AIDS researchers report few gains in fighting disease as meeting closes

June 12, 1993|By New York Times News Service

BERLIN -- The ninth international meeting on AIDS ended yesterday after 5,500 presentations that showed little more than incremental gains in scientific knowledge about the disease.

"Our progress seems desperately slow," Dr. Michael H. Merson, the director of the World Health Organization's AIDS program, said at the close of the weeklong meeting. His remarks to the more than 14,000 participants also reflected gloom about the spread of the human immunodeficiency virus (HIV), which causes AIDS, in many areas of the world.

"With regard to science, it's best to be frank," Dr. Merson said. "We cannot report the big breakthroughs on preventive vaccines for which the world is waiting."

He added that "there have been disappointments" in drug treatment aimed at the virus. "We must accept that our scientific advances today are coming in small steps, not in leaps and bounds," he said.

Nevertheless, Dr. Lars O. Kallings, a Swedish epidemiologist, said the meeting offered abundant new information about vaccines, the dynamics of the spread of the various genetic subtypes of HIV, and the way the virus damages the immune system.

Experimental vaccines made by genetic engineering techniques areshowing evidence of high levels of immune responses that are lasting longer in human volunteers than researchers had expected, said Dr. Dani P. Bolognesi of Duke University.

In a meeting at WHO's headquarters in Geneva last week, experts urged intensive exploration of vaccines made from weakened live virus instead of those made by genetic engineering techniques.

Most scientists have feared developing such attenuated vaccines for AIDS because the virus in the vaccine, though weakened, could still mutate and cause disease.

But faced with a relentless epidemic, attitudes began to change after a report from scientists at the New England Regional Primate Center in Southborough, Mass., who made an attenuated vaccine by removing a gene from the simian AIDS virus, which is related to the human AIDS virus and inflicts a disease that closely parallels AIDS in humans. The resulting vaccine offered the strongest protection to date.

Vaccine researchers are fighting an ever-changing AIDS virus.

Scientists can identify five, perhaps six, major genetic subtypes of HIV-1, the main AIDS virus. Different subtypes predominate in different parts of the world.

But in Thailand, one subtype of HIV has overtaken another over the last two years. A similar phenomenon is occurring in South America, where the formerly dominant strain is about to be replaced by others.

"It is only a matter of time before new subtypes take hold" in many parts of the world, and the changes have clear implications for an AIDS vaccine, Dr. Kallings said.

Researchers had believed that they could develop a vaccine against the dominant strain in a geographic region. But with the virus migration, it now appears that a world vaccine will be needed, Dr. Kallings said. He also suggested that scientists may need to monitor HIV as they do the influenza virus so that the vaccine can be adjusted each year to target the latest mutations.

The news about anti-HIV drugs at the meeting was disappointing.

Last month, a European study that its authors described as the largest, longest and statistically most powerful to evaluate the AIDS drug AZT, found that its use in the early treatment of HIV did not delay the onset of AIDS or prolong life.

Some American scientists were critical of the design of the European study. But after Dr. Maxine Seligmann of Paris reported additional data from the study, even the critics said it was sound.

But doctors still do not know what is the best time to start AZT therapy. A clearer picture may emerge from a meeting on the early treatment of HIV infection later this month at the National Institutes of Health in Bethesda, Md.

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