Scientists uncover infective HIV protein

Researchers from Germany have identified a protein found in human semen which they believe may actually help the HIV virus to infect cells.

Writing in the journal Cell, the team said that the discovery could help to explain the sexual transmission of the disease, as well as providing a potential new target for preventing its spread.

They found that fragments of prostatic acidic phosphatase (PAP), an enzyme produced by the prostate, formed in tiny fibres known as amyloid fibrils, which helped HIV particles to penetrate cells enhancing the infection rate by up to 100,000 times in certain conditions.

"We were not expecting to find an enhancer and were even more surprised about the strength," said Frank Kirchoff, of Ulm University. "Most enhancers have maybe a two- or three-fold effect, but here the effect was amazing - more than 50-fold and, under certain conditions, more than 100,000-fold.

"At first I didn't believe it, but we ran the experiment over and over, always with the same result," he added, explaining that the team had originally been looking for factors in semen that might help block the spread of HIV, before stumbling upon the discovery.

More than 60 million people have been infected by HIV around the world, 20 million of whom have died. According to the researchers, some 90 per cent of infections are acquired from sexual intercourse.

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