July 9, 2008
Women who use microbicides in an effort to protect themselves from HIV could end up with fewer treatment options if they contract the virus because of possible drug resistance, according to a study published Monday in the Proceedings of the National Academy of Sciences, Reuters reports.
For the study, Sally Blower of the University of California-Los Angeles and David Wilson of the University of New South Wales used data from ongoing trials of microbicides, along with what is known about how HIV develops resistance to existing medicines and how consistently people use drugs and condoms. If an eventual microbicide was not 100% effective and if women did not use it consistently, then a certain percentage of women could contract HIV, according to the researchers' model. Some of these women would continue using the microbicide but not adhere to antiretroviral combination therapies and, thus, would develop resistance, the researchers said (Fox, Reuters, 7/8). According to Blower, trials that remove HIV-positive women most likely will not show how a microbicide could contribute to resistance. "Ethically, it's a good strategy to take infected women out of the microbicide trials," Blower said, adding, "But when you use microbicides as a public health intervention, some women will get infected without being diagnosed and will probably develop resistance to the drug in the microbicide" (Bloomberg/Long Island Newsday, 7/7).
According to Blower and Wilson, drugs used in a microbicide can be absorbed into the body through the vaginal wall and could cause HIV to mutate. They added that this is possible especially in circumstances when people such as commercial sex workers fail to regularly use microbicides (Reuters, 7/8). In addition, prevention trials that halt the use of microbicides for women who have become HIV-positive could allow risky products to enter the market, the researchers said.
Rowena Johnston, director of research for the American Foundation for AIDS Research, said the study's findings are particularly "disturbing" for low-income countries, where there are few options for HIV/AIDS treatment. HIV-positive people who develop resistance may have few other affordable options, Johnston said, adding, "Finding an effective microbicide is going to be challenging enough. We don't want to compound that with the possibility of creating drug resistance." According to Johnston, trial researchers could use microbicides that contain drug combinations that would not promote the development of resistant HIV strains (Bloomberg/Long Island Newsday, 7/7).
The researchers also found that microbicides, which typically are aimed at protecting women from HIV, could be equally or more effective at protecting men. According to computer models used in the study, if and when microbicides are perfected, they could reduce the risk of men contracting HIV from women. "Paradoxically, although microbicides will be used by women to protect themselves against infection, they could provide greater benefit to men," the authors wrote. Because drug-resistant HIV often is less likely to be transmitted from one person to another, male sex partners of women who have developed resistance related to microbicide use might still be protected from the virus, according to Blower (Reuters, 7/8).
An abstract of the study is available online.
Reprinted with permission from kaisernetwork.org. You can view the entire Kaiser Daily HIV/AIDS Report, search the archives, or sign up for email delivery at www.kaisernetwork.org/dailyreports/hiv. The Kaiser Daily HIV/AIDS Report is published for kaisernetwork.org, a free service of the Kaiser Family Foundation, by The Advisory Board Company. © 2008 by The Advisory Board Company and Kaiser Family Foundation. All rights reserved.