dr. Stephen O'Brien, leader of the AIDS genetics research team at the National Cancer Institute in Frederick. He is the senior author of a study appearing in today's edition of the journal Science.

O'Brien said that a better understanding of how the genes protect people could enable scientists to develop drugs, vaccines, gene therapies and even bone marrow transplants that give similar protection to others.

The discovery was made by drawing data from 1,955 people across the country who have exposed themselves repeatedly to the AIDS virus through high-risk sex, intravenous drug use and contaminated blood products.

The team found 17 who had inherited two copies of a mutated gene, one from each parent; all remained free of infection despite repeated encounters with the virus that causes acquired immune deficiency syndrome.

Others who inherited a single copy were not protected, but progressed more slowly to AIDS and lived longer once they acquired the virus.

At the very least, the finding may have solved part of a two-part mystery that has baffled scientists who have followed the epidemic: Why do some people remain virus-free despite their high-risk practices? And why do some infected people live for 10 or 15 years before progressing to AIDS, while others progress much sooner?

It also shows that some genetic alterations help people to stay healthy, in contrast to others that cause diseases such as cystic fibrosis or Huntington's chorea.

AIDS is caused by a virus, known as the human immunodeficiency virus (HIV), that invades important cells of the immune system -- crippling the body's ability to ward off killer infections. A gene, known as CKR5, produces a protein that sits on a cell's coat and serves as a doorway through which the AIDS virus enters.

But an altered form of the gene seems to impede the virus' entry, O'Brien said. One copy is enough to slow the pace of infection, while two block it entirely.

Based on data collected in the study, O'Brien said it appears that about 11 percent of the Caucasian population has one copy of the altered gene. About 1 percent has both copies.

A single mutation is present in about 1.7 percent of African Americans, while the double mutation is absent. Other scientists studying cultures in Africa have not found any evidence of the altered gene there, suggesting that black Americans who have one copy probably inherited it from white ancestors.

The discovery is an outgrowth of recent findings by Dr. Robert Gallo, director of the University of Maryland's Institute of Human Virology, and other scientists who identified a class of chemicals known as chemokines that are part of the body's natural defense against AIDS.

Gallo, interviewed yesterday, said the altered genes may block entry of the AIDS virus by boosting the body's production of chemokines.

"It may be encouraging the overproducing of chemokines, which interfere with the virus ever getting in the door," he said.

Gallo said it is likely that many people will want access to tests that can tell if they are genetically protected. "At the beginning, it would probably be cost prohibitive," he said.

The Frederick team drew data from several studies that have tracked the AIDS epidemic among high-risk populations. These included homosexual men, intravenous drug users and hemophiliacs.

Two studies were based at least in part at the Johns Hopkins Medical Institutions. The Alive study, led by Dr. David Vlahov, has followed the epidemic in a group of intravenous drug users in East Baltimore. That group, composed largely of African Americans, showed no evidence of natural protection.

Hopkins also has a major presence in the Multicenter AIDS Cohort, a study of homosexual men in four cities including Baltimore.

Pub Date: 9/27/96

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