Skepticism Greets AIDS Trial Offer
Researchers seeking to develop an AIDS vaccine addressed with skepticism Monday, even an undercurrent of scorn, the announcement by a physicians’ group that 50 volunteers are willing to subject themselves to an injection of a live, weakened strain of the virus that causes the disease.
The goal of the International Assn. of Physicians in AIDS Care would be to speed up the often-ponderous scientific process that has rested historically at the root of developing lifesaving vaccines.
But, using cautious language even as they said privately that the proposal smacks of grandstanding, scientists said that such seemingly altruistic human testing, born of frustration, would short-circuit proven safety procedures while offering little of scientific value.
This is because the testing group would be too small to determine whether the vaccine they would receive was ultimately safe. Also, researchers must determine whether such a vaccine, born of live virus, can be reproduced to precise specifications dose after dose.
“Otherwise, there is no value to the experiment,” said a former government researcher now involved in a major drug company’s AIDS research.
In any case, said Peggy Johnston, the scientific director of the International AIDS Vaccine Initiative, a nonprofit group established to ensure the development of a safe AIDS vaccine, the proposal raised by the physicians’ group in Chicago is for now a case of much ado about nothing: There is no vaccine to test.
It may be an intriguing proposal and one that may stimulate debate, she said, but at its heart the question of a vaccine remains conceptual.
“There isn’t a product in a bottle a physician can inject into the arm,” Johnston said.
The volunteers’ proposal, the subject of news stories over the weekend, prompted a surge of telephone calls to the organization’s offices in Chicago on Monday. It said that it has a list of 50 people willing to participate in a trial of a vaccine and dozens of others seeking to add their names to the list.
The group said it would proceed with a test--of specifically what vaccine was not clear--with or without government approval.
Tests of a vaccine would involve injecting a live, but weakened, version of the HIV virus to stimulate the body’s natural defenses. The vaccines that prevent measles, mumps, rubella, polio and yellow fever all have been derived from such live viruses.
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But, without further studies, scientists worry that injection of a live, weakened HIV virus could lead to infection rather than a protective response.
The group claims that there is a vaccine to be tested, the human counterpart of a weakened vaccine tested in monkeys. Dr. Donald Desrosiers of Harvard University first produced a weakened strain of the monkey analog of HIV--called simian immunodeficiency virus, or SIV. Two monkeys immunized with the weakened virus in 1989 are alive and well, despite being exposed to massive doses of SIV.
Desrosiers has subsequently developed a weakened version of the human AIDS virus similar in design to the monkey vaccine. Desrosiers has called for human tests of that vaccine, but other scientists have raised ethical concerns.
Critics fear that the mutated virus may be able to regain its full strength in humans and cause AIDS. HIV, furthermore, is a retrovirus, a class of viruses that is known to cause cancer. Opponents argue that the risks of long-term exposure to even a weakened retrovirus are too high to justify the use of such a vaccine.
The proposed Harvard vaccine is markedly different from other AIDS vaccines now being studied. None of those has the live virus. They all incorporate one or more viral proteins, particularly those found on the surface of HIV, in hopes of stimulating immunity without the risk of infection.
But none of those vaccines provokes a strong immune response. In other diseases, moreover, the best protection has been provided by vaccines containing weakened live viruses, such as those for measles, tuberculosis and polio.
For the moment, at least, most researchers believe that tests of a live-virus HIV vaccine are simply too risky.
The Food and Drug Administration, which ultimately would be responsible for licensing any vaccine used in the United States, was reluctant to comment.
FDA spokeswoman Ivy Kupec said: “You can say it’s risky with a live virus, but if the trial design was a good one, I don’t think the FDA would want to stop that from happening. They haven’t been told they can’t by us.”
As explained by researchers, development of vaccines is a lengthy process involving science, art and luck. No viral vaccine has been developed in fewer than two years, Haynes Sheppard, a researcher with the California Department of Health Services, has said.
Although dozens of potential products are under scrutiny, none has proved compelling enough for a large-scale trial, in which tens of thousands of high-risk individuals would be studied to determine whether a vaccine actually would protect them against infection.
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The focus of the Chicago group’s offer is the vaccine that appears to protect monkeys from SIV, the primate equivalent of HIV. But researchers say the laboratory virus strain to which the monkeys were exposed is not necessarily like the human strain.
Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, said the proposal is premature at best.
“It doesn’t do the field any good, given the state of the art, to go ahead and inject 40 or 50 people,” he said. “When you’re talking about trials of vaccines in people, well, it behooves you to behave very favorably in favor of safety. Animal models and test-tube testing has to be undertaken before you put it in a human.
“I commend these people for being altruistic in volunteering for something like this, but as a scientist, I think it’s premature. What would this tell us about safety? It tells us nothing,” Fauci said.
Times medical writer Thomas M. Maugh II contributed to this story from Los Angeles.
