Drug Combination Prevents HIV Infection in Monkeys

(January 10, 2006) -- An injection of two drugs normally used to treat HIV patients completely protected monkeys from becoming infected with the AIDS virus, U.S. researchers reported on Monday.

While it is too early to tell whether people can pop a pill and escape infection, the study provides the strongest evidence yet that it might be possible, the researchers said.

Dr. Walid Heneine of the Centers for Disease and Prevention studied rhesus monkeys that were injected with a version of Truvada -- Gilead Sciences Inc.'s once-a-day pill that includes its drugs Viread, or tenofovir, and Emtriva, or emtracitibine.

The pill is often used in drug cocktails to treat HIV infection, although they cannot cure it.

The monkeys were then exposed to a combined human-monkey AIDS virus called SHIV, using a rectal method aimed at simulating male homosexual contact. That happened daily for 14 days and the monkeys also got daily injections.

"Treatment continued for four weeks after last challenge," Heneine told the Conference on Retroviruses and Opportunistic Infections, a meeting of AIDS researchers being held in Denver.

The six monkeys that received the drug combination were all completely protected from infection. By comparison, nine monkeys that took part in a previous experiment all eventually became infected with the SHIV virus.

"Study authors believe the findings may be the strongest animal data yet suggesting that potent antiretrovirals given before HIV exposure may prevent sexual HIV transmission," the CDC said in a statement.

The researchers cautioned the drug dose was slightly different from that seen in people taking Truvada and said studies under way will answer the question of whether the findings will translate to humans.

Either drug taken alone prevents HIV infection for a while, but imperfectly, Heneine said.

The CDC noted that Truvada was highly effective in suppressing the AIDS virus in people already infected. It is not a cure but is among the drugs that can help keep HIV patients healthy.

It also has fewer side effects than some of the older, hard-to-take combination regimens.

Dr. Myron Cohen of the University of North Carolina at Chapel Hill said the study suggested that people who know they are at high risk of infection might be able someday to protect themselves by taking a pill.

"Adolescent women in South Africa go from having a 10 percent risk of HIV infection to a 30 percent risk in a matter of two years," said Cohen, who was not involved in the study. "This is a big epidemic that is not going away."

In emerging nations, young women have the highest risk of becoming infected with HIV, often by husbands or boyfriends who refuse to use condoms.

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In richer countries, women are also at risk, as are men having sex with other men and injecting drug users. Cohen said these groups may also benefit from taking prophylactic doses of HIV drugs.

U.S. President George W. Bush's administration stresses abstinence as the best way to avoid AIDS, but Cohen and other experts said if the epidemic is to be stopped, people should make decisions based on science, rather than moral or emotional judgments.

"There are many other examples of people taking medications to protect themselves from disease," Cohen said.

Source: Routers

Last updated: 02/06

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