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Nature.com:

Semen boosts HIV transmission

Fibres may be more important than viral load in determining transmission rates.

Heidi Ledford

It's not just viral load in semen that matters: other compounds can boost HIV infectiveness.DigitalVision

A component found in semen can enhance HIV transmission by as much as 100,000-fold, researchers have found. The results, if verified in a clinical setting, could identify a new way to help prevent the spread of the disease.

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Now researchers have found that peptides clustered together into long fibres may be more important for HIV transmission than viral load. “If that’s true, then we’ve been looking at the wrong thing for a long time,” says Pilcher.

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They found that fragments of a protein called 'prostatic acidic phosphatase' strongly enhanced HIV transmission. The peptides were most active when they clustered together to form fibres called amyloid fibrils.

Depending on the laboratory assay being used, the fibres enhanced transmission of the virus by as little as 30-fold or as much as 400,000-fold. The results are published this week in Cell ¹. The researchers also tested the fibres in rats that were engineered to be susceptible to HIV infection. Rats injected with both the fibres and HIV had five times more viral DNA in their blood than those injected with HIV alone.

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Many human proteins can form amyloid fibrils, and these fibres are associated with several diseases including Alzheimer’s disease, Parkinson’s disease and diabetes. But none had been previously shown to affect virus transmission, says Per Westermark, who studies the fibrils at Uppsala University in Sweden.