Herpes Drug May Help Control AIDS Virus

A cheap, generic treatment used against herpes can also lower HIV viral load, researchers reported Wednesday. However, acyclovir works against HIV only in tissues that are also infected with herpes. The findings could help explain why some studies have shown that patients taking acyclovir have a lower HIV viral load, while in several high-profile experiments the drug failed to prevent HIV infection.

The herpes virus changes acyclovir into a form that works against HIV, said study co-leader Dr. Leonid Margolis of the National Institute of Child Health and Human Development. The drug does not become active until it encounters a herpes virus, usually herpes simplex virus type 2, or genital herpes. The virus completes a chemical reaction called phosphorylation, turning acyclovir into an active compound.

Margolis thinks he knows why acyclovir did not pan out in preventing HIV: The prevention studies were trying to completely suppress herpes. "If you suppress herpes, HIV also goes down," he said. "If you suppress herpes virus completely, there is nothing to phosphorylate." Future studies would be needed to test whether lower or more infrequent acyclovir doses might be more effective, Margolis added.

A patient does not have to be infected with genital herpes to benefit, as infection with any herpes virus could work, including the nearly universal childhood infection called roseola.

Margolis said his team hopes to find better ways to use acyclovir against HIV, perhaps including it in a microbicide. Acyclovir might also be used to strengthen an HIV drug cocktail, he said.

The report, "Acyclovir Is Activated into a HIV-1 Reverse Transcriptase Inhibitor in Herpesvirus-Infected Human Tissues," was published in Cell Host & Microbe (2008:doi:10.1016/j.chom.2008.07.008).

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