SALK VACCINE FOR AIDS

By Christine Gorman

Salk and vaccine. the words somehow belong together-like Fleming and penicillin or Einstein and relativity. So when Dr. Jonas Salk, the developer of the first effective vaccine against polio, announced eight years ago that he was coming out of retirement to tackle AIDS, many people cheered-especially the growing numbers of patients infected with hiv. Who better to lead the charge against the current plague than the conqueror of an infamous childhood scourge? Within the scientific community, though, there was more doubt than expectation. AIDS was a tougher target than polio, and few experts believed that Salk's approach to making a vaccine would work.

Undeterred by the skeptics, the medical pioneer forged ahead and joined forces with a private company to develop his treatment. Now Salk, 80, may get a chance to prove he has one more medical miracle up the sleeve of his lab coat. Last week an expert advisory panel to the Food and Drug Administration recommended that the agency allow Salk to test his AIDS vaccine on 5,000 volunteers. If the FDA agrees, Salk's preparation would be the first AIDS vaccine to undergo a large-scale trial in the U.S.

Yet the endorsement was hardly ringing, because the early evidence of the vaccine's worth, from tests involving small numbers of patients, was far from compelling. The panel's vote split 6 to 3 in favor of further testing, with one member undecided. "I am not all that excited about the data I've seen," admits committee chairman Dr. Stanley Lemon of the University of North Carolina. "But I would be thrilled to be proven wrong."

Unlike traditional vaccines, which are designed to prevent infection, Salk's new treatment is given to people who are already infected with hiv. Once every three months, they receive a shot of vaccine, manufactured by the Immune Response Co. of Carlsbad, California, that is supposed to boost their flagging immune system and decrease the amount of virus circulating in the blood. But new research, reported last month by teams led by Dr. David Ho of the Aaron Diamond AIDS Research Center in New York City and Dr. George Shaw of the University of Alabama at Birmingham, suggests that this so-called therapeutic-vaccine approach may be the wrong way to go. They found that even during the early stages of infection, the immune system is already working hard, and a vaccination probably would not provide a boost. In light of his own research and an early peek at Salk's data, Ho believes "there is absolutely no evidence that the vaccine did any good."

Then why did the FDA panel vote for wider testing? Clearly, Salk himself was a big selling point. "He has a reputation among some scientists as a god," says one top AIDS researcher. "He's a powerful advocate, and they find it very hard to turn him down." The committee may also have had a hard time saying no to the AIDS patients who participated in the early pilot programs. They fear that if the FDA does not expand the trial, they will no longer receive the shots. And many are convinced that the treatments are helping. Mike Slattery of Los Angeles, who began receiving Salk's vaccine in 1988, cites lab tests showing that his immune system is deteriorating more slowly than might otherwise be expected. "I'm going to live 10 years longer because of this," he says. "This may provide a bridge so that I will be alive when effective treatments arrive."

That kind of endorsement-and sense of urgency-is what motivates Salk. "We want desperately now to move forward," he told the panel last week. "You can fail only if you stop too soon." Despite criticism of the treatment, Salk and his business partners remain confident. "When we started this in 1987, no one believed in therapeutic vaccines," says Dennis Carlo, president of Immune Response. "Our product has stood the test of time.''

In a way, the FDA panel has merely passed the buck on deciding whether Salk can succeed in stopping two epidemics in a single lifetime. The political pressure to try his approach is just too intense. "The only way the concept is going to be laid to rest as a concept that does not work is really to try it in a large population," FDA adviser Lemon says. Since the vaccine apparently does no harm, since no other treatment has proved to be effective and since most patients are facing a death sentence, the panel elected to give Salk every opportunity to make his case.

But such a policy is not without pitfalls. If patients participate in the trial of an ineffective treatment, they may not get a chance to try better therapies that come along later. That is the reason the FDA traditionally insists on significant evidence of effectiveness before approving large trials. "By lowering the standards we have increased the level of confusion about how to treat people with AIDS," says Dr. Deborah Cotton of Massachusetts General Hospital. And until Salk and other researchers can end that confusion, AIDS will continue to take a ghastly toll.

--Reported by Alice Park/ New York and Dick Thompson/Washington

With reporting by ALICE PARK/ NEW YORK AND DICK THOMPSON/WASHINGTON