It worked in mice. It worked in monkeys. And now in humans, a therapeutic vaccine has stopped HIV in its tracks.

The vaccine is made from a patient's own dendritic cells (search) and HIV isolated from the patient's own blood. Dendritic cells are crucial to the immune response. They grab foreign bodies in the blood and present them to other immune cells to trigger powerful immune system responses to destroy the foreign invaders.

HIV infection normally turns these important immune system responses off. But animal studies show that when dendritic cells are "loaded" with whole, killed AIDS viruses, they can trigger effective immune responses that keep infected animals from dying of AIDS.

Wei Lu, Jean-Marie Andrieu, and colleagues at the University of Paris in France and Pernambuco Federal University in Recife, Brazil, tested the vaccine on 18 Brazilian patients. All had HIV infection for at least a year. Their T-cell counts — a crucial measure of AIDS progression — were dropping, meaning their disease was worsening. None was taking anti-HIV medications.

After getting three under-the-skin injections of the tailor-made vaccine, the amount of HIV in the patients' blood (called the viral load) dropped by 80 percent. After a year, eight of the 18 patients still had a 90 percent drop in HIV levels. All patients' T-cell counts stopped dropping.

The findings appear in the December issue of Nature Medicine.

"The results suggest that [these] vaccines could be a promising strategy for treating people with chronic HIV infection," Andrieu and colleagues write. "The significant decrease of viral load as well as maintenance of ... [T-]cell counts observed at one year after immunization are particularly promising."

The researchers warn that their study is only proof of principle. It's still not clear which patients do best with the vaccine, although there's evidence that vaccination should be given as soon after HIV infection as possible. Only clinical trials comparing people who get the vaccine to those who don't can show whether this vaccine really is an effective AIDS therapy.

Similar approaches are being explored for the treatment of cancer and long-term viral infections such as hepatitis C.

By Daniel J. DeNoon, reviewed by Charlotte E. Grayson, MD

SOURCE: Lu, W. Nature Medicine, December 2004, advance online publication.