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    AIDS/Smallpox Vaccine OK in Early Test

    AIDS Vaccine That Protects Monkeys Looks Good in First Human Test

    AIDS Vaccine in 4 Years?

    There are two basic kinds of immunity. Cell-based immune responses depend on killer blood cells that seek out and destroy infected cells. Antibody-based immune responses depend on antibodies that stick to germs or infected cells, inactivating them and marking them for destruction.

    The GeoVax vaccine is designed to stimulate both kinds of immunity. The immune responses seen with one-tenth doses of the vaccine were cell-based responses. However, Robinson says she also expects to see anti-HIV antibodies in volunteers to get the full dose of the vaccine.

    That study already is under way. Thirty volunteers are getting the full dose of the vaccine while six get mock injections. Results of that study should be known later this year.

    Meanwhile, Robinson and colleagues are gearing up for a phase II study of the vaccine, which will involve hundreds of HIV-negative volunteers. Because of the promising phase I results, that trial has been moved up by a year and a half, Robinson says.

    "The fact we are getting such good immune responses in humans is very encouraging," Robinson says. "We are moving forward, and if everything really goes absolutely smoothly, we could have a vaccine in four years."

    That could happen, although in real-life vaccine and drug development, things rarely go so perfectly.

    Two similar vaccines -- using adenovirus instead of smallpox virus -- are further along than the GeoVax vaccine.

    Drug giant Merck has a genetically engineered adenovirus vaccine that carries elements of the HIV gag, pol, and nef genes. That vaccine is being tested in some 3,000 people at high risk of infection in the U.S. and Africa.

    The National Institutes of Health also has a genetically engineered adenovirus vaccine, carrying the HIV env, gag, and pol genes, which is used to boost DNA vaccination with the same genes. That vaccine is in early phase II trials involving hundreds of volunteers.

    "With HIV vaccines, we are still at an early stage where we need to understand whether anything can influence HIV infection," Keefer says. "If we can get protection from anything, we will build on that. None of us in the vaccine world expect a home run right away."

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