A common chemical found in food and cosmetics has been shown to protect monkeys against HIV infection, raising hopes that a similar treatment can be developed for humans.

A team of researchers has identified a compound that, when applied as a gel, appears to block the simian version of HIV from being transmitted between monkeys during sexual intercourse.

Scientists said that the chemical, which is applied in the vagina, marked an important advance in the field of microbicides – the development of creams and gels designed to prevent HIV from infecting cells.

With an Aids vaccine still decades away, there is a growing consensus that microbicides now offer the most realistic drug strategy to control the spread of the disease.

Last week The Times revealed that research into microbicides – in which Britain is a world leader – is to receive more than £90 million from the Government and the Bill & Melinda Gates Foundation over the next five years.

Aids has claimed more than 25 million lives. Of the 16,000 people around the world contracting HIV every day, the majority are infected by unprotected sex, with the greatest incidence in sub-Saharan Africa and India.

In the new study, researchers at the University of Minnesota found that glycerol monolaurate (GML) appeared to interfere with signalling processes in monkeys’ immune systems, blocking SIV – the primate version of HIV – at a key stage of potential infection.

When HIV enters the body, defence systems unleash a cascade of orders, dispatching so-called T cells to the site of the infection. These cells are then hijacked by the virus, enabling it to proliferate throughout the bloodstream.

Of the ten female rhesus macaque monkeys injected with SIV, none of the five treated vaginally with GML developed the infection – even after four large doses. Four of the five macaques without GML contracted the virus.

The paper, published in the journal Nature, concludes that GML breaks a “vicious cycle” of immune-system signalling and inflammatory response in the cervix and vagina.

“This result represents a highly encouraging new lead in the search for an effective microbicide to prevent transmission that meets the criteria of safety, affordability and efficacy,” the authors said.

Ashley Haase, the lead researcher, said that a long road lay ahead before the microbicide could be verified as safe and effective for humans but hailed the findings.

“If GML as a topical microbicide can add to our prevention, it could contribute to saving millions of lives,” he said. “Even though it sounds counter-intuitive, halting the body’s natural defence system might actually prevent the transmission and rapid spread of the infection.”

GML exists naturally in the human body and is already licensed for use in cosmetics and toiletries and as an emulsifier in foods. Each dose of GML used in the experiment cost less than a penny.

Today’s paper follows results from a preliminary trial, released last month, which suggest that another gel, PRO2000, may reduce the chances of women contracting HIV by a third. The findings – the first positive results for a microbicide – raise the prospects of success for a second, larger, trial of the same drug, run by Imperial College London, which is due to finish in August.

Describing the new monkey research as exciting, Professor Andrew McMichael, director of the Weatherall Institute of Molecular Medicine, University of Oxford, said: “This is an inexpensive compound that could be used in humans and clinical trials are very likely to follow.”

Dr Adriano Boasso, research fellow at Imperial, urged caution. “This treatment was tested on a relatively small number of animals and several years of research are still needed to determine whether this approach will eventually develop into a prospective preventive drug,” he said.

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