HIV Infection 'Drastically' Enhanced By Semen Ingredient
A plentiful ingredient found in human semen drastically enhances the ability of the human immunodeficiency virus (HIV) to cause infection, according to a report in the December 14, 2007, issue of the journal 'Cell', a publication of Cell Press.
The findings help to understand the sexual transmission of HIV and suggest a potential new target for preventing the spread of AIDS, the researchers said.
Collaborating research groups in Hannover and Ulm, Germany, show that naturally occurring fragments of so-called prostatic acidic phosphatase (PAP) isolated from human semen form tiny fibers known as amyloid fibrils.
Those fibrils capture HIV particles and help them to penetrate target cells, thereby enhancing the infection rate by up to several orders of magnitude.
"We were not expecting to find an enhancer, and were even more surprised about the strength," said Frank Kirchhoff of the University Clinic of Ulm, noting that they were initially looking for factors in semen that might help to block HIV infection. "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." [This means that a risk of transmission equals to one]
"The fibrils act like a ferry," said Wolf-Georg Forssmann of VIRO PharmaCeuticals GmbH & Co. KG and Hannover Medical School. "They pick the viruses up and then bring them to the cell."
HIV-1, the causative agent of AIDS, has infected about 60 million [believe it or not] people and caused over 20 million deaths [???], the researchers said. More than 90 percent of those HIV-1 infections are acquired through sexual intercourse. Globally, most infections result from genital exposure to the semen of HIV-positive men, earlier studies showed.
Women who acquired HIV-1 through vaginal intercourse constitute almost 60 percent of new infections in Africa. Yet the factors influencing the infectiousness of HIV in semen are poorly understood.
To identify natural agents that might play a role in sexual transmission of HIV/AIDS in the new study, the researchers sifted through a complex peptide/protein library derived from human seminal fluid in search of novel inhibitors and/or enhancers of HIV infection.
If such inhibitors can be found, they might be added to microbicide gels now under development for HIV prevention, added Kirchhoff. There could also be other ways to take advantage of the fibrils. "The high potency of SEVI in promoting viral infection together with its relatively low cytotoxicity suggests that it may not only play a relevant role in sexual HIV transmission, but could also help to improve vaccine approaches and gene delivery by lentiviral vectors," the researchers said.
Source: Medical News Today, 14/12/2007