December 10, 2008

Possible AIDS Treatment Shows Promise in Monkeys

WEDNESDAY, Dec. 10 (HealthDay News) -- Researchers report that a treatment under development appears to stop the equivalent of the AIDS virus in monkeys.

Nine rhesus macaque monkeys infected with a virus known as SIV underwent treatment and remain alive eight months later. The treatment appears to work by preventing virus cells from fooling the immune system.

There's no guarantee that the treatment will work in people. But if it's effective in humans, the treatment could allow patients to avoid taking AIDS drugs for the rest of their lives, said study co-author Rama Rao Amara, an assistant professor at Emory University's Yerkes National Primate Research Center.

"If you wake up and realize you don't have to take a pill, it's a big step forward," he said. In addition, he said, current AIDS drugs are expensive and have serious side effects.

Existing AIDS drugs do have benefits: They're often effective and have allowed patients to live normal lives. However, they can't always keep up with the AIDS virus, which evolves quickly and can become immune to current treatments.

"The virus changes and then these drugs don't work after some time," Amara said.

In the new study, Amara and colleagues injected nine monkeys with an antibody that blocks a kind of "don't kill me" signal that cells infected with simian immunodeficiency virus (SIV) send to immune cells.

When the SIV-infected cells emit the signal, "the killer cell thinks, 'You are not my enemy. You're my friend,'" Amara said. But when the signal is blocked, the killer immune cells can do their job and wipe out the virus.

The researchers gave four injections of the antibody to the monkeys over 10 days and then watched to see what happened.

The study appears in the Dec. 10 online edition of Nature

The monkeys, infected with SIV for as long as 21 months, were able to beat back the virus. Levels of virus in the blood dropped and the animals remained alive.

By contrast, four out of five monkeys who received a "control" antibody died within four months.

"What is amazing to me how rapidly you can actually change these killer cells," Amara said. "Now they are good cells."

The work of the monkeys is done and they will be euthanized, Amara said. It is too expensive -- $7 a day each -- to pay for their care with available funding, he said.

In humans, the treatment could cost a couple thousand dollars per dose, Amara said, although patients might then avoid taking drugs for life.

Dr. Mark Connors, a specialist in AIDS research, said the research is "clearly valid and very interesting. I'm sure it's going to generate debate over the next year or so as to what it means."

Even skeptics may be convinced by evidence that the treatment directly affects survival and the level of the virus in the body, said Connors, chief of the HIV-Specific Immunity Section at the U.S. National Institute of Allergy & Infectious Diseases.

As for the future, Connors said he's "guardedly optimistic" that the treatment could be used in humans, perhaps in conjunction with other medications.

More information

To learn more about AIDS, go to AIDS.gov.

SOURCES: Rama Rao Amara, Ph.D., assistant professor, Yerkes National Primate Research Center, Emory University, Atlanta; Mark Connors, M.D., chief, HIV-Specific Immunity Section, U.S. National Institute of Allergy & Infectious Diseases, Bethesda, Md.; Dec. 10, 2008, Nature, online
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