OPTIMISM TO MARK AIDS CONFERENCE.

Byline: Daniel Q. Haney Associated Press 

The 11th International Conference on AIDS will open today with something entirely new in the brief history of the epidemic: a barely containable sense of optimism.

The euphoric shift in mood is as dramatic - and as surprising - as the scientific breakthroughs that triggered it. For the first time, the idea is beginning to sink in that HIV might not be a death sentence after all.

``People are much more enthusiastic about what we have to offer,'' said Dr. John G. Bartlett of Johns Hopkins University. ``We have had an avalanche of new drugs. The perception is that we can much more effectively deal with the virus.''

There might even be - and this word is at last being said out loud - the possibility of a cure.

Moreover, experts see the first glimmer that AIDS can be turned back in the developing world, too, even in places where the new AIDS drugs are too expensive to make much difference. Condom campaigns at last appear to be slowing the spread of the virus in Africa and Asia.

Such changes were virtually unimaginable two years ago when the conference was last held in Yokohama, Japan. The outlook then could hardly have been more bleak. The available AIDS medicines worked poorly, if at all, and nothing much better seemed likely.

But in the past six months, the momentum has turned; the news has suddenly become astonishingly good. As 15,000 people gather in Vancouver, British Columbia, from 125 countries to talk about AIDS, almost anything seems possible.

The key discovery is the power of combining AIDS medicines. Alone, none of these drugs does much. Together, they seem to stop the virus cold.

``We now know that the drugs we have can work far better than we had hoped. For many patients, this will be a much more treatable illness,'' said Dr. Cal Cohen, who treats AIDS at the Harvard Community Health Plan in Boston.

How treatable? More specific evidence is expected at this week's meeting. But many of those on the front lines of AIDS seem to agree with Dr. William Paul, head of the U.S. Office of AIDS Research.

``I can imagine that the drug therapies will put us in the position where AIDS becomes a chronic, manageable disease,'' he said.

In these doctors' view, AIDS may well become something like diabetes or high blood pressure, illnesses that can be kept in check with careful, lifelong treatment.

In all, nine AIDS drugs are on the U.S. market, five of them introduced in the past half-year. The most important are three in a new class called protease inhibitors, which block one step in HIV's reproductive cycle. When combined with two older AIDS drugs, the virus appears to stop reproducing.

People have been taking various three-drug combinations for about 18 months, and in many - but not all - every trace of HIV disappears from the bloodstream.

``We are talking about a brand-new paradigm, which is to completely suppress virus replication,'' said Dr. Douglas D. Richman of the University of California, San Diego.

If the virus cannot make new copies of itself, it cannot destroy the immune system. So in theory, patients should be able to live reasonably healthy lives, if AIDS has not already done irreparable damage.

Even though undetectable, however, the virus is not gone. It lingers quietly inside cells. But in time, many of these infected cells will die off.

``If the patient suppresses it long enough, will the last embers of the virus become extinct so the virus is cured?'' Richman asks. ``We don't know if it can be or not.''

A cure. So seemingly unachievable, the word became all but taboo, and it still gives some researchers the shivers.

``I refuse to say that word at this point,'' said Dr. Richard D'Aquila of Massachusetts General Hospital. ``But people are beginning to think about how much you can suppress the virus and how long you can keep it suppressed to begin to think about experiments to do that.''

Some believe the best chance of a cure is to start treatment as soon as people know they are infected, ideally within weeks of catching the virus. This may head off HIV before it becomes established in the brain and other hard-to-treat parts of the body.

Some worry, though, that exhilaration about recent advances will raise hopes too high, especially considering HIV's uncanny ability to sidestep scientists' brightest ideas.

``One possibility is that the virus, which we know is very cunning, may figure out a way to build resistance in another year or 18 months,'' said Larry Kessler, head of Boston's AIDS Action Committee.

He, like many in the fight against AIDS, is not ready to declare victory. ``We see a glow at the end of the tunnel,'' he said. ``But we don't see the light.''

Nevertheless, many at the meeting are buoyed by patients like Brian Rosenberg, 31, of Boston, who learned a few days ago that HIV had disappeared from his bloodstream after probably eight years of infection.

``It was great news,'' he said. ``It has put time into my future, so I will be around and healthy enough to take advantage of whatever comes next.''