Researchers Discover Semen Component Increases HIV Infection

Researchers in Germany have found a factor in semen that not only aids the transmission of HIV, but actually can promote the infectiousness of the virus that causes Acquired Immune Deficiency Syndrome (AIDS). In a pre-release version of their study in the journal Cell, Frank Kirchhoff of the University of Ulm in Germany, together with Wolf-Georg Forssmann of IPF PharmaCeuticals in Hannover, Germany, and their colleagues disclose that certain peptides commonly found in seminal fluid and semen can cause a 100,000-fold increase in infectiousness.

"We found that fragments of prostatic acidic phosphatase (PAP) drastically enhance HIV infection. Functional and structural analyses showed that these peptides form amyloid fibrils that capture HIV particles and strongly enhance the number of productively infected cells by promoting virion-cell attachment and fusion," the study says.

Prostatic acidic phosphatase (PAP) is a common component of human seminal fluid, and "clumps" when found in high concentrations into amyloid fibrils, a tangle of protein fibers similar in appearance to those found in the brains of Alzheimer's victims. The function of PAP in normal reproduction is not known, and the team calls for further research in that area, since amyloid fibrils are known to be associated with a variety of human diseases.

The team of researchers found that the increase in infection was most dramatically increased when the amount of HIV was low - and similar to the levels found in sexual transmission of the disease. The research suggests that the presence of the tangles of proteins help the virus attach to the mucus lining in the genital tract, giving it a better opportunity to invade surrounding cells.

For the research, the team made use of tonsils removed during surgery to reproduce conditions resembling the vaginal tract, semen samples, and proteins separated from sperm.

Other researchers are hopeful that this discovery of one of the many mechanisms of HIV infection will lead to therapies that will prevent the spread of the disease.

"I think this is tremendous," Christopher Pilcher told the journal Nature. Pilcher is an HIV researcher at the University of California, San Francisco, who was not affiliated with the study. "It raises a lot of really fundamental questions about how HIV is transmitted."

Results of the research will be published in the journal Cell on December 28. Co-authors of the paper are: Jan Munch, Elke Rucker, Ludger Standker, Knut Adermann, Christine Goffinet, Michael Schindler, Steffen Wildum, Raghavan Chinnadurai, Devi Rajan, Anke Specht, Guillermo Gimenez-Gallego, Pedro Cuevas Sanchez, Douglas M. Fowler, Atanas Koulov, Jeffery W. Kelly, Walther Mothes, Jean-Charles Grivel, Leonid Margolis, and Oliver T. Keppler. Work was conducted in Germany, the United States, and Spain.