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Vaccine Tests Stir Debate at World AIDS Conference

Times Medical Writer

New reports of laboratory progress toward developing an AIDS vaccine were presented Monday at an international conference on the deadly disease, but the news was tempered by a leading U.S. researcher’s warning that the efforts are probably doomed to failure.

“It is an unfortunate trick of nature, but the chances that a (conventional) vaccine is going to work are slight,” Dr. William Haseltine of Harvard Medical School told the gathering of more than 2,500 scientists at the Palais des Congres here.

Haseltine was commenting on the results of study done at Genentech Inc., the South San Francisco biotechnology firm, showing that an experimental vaccine could prevent the AIDS virus from infecting human cells in the laboratory, and on other reports, from scientists in Seattle and West Germany, on animal testing of a different type of vaccine.

The sharply differing assessments of the progress toward a vaccine underscore the complexity of the virus scientists are dealing with in their efforts to conquer the deadly acquired immune deficiency syndrome.

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Estimate of Epidemic

At the opening session of the three-day conference, Dr. Halphad Mahler, director general of the World Health Organization, estimated that about 100,000 cases of AIDS have developed worldwide, although fewer than 30,000 cases, in 92 countries, are officially acknowledged.

The official total includes about 22,000 cases reported in the United States since 1981, where an estimated 1 million to 1.5 million individuals are thought to be infected with the AIDS virus. Almost 12,000 Americans have died from the disease, for which there is yet no effective treatment.

In Africa, where the epidemic is thought to have started in the mid-1970s, perhaps several million people are infected, said Dr. Jonathan Mann, who oversees some of the World Health Organization’s anti-AIDS efforts there. “There are clear signs that AIDS is spreading to new areas of Africa and becoming more common in areas where it already exists,” said Mann, who spent several years studying the problem in Zaire.

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The advances toward developing a vaccine, described Monday, are in the very early stages. Before testing on humans would be possible, a potential AIDS vaccine would have to be proven safe and effective for treating a primate, a process that is likely to take at least until 1988.

DNA Technology Used

Dr. Laurence A. Lasky of Genentech explained how recombinant DNA techniques were used to make a test vaccine based on the so-called envelope protein, which forms the outer coating of the AIDS virus.

The protein was grown in large amounts in hamster cells in the laboratory, then purified and injected into rabbits and guinea pigs. In about 10 instances, antibodies to the virus produced in the test animals’ bodies have been shown to prevent the AIDS virus from infecting human T cells in the laboratory, Lasky said. This result could be viewed as significant, since the AIDS virus attacks and destroys T cells.

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In separate tests, researchers at Ontogen, a Seattle-based biotechnology firm, and others in West Germany used different genetic-engineering techniques to put genes for the AIDS envelope protein into a test virus, called the vaccinia virus. This modified virus was then injected into animals. Scientists confirmed that the animals’ bodies mounted immune responses to the AIDS envelope protein and the modified virus.

Haseltine told the conference, however, that some AIDS patients already produce antibodies similar to those under study, and that those antibodies have been proven ineffective for overcoming the disease.

Path of Virus Cited

The problem with these approaches, Haseltine said, is that the AIDS virus can spread from the inside of one cell directly to the inside of another, thus avoiding the bloodstream and escaping detection by the body’s immune system.

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Haseltine also said that the envelope proteins play an important role in the movement of the AIDS virus through the cells of the immune system. Envelope proteins can fuse cells to one another, and this facilitates the movement of the virus from cell to cell. “One infected cell can sweep through the immune system, killing hundreds of others,” he said.

Lasky said, however, that it would be “premature” to accept Haseltine’s viewpoint.


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