Researchers in the US have found that a compound widely used as an anti-microbial and anti-inflammatory agent effectively blocks infection of the non-human primate version of HIV in monkeys; a step that is being heralded as a breakthrough in developing a version that works in humans to help prevent the devastating disease that affects about 33 million people around the world.

The discovery is published as an advanced access online paper in the 4 March issue of Nature. The research was led by Dr Ashley Haase and Dr Pat Schlievert, principal and co-investigator respectively in the department of microbiology at the University of Minnesota, and colleagues.

The scientists discovered that a compound called glycerol monolaurate (GML) applied as a vaginal gel stopped transmission of the nonhuman primate version of HIV, known as SIV.

It is not a cure and the drug still has to undergo trials to prove it is effective in humans. The US Food and Drug Administration recognises that it is safe and has approved it as an anti-microbial and anti-inflammatory agent in food and cosmetics.

Haase said in a press statement, "After 25 years, an effective vaccine for HIV is still on the distant horizon, so not only vaccines, but all research into ways to prevent the continued spread of this lethal virus, remain critically important. If GML as a topical microbicide can add to our prevention, it could contribute to saving millions of lives."

That scientists would be so encouraged by two animal studies and a minor success in a human trial is a sign, in part, of how stymied they have been in two decades of trying to find a microbicide or a vaccine to stem the spread of HIV.

Haase, Schlievert and colleagues applied GML as a vaginal gel to five monkeys and they also had five other monkeys as controls that were not treated with GML.

An hour later they injected the treated and untreated monkeys with an infectious dose of SIV, and four hours after that the treatment group received the GML gel again and both groups had a second dose of the virus.

The monkeys were monitored for a further two weeks: the normal progression of the virus once an animal in infected is that two weeks later, the bloodstream would contain hundreds of millions of virus particles. Monkeys showing no evidence of infection were treated again at the two week mark: the treatment group with GML and viral doses, and the control group just with the viral doses.

After receiving four large doses of the virus, none of the GML treated group showed any evidence of acute infection while five of the control group had contracted SIV.

The researchers think GML has potential as a vaginal gel to prevent HIV transmission to women, which is the route the virus now takes for most of the new cases arising throughout the world.

Haase said there was still a lot of work to be done before GML can safely and effectively be used to prevent HIV infection in women, including more animal testing, and testing dosing and delivery methods that make it easy for women to use. Longer term studies will also be needed to check for other infections that don't show themselves until months afterwards.

"The compound has been demonstrated in vitro to inhibit the growth of nearly all sexually transmitted disease microorganisms, and other causes of vaginal infections, without affecting normal bacteria. Its use by women may significantly improve overall vaginal health," Schlievert added.

In many parts of the world, it is difficult or impossible for women to refuse sex or persuade a partner to use a condom. An effective microbicide would be something that women could use by themselves.

Microbicides might also prevent infection during anal intercourse, although most studies have focused on vaginal transmission. (Also see: New 'monkey HIV' brings AIDS cure closer)