Next on AIDS' Frontier

Although the first AIDS vaccine to undergo advanced human trials, Aidsvax, was an acknowledged failure by its makers, researchers and advocates are not giving up. Vaccines are considered the ultimate goal in preventing new HIV/AIDS infections.

Currently, about 19 vaccines are in human trials, but mostly in early studies designed to show that they are safe and can mobilize the body's disease-fighting systems. "We have a field of them that are doing pretty well in animal studies. But the nature of vaccine research is that if you had the perfect vaccine tomorrow, it would take you almost 10 years to prove it and get it to the regulatory stage," said Martin Delaney, founder of Project Inform, an AIDS group in San Francisco.

Vaccines that use a two-step process by firing up antibody and cellular immunity are among those in early human trials. Such a two-part vaccine works by producing antibodies that prevent HIV from entering disease-fighting T-cells and then dispatching immune cells to destroy HIV-infected cells.

Several research groups are also trying to engineer a better antibody-inducing vaccine, either used alone or in combination with a cellular immunity vaccine, according to Dr. John P. Moore, who runs an AIDS research laboratory at Weill Cornell Medical College in New York City. In addition, two vaccines that generate cellular immunity are also garnering attention. One uses adenovirus, which seems to stimulate a more prolonged immune response than other viruses, to ferry genes into target cells. The other contains an initial shot of HIV genes and a booster shot of modified vaccinia Ankara, which resembles the virus in smallpox vaccines, containing other HIV genes.

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