Vaginal Gel Blocks HIV, Herpes

A vaginal gel has strong HIV- and herpes-blocking action even an hour after use.

The gel is PRO 2000, now in large-scale clinical tests. It's hoped that the odorless, colorless product — what scientists call a vaginal microbicide — will slow the spread of HIV and other sexually transmitted diseases.

The new findings come in a report by Mount Sinai School of Medicine researcher Marla Keller, MD, at this week's 12th Conference on Retroviruses and Opportunistic Infections in Boston.

"There is an urgent need for the development of safe and effective vaginal microbicides," Keller says, in a news release. "While condoms offer protection against sexually transmitted infections, their effectiveness is limited because they require partner initiation or consent."

A vaginal microbicide thus offers women a way to protect themselves against HIV and STDs, even if their sex partner refuses to use a condom.

Keller's team randomly gave PRO 2000 — or an identical gel with no active ingredient — to 20 women with HIV infection. An hour later, they collected vaginal fluids from each of the women. In lab studies, they tested whether these vaginal fluids could prevent HIV or herpes infection of human cells.

PRO 2000 treatment made it nearly 1,300 times harder for HIV to infect cells — nearly 500 times better than placebo. PRO 2000 also made it 2,600 times harder for herpes simplex virus (search) to infect cells — about 260 times better than placebo.

And there's more good news: A microbicide won't do much good if it causes inflammatory responses that make vaginal tissues redden and swell. Analysis of PRO 2000-treated fluids showed no sign of the chemical messengers that trigger these unwanted responses.

The U.S. National Institute of Allergy and Infectious Diseases recently announced the start of a large trial testing PRO 2000 and another vaginal microbicide, BufferGel. Unlike PRO 2000, which contains a virus-blocking agent, BufferGel boosts the vagina's natural acidity, which hinders the ability of the virus to infect cells. The 2.5-year trial will take place in Philadelphia, South Africa, Malawi, Tanzania, Zimbabwe, and Zambia.

PRO 2000 is made by Indevus Pharmaceuticals, in Lexington, Mass. BufferGel is made by ReProtect Inc., in Baltimore, Md.

By Daniel J. DeNoon, reviewed by Michael W. Smith, MD

SOURCES: Keller, M. 12th Conference on Retroviruses and Opportunistic Infections, Boston, Feb. 22-25; abstract 535. News release, Mount Sinai School of Medicine, Feb. 24, 2005. News release, NIAID, Feb. 11, 2005.