Scientists believe they are a step closer to understanding how to block HIV transmission between men and women. A US and Swiss team used an experimental drug to protect monkeys from their equivalent of the virus.

It appeared to stop transmission across the vagina by binding with a cell surface molecule called CCR5 to prevent the virus infecting other cells.

The authors told journal Science their work was in its early stages and no such drug was yet available for humans.

Lead researcher Dr Michael Lederman, from the University Hospitals of Cleveland Centre for Aids Research, in Ohio, said: “We have identified a potential target that may offer a simple strategy for preventing HIV.”

It is known that HIV can be transmitted between men and women at mucosal sites such as the vagina.

The virus uses certain cell surface molecules to get into cells and infect them.

One of these is called CCR5 and it had already been shown that people who lack this surface molecule on their cells are almost completely protected from acquiring HIV.

But HIV can use other target molecules to get into cells.

Dr Lederman’s team set out to investigate whether blocking CCR5 would be enough to prevent simian HIV (SHIV) transmission.

They coated the vaginal surfaces of macaque monkeys with an experimental drug that would bind with CCR5, thereby making this surface molecule unavailable to SHIV.

The experimental drug, which is a modified version of a natural human protein called RANTES, protected the monkeys from SHIV infection.

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