San Francisco Chronicle - Friday, June 9, 1989
David Perlman, Chronicle Science Editor

Salk made no claim that his research group is close to a true vaccine. But his unique approach is highly controversial among many other vaccine researchers here.

"I think we're on the right path," was all Salk would promise. "But we haven't gotten to the end of it," he told reporters at the fifth International AIDS Conference.

Salk's colleagues include Dr. Alexandra Levine of the University of Southern California, who has worked with volunteer gay men, and Dr. Clarence Gibbs of the National Institutes of Health in Bethesda, Md., who has been seeking to immunize chimpanzees.

All three scientists are basing their quest on the same vaccine concept that Salk used in his polio research days nearly 40 years ago.

They have used chemicals to strip away the protein coat of the AIDS virus, and radioactive cobalt to kill the remaining viral core. 19 MEN IN EXPERIMENT

Yesterday, Levine reported testing the killed virus material by injecting it into 19 men who were already infected with HIV, the AIDS virus, and who already showed symptoms of AIDS-related complex, the precursor to the full-blown disease. Their T-4 cells, crucial elements of the human immune system, were badly depleted.

Levine has now followed the men for more than a year, and she said her subjects have shown no evidence whatsoever that the killed virus material is toxic.

While the men showed no evidence that the injections killed the virus infection they already carried, 10 of the 19 volunteers showed significant increases in the levels of their T-4 cells, Levine said, and 16 have gained weight - some as much as 20 pounds.

Gibbs has been experimenting with four chimpanzees; two had already been infected with the human AIDS virus, one was uninfected at the start of the experiments, and one was not vaccinated at all.

After a single high-dose injection with the killed virus material and two subsequent booster shots, Gibbs reported, all evidence of virus infection had vanished from the two previously infected chimps. The uninfected animal showed clear evidence that he had developed antibodies to HIV after inoculation with the killed viral material, Gibbs reported. The healthy control chimp, who received none of the killed virus material but was later injected with live virus, showed only a primary immune response typical of anyone subjected to an infectious agent, according to Gibbs.

"All this," Salk said, "shows that we are moving in the direction toward controlling the progress of infection."

He said the human studies indicated that his killed virus material is safe, while the chimpanzee experiments indicate that even if a killed-virus vaccine cannot prevent infection, it should at least be able to prevent AIDS virus infections from progressing to disease. "NOT NECESSARILY DEATH SENTENCE'

"It all suggests that HIV infection is not necessarily a death sentence," Salk declared.

However, the work was not without its challengers at the AIDS conference.

Dr. Robert Gallo, one of the discoverers of the AIDS virus itself, suggested that although Salk's concept of a vaccine may eventually prove "of substantial importance" in slowing or even stopping the progress toward disease among people already infected with HIV, it would be dangerous to use such a vaccine in uninfected people.

"When you use a killed whole virus," Gallo told reporters, "it is impossible to guarantee that there isn't a danger that there is some live virus left in the material."

Most vaccine researchers, Gallo said, prefer to use segments of the outer envelope of the virus in their work. The viral envelope contains a variety of specific proteins that could induce the immune system to mobilize antibodies capable of destroying the invading virus, he noted.

Dr. Dani P. Bolognesi, director of Duke University's virus laboratory, and his colleagues are among those seeking vaccine material from among the varied viral coat proteins.

Bolognesi, one of the world's foremost experts on AIDS vaccine research, called Salk's work - particularly the chimpanzee experiments - "exciting and provocative."

However, he also voiced reservations that the animal work was not yet well-enough controlled to establish its true significance.

Both Bolognesi and Gallo have collaborated with scientists at the Repligen Corp., a small biotechnology firm in Cambridge, Mass., seeking to develop a vaccine based on some of the unique proteins that coat the surface of the HIV virus. HIV PROTEINS VARY

One problem is that these proteins vary from one strain of the virus to another, and spontaneous mutations alter their molecular nature frequently.

One such protein, termed RP135, exists on AIDS virus strains detected in a large proportion of infected Americans. Scott Putney, chief of molecular biology at Repligen, reported yesterday that the viral protein triggered the formation of antibodies against that protein in blood cells from 80 of 100 AIDS-infected volunteers.

The antibodies proved capable of neutralizing the surface protein on the virus, according to Putney and his colleagues. Their work suggests that a working vaccine might eventually be developed by creating a "cocktail" containing many sub-units of the proteins on the outer coat of the AIDS virus.

While all this work is moving swiftly, scientists at the Montreal conference predict with virtual unanimity that it will be years before a true vaccine will emerge from their research. Meanwhile, they continue to develop drugs that can successfully treat the many opportunistic infections that afflict people with AIDS.

Always watch for outdated information. This article first appeared in 1989. This material is designed to support, not replace, the relationship that exists between you and your doctor.

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