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Giving potential AIDS vaccines a 'boost.'

Giving potential AIDS vaccines a "boost'

To ensure adequate immunity against disease, vaccinations frequently are followed by booster shots to stimulate an individual's "immunologic memory.' Two studies--one in the first humans known to be injected with an experimental AIDS vaccine, the other in chimpanzees--are suggesting that this so-called anamnestic response could be a viable part of AIDS vaccination.

In March, Daniel Zagury of the Pierre and Marie Curie Institute in Paris and his co-workers announced that they had injected a small group of volunteers in Zaire (including Zagury) with a potential AIDS vaccine (SN: 3/28/87, p.198). The new vaccine--made by inserting a gene for the AIDS virus (HIV) envelope into vaccinia virus used to make smallpox vaccine --caused antibody production and activated immune cells.

After the initial immunizations, 12 of the volunteers each received one of four possible "booster' preparations: the recombinant vaccinia vaccine itself, a portion of the HIV envelope segment used to make the vaccine, whole cells taken from an immunized subject and infected in vitro with the recombinant vaccinia before being injected back into the same person (autologous cells) or just the membranes from the vaccinia-infected autologous cells. The researchers had "fixed' whole cells with parafor-maldehyde to maintain their surface structures, recognized by an ammune system already primed by vaccination.

On Dec. 11, Zagury discussed the results at the Fourth International Symposium on Cancer Research, held at the National Institutes of Health in Bethesda, Md., and organized by the French Association for Cancer Research. Ten days after booster shots were given, the most "marked responses' of both antibody production and cellular immunity were seen with blood samples from Zagury himself, who was the only one to receive the whole autologous cells. Subsequent tests showed that the boosting treatment caused no side effects, and Zagury concludes that this treatment should be considered a possible "prototype of candidate vaccines.'

A National Cancer Institute study in chimpanzees could give the booster-shot issue added insight: Unlike the human volunteers, laboratory animals can be "challenged' with actual HIV infection. Peter J. Fischinger, now at Health and Human Services headquarters in Washington, D.C., said at the symposium that yet-unpublished data indicate that--after several boosting immunizations with the vaccine followed by challenges with HIV --chimps showed an immune response not only against the HIV strain used to make the vaccine, but also against additional strains. This is encouraging for scientists who worry that HIV's high rate of mutation would make it difficult for a single vaccine to protect against multiple strains.

Zagury's group plans to add substances called adjuvants to the vaccine to heighten immune responses, in order to "mimic' the boosting protocol in a way more practical for larger groups, says Zagury.

In another study looking for cell cultures that might produce monoclonal antibodies against HIV, the group has isolated 42 antibody-producing clones out of 400 tested thus far. They hope to use these genetically engineered antibodies to protect developing fetuses in pregnant, HIV-infected women in Africa, says Zagury.
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Author:Edwards, Diane D.
Publication:Science News
Date:Dec 19, 1987
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