Amyloid fibrils formed of fragments of protein found in semen boost the infectivity of the HIV virus, reports a study published this week in Nature Communications. The work outlines that naturally occurring amyloid fibrils that are present in human ejaculates can promote transmissibility of HIV.

Jan Munch and colleagues found that amyloid fibrils, formed by aggregation of specific protein fragments called amyloidogenic peptides, are present in semen of healthy individuals and can interact directly with HIV particles and increase viral infectivity. While it has been known that the amyloidogenic peptides in semen may enhance HIV transmission and that they form amyloid fibrils in cell cultures this is the first report showing that these fibrils are present in normal semen and therefore can be responsible for its HIV infectivity-boosting potential.

This study also establishes semen as body fluid that naturally contains amyloid. Insoluble amyloid deposits are commonly associated with severe disorders like Alzheimer’s disease, but, in contrast to these diseases, this work finds that seminal amyloids are present in ejaculates derived from healthy individuals.