Common Microbicide Shows Promise In Averting HIV
The relentless search for a vaginal gel to avert the AIDS virus got some good news on Wednesday, when scientists reported that a low-cost, common compound protected monkeys from a lethal variation of HIV.
However, the scientists caution that plenty of work lies ahead before the microbicide can be verified as safe and effective for humans.
Nevertheless, the outcome was embraced as an encouraging sign.
A cream that blocks or kills the human immunodeficiency virus (HIV) is a large part of efforts in the fight against AIDS. Such a cream would be particularly welcome for women in sub-Saharan Africa, who are at great risk from coercive sex from HIV-infected partners.
However, the quest has suffered many setbacks, including two trials that, disappointingly, found women who used a prototype gel ran a greater risk of HIV than those who used a placebo.
In the current study, researchers at the University of Minnesota tested a compound called glycerol monolaurate (GML), which exists naturally in the human body. The compound is licensed as an antimicrobial and anti-inflammatory agent in cosmetics and toiletries, and as a food emulsifier.
They suspected that GML interferes with immune system’s signaling processes in a way that blocks HIV’s progress at a critical stage.
When the virus enters the body, the body’s defense systems unleash a series of orders, dispatching T immune cells to the infection site. It is these T-cells that are ultimately hijacked by HIV and converted in to virus-making mini-factories, enabling the virus to proliferate throughout the bloodstream.
"Even though it sounds counter-intuitive, halting the body’s natural defense system might actually prevent transmission and rapid spread of the infection," wrote the study’s chief investigator, Ashley Haase, in a report about the study.
The team gave a vaginal application of GML gel to five rhesus macaque monkeys received a vaginal application of GML gel, and were then exposed to two large doses of simian immunodeficiency virus (SIV) — the monkey equivalent of HIV. A comparison group of five other animals that did not receive the gel also received the SIV doses.
Each dose of GML used in the experiment cost less than one US cent.
Four of the control group contracted SIV over the following two weeks, but none of the GML-treated group showed any acute infection, despite being given up to two further shots of the virus.
GML disrupts a "vicious cycle" of immune system signaling and inflammatory response in the vagina and cervix, the scientists reported.
"This result represents a highly encouraging new lead in the search for an effective microbicide to prevent HIV-1 transmission that meets the criteria of safety, affordability and efficacy," they said.
Pat Schlievert discovered GML’s use as a microbicide and anti-inflammatory when he examined toxic shock syndrome linked with the use of menstrual tampons.
He found that GML restrained the toxin-making mechanism of the germ Staphylococcus aureus, and that tampons coated with GML protected women from the bacterium and relieved vaginal inflammation.
"GML is exceptionally inexpensive, is widely used in foods and cosmetics and is easy to formulate in many ways for vaginal use," Schlievert said, adding that repeated tests have shown GML to be safe and without effect on beneficial vaginal bacteria.
Scientists reported last month the first positive trial of a microbicide known as PRO 2000, but said it reduced the risk of infection only by 30 percent, only half the minimum threshold for success.
An AFP report cited a 2003 mathematical study that found availability of a microbicide that is 60 percent effective would prevent two and a half million infections over the course of three years.
Approximately 33 million people worldwide are infected with HIIV –two-thirds of whom live south of the Sahara. And while women comprise half of all HIV-infected people worldwide, in Africa the number if nearly 60 percent.Â
The study was published in the journal Nature.
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Image Caption: GML is used in ice cream and cosmetics as an emulsifier. It is also used in soaps and chewing gum.
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