Vaginal Gel Reduces HIV Risk

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A breakthrough in the fight against HIV/AIDS is being announced at the 18th International AIDS Conference—a vaginal gel for women that can significantly reduce the risk of infection with HIV (human immunodeficiency virus). The gel contains the antiretroviral drug tenofovir and is the first method of HIV prevention that women at risk of the disease through sexual intercourse can control.

Results of the Caprisa-004 study were called “a game changer” by Bruce Walker, an AIDS research at Harvard Medical School, in a Washington Post article. He noted that this was the first time women have had a tool that lets them protect themselves against the virus that causes AIDS.

The study involved 900 South African HIV-negative women who were given either the vaginal gel (1% tenofovir) or a placebo in a syringe-like applicator to use before sexual intercourse. The women were instructed to inject the gel into the vagina no more than 12 hours before intercourse and again within 12 hours after intercourse.

At the end of 36 months, there were 98 infections in the 889 women. Overall, the chance of infection was reduced by 39 percent in the women who used the gel, but among those who used it consistently and as instructed (at least 80% of episodes of sexual intercourse), the reduction was 54 percent.

Tenofovir (Viread) is used along with other antiviral medications to treat HIV in patients who have acquired immunodeficiency syndrome (AIDS). This drug is in a class of antivirals called reverse transciptase inhibitors.

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Approximately half of the 33 million people in the world who are infected with HIV are women, and in Africa, that number rises to 60 percent. Given that abstinence, using condoms, and being faithful have not been successful in preventing HIV infection, use of a vaginal microbicide gel that women can use without a man’s knowledge is a significant and critical step forward.

Six other microbicides have been tested over the past 15 years, but none of them have proven to be protective against the virus. Recently a vaginal gel composed of the antiviral compound L-870812 was found to protect female macaques from SIHV, a combination of HIV and a virus found in monkeys.

Although the results of this study are promising, the researchers note that the action of tenofovir was only one of the variables. Others included the number of sexual partners a woman had, the amount of AIDS virus in the man’s semen, the use of condoms, the prevalence of HIV infection in the male population, and the most important variable: how consistent women were in using the gel.

Therefore, at this point, investigators cannot predict how much protection the vaginal gel can provide any given woman. According to Salim Abdool Karim of the University of KwaZulu-Natal, who participated in the study, the success of the gel in preventing HIV infection “is fundamentally dependent on human behavior.”

Before the new vaginal gel can be licensed for commercial use, researchers need to demonstrate its effectiveness in at least one more group of women. One thing scientists will also likely study is why the gel wasn’t even more effective. Anthony S. Fauci, head of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, pointed out that “my most likely explanation is that you have to go up on the dose.”

Whatever the dose, the fact that this vaginal gel significantly reduces the risk of HIV infection is a breakthrough discovery, and a much awaited one.

SOURCE:
Washington Post, July 19, 2010

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