WASHINGTON Gels aimed at helping women protect themselves from the AIDS virus may end up helping men as much or more, researchers predicted on Monday.
Computer models predict that if and when such gels or creams are perfected, they would reduce the risk that men could get the incurable virus from women.
But women who use such gels, or microbicides, could end up with fewer treatment options if they do become infected with HIV anyway, said Sally Blower of the University of California, Los Angeles, and David Wilson of the University of New South Wales in Sydney, Australia.
"Paradoxically, although microbicides will be used by women to protect themselves against infection, they could provide greater benefit to men," they wrote in the Proceedings of the National Academy of Sciences.
A microbicide is a gel or cream that could be applied vaginally or rectally to protect against sexual transmission of the human immunodeficiency virus that causes AIDS.
None are on the market now, although several are being tested. Two versions use HIV drugs such as tenofovir which is usually taken orally to suppress the virus.
Blower and Wilson wanted to see if women risked developing resistance to such drugs if they used a microbicide but got infected anyway. Their idea is that the drugs can be absorbed into the body through the vaginal wall and then, like any other drug, could cause the AIDS virus to mutate.
Blower said their mathematical models predicted this was indeed possible, especially under real-world circumstances when some people like sex workers might not use the products consistently.
"What we found out that was interesting or surprising or paradoxical, was that under some conditions males would actually benefit a lot more than females," Blower said in a telephone interview.
"You would actually prevent a lot more infections in men than in women. That was surprising."
For their models Blower and Wilson used data taken from ongoing trials of microbicides, along with what is known about how HIV develops resistance to existing drugs and how consistently people use drugs and condoms.
If an eventual microbicide was not 100 percent effective, and if women did not use it consistently, then a certain percentage of women would get HIV anyway. Some of these women would continue using the microbicide but not take cocktails of HIV drugs, and so would develop resistance.
Often, drug-resistant HIV is less likely to be transmitted from one person to another, Blower said. So male sex partners of such women might be protected from HIV.
An estimated 33 million people have HIV, mostly in Africa. More than 61 percent of Africans with HIV are women who were infected by their husbands or other male sexual partners.
Most of the 3 million people who get HIV every year globally are women.
Condoms prevent infection but many men refuse to use them. Experts say women, and some men, need a private way to protect themselves.
"At the moment, there is absolutely nothing that women can do to protect themselves from HIV -- condoms are not in women's control," Blower said.
(Editing by Alan Elsner)