Miami Herald - Thursday September 3, 1987
Ena Naunton, Herald Staff Writer

Other scientists reach out to catch onto these ideas, putting them to the test of whether they truly advance medical research. Often the discoveries are rejected and never seen again.

Recently, an AIDS research report flew out of London, eddied around a bit and dropped over to Holland and France. Now, although a bit bent, that "straw" is still in circulation.

It comes from a British study suggesting that a simple blood test, currently used to settle questions of paternity, might explain why some people exposed to the AIDS virus are infected while others are not. A group of doctors at St. Mary's Hospital Medical School in London examined about 200 people who had AIDS or the virus that causes it or were healthy but known to be at special risk through sexual contact with persons with AIDS.

Reporting in the May 2 issue of the distinguished British medical journal The Lancet, the doctors said they discovered a common genetic pattern among homosexual men with AIDS and another among those who had escaped infection. Once a person was infected, they said, genes appeared to influence the severity of subsequent illness.

The British researchers said that of those exposed, even repeatedly, to the Human Immunodeficiency Virus (HIV) that spreads AIDS, only 50 to 60 percent are infected. Nobody knows why the other 40 to 50 percent are apparently immune.

Scientists do know that, over thousands of years, genetic mutations have produced people who are naturally protected from certain infectious diseases, notably malaria and tuberculosis. The same holds true for genetic susceptibility to some noninfectious diseases. For instance, sickle cell anemia, a painful and dangerous illness that strikes one in 500 American blacks, has its origins in the genetic protection from malaria their ancestors developed long ago in Africa.

Simplistically, genetic mutation apparently affects how receptive blood cells are to being penetrated by viruses. In one person, the virus latches on and does its deadly work; in another, because of the presence of a different genetic component on the surface of the blood cells, the virus just floats by, unable to set up housekeeping.

The possibility that some people may be protected from either catching AIDS or dying from it might depend upon how they inherited a protein called Gc (group-specific component), which is present in all of us. Gc helps our bodies process vitamin D, which we get from sunlight on our skins. Some people have different variations of Gc from others, depending upon the origins, mating habits and global wanderings of their ancestors -- and perhaps upon how close to the sun those ancestors lived.

One variant of Gc, known as Gc1F, is found most commonly among natives of a large area of Africa.

"Perhaps this high African frequency of Gc1F is among the factors that contributed to the spread of AIDS there," wrote Dr. Jared Diamond, of the UCLA medical school, reviewing the British study in the July 16 issue of Nature, the international science journal.

Furthermore, when the British doctors looked at white homosexuals in London, they discovered "patients with full-blown AIDS showed the highest frequency of Gc1F." They completely lacked another variant, called Gc2-2, which was found most often among people consistently free of the AIDS virus despite their sexual intercourse with persons who had AIDS.

Dr. Karl Muench, chief of the division of genetic medicine at the University of Miami School of Medicine, called the British study "very exciting." Using textbook tables of the variations of Gc protein found in the population at large, he was astounded to see a parallel to the published incidence of AIDS in various ethnic and racial groups.

While the merits of the study are being debated, anyone wanting the test could have trouble finding a laboratory to do it. Muench customarily orders paternity tests from the Diaclin laboratory in Nashville, Tenn. Jerry Morrisey, a lab director there, expressed doubts about the validity of the British data.

"I still think some improvement needs to be done in terms of data base as to whether there's any significant effect (to the test)," he said. Such a test might cost from $10 to $30, he said, but his own lab is not doing it. Most labs would do the Gc test only at the request of a doctor.

"It would obviously be for a physician to interpret results," Morrisey said.

"It's really quite a simple test to do," said Dr. Geoffrey O'Neill, director of the tissue typing lab at Red Cross Blood Services in Miami. But anyone worried about AIDS risks can't expect to get the test there yet, either. O'Neill said he is considering the feasibility of adding the Gc test to the AIDS-virus test already used on all donated blood to protect the blood supply.

Before anyone gets excited and thinks that the British doctors have discovered the answer to the AIDS epidemic, it's well to remember that hundreds, if not thousands, of scientists are trying to get a handle on how to stop the spread of the disease.

There are weaknesses in the British material -- not the least being the small size of the group studied. Letters published in early August editions of The Lancet said scientists in Holland and France had not been able to duplicate the St. Mary's Hospital results. Duplication of research results is the acid test for any laboratory discovery.

However, the debate is still alive. Even after reading the questions raised by the French and Dutch researchers, O'Neill said "It seems unlikely that there is nothing to (the British) data. This will require many other studies."

Perhaps, as the Nature reviewer suggests, this new genetic quirk is something that will interest only future generations who might develop immunity to AIDS as the survivors of malaria epidemics did long ago. For the present generation, the British results "could turn out not to be confirmed or not terribly relevant," Muench said. Only time and very careful science will tell.
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