University of Minnesota researchers in Minneapolis say that a microbicide gel made from glycerol monolaurate, an ingredient in some foods and cosmetics, has shown some promise in protecting female monkeys from contracting an HIV-like virus.
Ashley Haase, an immunologist at the university, has revealed that the compound may act by suppressing an unfortunate immune response that helps the virus rather than fights it.
He points out that other candidate microbicides cripple the virus itself, or its interactions with its favoured target - immune cells called CD4+ cells.
However, while characterizing the earliest stages of infection, Haase's team found how and when the immune system recruits more CD4+ cells to the site of infection - a response that helps the virus to spread.
The researcher thinks that inhibiting this immune response may help stop the virus in its tracks.
"It is a new idea and sort of counterintuitive. You would think we should induce the innate immune response.
But it turns out these viruses have not only learned to live with that immune response, they relish it," Nature magazine quoted him as saying.
Early stages of HIV infection are difficult to study in humans because the time of initial infection is often not known, which is why Haase and his colleagues looked at a related simian immunodeficiency virus (SIV) in female rhesus macaques.
They monitored the small population of CD4+ cells that are initially infected in the cervix and vagina, and then watched as more of the cells arrived and expanded the site of infection.
The team also found that the immune system generated several proteins during the first few days of infection, which have previously been shown to attract CD4+ cells.
Haase revealed that that observation reminded him o f work done by a fellow immunologist at the University of Minnesota, Patrick Schlievert, whose lab had found that glycerol monolaurate inhibits the production of some deadly bacterial toxins, including anthrax toxin and toxins responsible for toxic shock syndrome.
The researcher added that the compound also inhibits some immune responses to a toxic shock syndrome toxin.
Thus, Haase and his colleagues decided to mix glycerol monolaurate with a gel, and test its ability to block SIV infection in the macaques.
Two weeks later, four of the five control monkeys that were treated with the gel alone were infected with the virus.
The researchers said that none of the monkeys treated with glycerol monolaurate showed evidence of infection in the first two weeks, although one of them did later develop an infection.
The team also observed that the monkeys treated with glycerol monolaurate lso produced less Mip-3a than the control animals, suggesting that the treatment reduces the immune response that helps HIV to spread.
Although the results of this study seem promising, some researchers are not in favour of taking glycerol monolaurate into human trials.
They point out that the compound is a surfactant, and that previous trials with another surfactant not only failed to protect women from HIV, but increased their risk of infection.
"At the moment, the jury would be quite sceptical of a surfactant. This product would have an uphill path to get to the clinic," says Ian McGowan, an immunologist at the University of Pittsburgh School of Medicine in Pennsylvania who has studied microbicides as a principal investigator in the Microbicide Trials Network.
Haase, however, insists that his safety studies have thus far shown no evidence that glycerol monolaurate causes damages like inflammation and lesions in the vagina and cervix.