Progression of HIV could potentially be slowed with acyclovir (Zovirax), a commonly available antiviral medication used to treat herpes simplex virus type 2 (HSV-2). This study is slated to be published in the medical journal The Lancet.

The findings were based on a Phase 3 trial that evaluated more than 3,000 heterosexuals in 14 sites in Africa infected with both HSV-2 and HIV.

For the randomized trial, Dr. Jairam Lingappa of the University of Washington and colleagues from around the world looked at participants randomly assigned 400 mg of acyclovir or a placebo over a course of 24 months.

For those assigned acyclovir, disease progression fell by 16 percent. In individuals whose CD4 cell count was greater than or equal to 350 cells per microliter of blood, the risk of that count falling below 350 was reduced by 19 percent.

Numbers of CD4 cells, which help the body battle infection, is a key measure of the relative health of person’s immune system.

Acyclovir is dispensed to treat HSV-2, which is more commonly known as genital herpes. Most individuals infected with HIV are also infected with HSV-2.

Dr. Lingappa cautioned that certainty about the effects of acyclovir remains elusive and that data is not in place to promote the drug as a public health intervention.

“While there is evidence in laboratory cells that acyclovir may have a direct effect on HIV,” Dr. Lingappa said, “there is currently no evidence that this is seen clinically and we found no evidence to support this in our trial.”

He does, however, recommend that patients talk to their doctors if they are concerned about flare-ups from genital herpes, which for some individuals can be quite painful.

“We know,” Dr. Lingappa said, “that herpes suppression can be helpful in suppressing the symptoms of herpes for many people, particularly those with HIV and herpes.”

Prior studies have also suggested an impact on HIV by acyclovir.

In one study, acyclovir was found to nudge HIV numbers in patients downward, although the drug did not impact HIV transmission rates (see related AIDS Beacon news).

Evaluating the drug’s impact on transmission rates was the original purpose of the last year’s study, though the unexpected impact on levels of the virus in patients’ blood suggested other avenues of potential research leading to the present study.

Researchers associated with the current study suggest that more needs to be done to link the suppression of genital herpes with a definitive reduction in HIV progression before the introduction of antiretroviral therapy, although it does represent a potentially rich vein of research.

In the short term, Dr. Lingappa sees tangible benefits related to the suppression of genital herpes within reach. “We certainly hope that this information will encourage more people who have both HIV and HSV-2 infections to consider herpes suppression and that availability of acyclovir and valacylovir will increase with associated reductions in costs around the world,” he said.

For more information, please see The Lancet (abstract) or visit ClinicalTrials.gov to learn more about the study.