First AIDS Vaccine Trial Launched

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Science  12 Jun 1998:
Vol. 280, Issue 5370, pp. 1697
DOI: 10.1126/science.280.5370.1697a

The first full-scale clinical trial of an AIDS vaccine is set to begin this month. VaxGen Inc. of South San Francisco announced on 3 June that the Food and Drug Administration has given it the green light to begin trials of its product, AIDSVAX, in thousands of volunteers in the United States and Thailand.

AIDSVAX is based on an HIV envelope protein, gp120, which stimulates antibody production. It has performed impressively in animals, but results in human volunteers have been disappointing.

Researchers are still divided over whether to move ahead with something that may be partially successful or wait for a more promising vaccine (Science, 30 January, p. 650). One leading voice of caution is that of Caltech President David Baltimore, who heads a committee overseeing the government's AIDS vaccine effort. Baltimore says not only he but most of the research community regards it as “extremely unlikely” that the vaccine can confer total immunity, and he questions whether the samples are even large enough to determine if vaccination can “dampen the effect” of infection.

The U.S. subject population is 5000 gay men and a few un-infected heterosexuals whose partners are HIV-positive. Two-thirds will be vaccinated over a 3-year period and the rest given a placebo. In Thailand, where the rate of new infections is higher, half of a group of 2500 uninfected intravenous drug users will be vaccinated. The vaccine will be assessed by two measures, says VaxGen President Donald Francis: infection by HIV and viral load in those infected.

Some scientists doubt that any vaccine can work if it only boosts antibodies and does not also affect another part of the immune system, killer T cells. Francis is undeterred, saying “we base a lot of our confidence on the fact we can protect the chimpanzee from a very large intravenous [viral] challenge.”

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