Important note: Information in this article was accurate in 1998. The state of the art may have changed since the publication date.

Reuters NewMedia, Inc.; Thursday July 2 9:10 AM EDT
Jonathan Birt

Gallo said work should concentrate on methods of blocking the virus from entering healthy cells, moving on from current therapies which stop it reproducing.

He also gave an upbeat assessment of a simple vaccine already tried in humans that could stimulate the body's own defenses against invasion by HIV, offering the first real hope of treatment for millions of HIV-infected people in the third world.

But he told a meeting at the 12th World AIDS Conference that it was too soon to pour all available resources into the quest for a preventative vaccine, which had uncertain prospects and would do nothing to help the tens of millions of people in poorer countries already infected with the virus.

Gallo, who is director of the Institute of Virology at the University of Maryland, Baltimore, said existing drug therapies had been very successful, but the threat of toxicity building up from long-term use and a build up of resistance by the virus had to be faced.

"For some people it is going very well, but the problem of compliance is there. We have to face up to the toxicity and solve the third world problem," he said. "Despite great advances in therapy against HIV and the likelihood of additional anti-HIV chemical inhibitors being developed in the coming years, the problem of treatment for HIV-infected people is not solved."

In 1995 Gallo and other colleagues demonstrated that chemokines -- proteins which play a role in inflammation -- can naturally block the entry of the HIV virus into healthy cells.

Chemokines have been likened to bouncers at a night club -- the more you have, the better able they are to keep out undesirable elements. Gallo pointed to a group of hemophiliacs repeatedly inoculated with HIV-infected blood up to 1985 who had not become HIV-positive.

He said they were found to have more than twice the level of chemokines in their blood than those who became infected.

Treatments and preventative drugs based on chemokines could be in place in three or four years time, he believes.

Creation of drugs which stop so-called fusion of the virus with healthy cells -- already the subject of much discussion at the conference -- is another promising area, Gallo said.

The third main target would be a vaccine to stimulate the immune system by lowering levels of interferon, which can help destroy the body's defenses, and another protein called tat. The vaccine has been tested on a small number of people in Europe for three years with promising results, and larger scale trials are due to start in Baltimore later this year.

Administered perhaps three times a year, it could be the first cost-effective way of treating most of the 40 million people likely to be infected by AIDS by the turn of the century.

Although optimistic about vaccines that treat AIDS, Gallo was cautious about prospects for one that will prevent the condition altogether. "On a preventative vaccine I can't promise anything," he said. "In 1984 I was asked by the (U.S.) secretary of health when we would have a (preventative) vaccine, and I said about three years."

Gallo's pessimism about a preventative vaccine was underscored by Ruth Ruprecht of Harvard University.

She told the conference a five-year experiment using a supposedly disabled, or attenuated, version of the HIV virus to stimulate an immune response in monkeys had failed, with most of the monkeys either dead or sick from AIDS.

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