Doctors at the Mount Sinai School of Medicine have tested a gel that when applied topically in the vagina, may help prevent infection by both H.I.V. and herpes simplex virus. AIDS researchers have long sought such a microbicide.

The effectiveness of the gel, called PRO 2000 and made by Indevus Pharmaceuticals, was shown in a pilot study of 20 H.I.V.-infected women. Ten were treated intravaginally with PRO 2000, and 10 with a placebo gel. An hour later, secretions were collected and examined for evidence of viral infection. The study found that the gel significantly reduced virus levels while causing no inflammatory response, and a new 14-day study is under way to test whether repeated applications will cause unacceptable side effects. A much larger study of the effectiveness of the gel has been financed and is to include more than 3,000 women at nine different sites, Dr. Keller said.

Dr. Betsy Herold [senior author of the study, professor of pediatrics and microbiology, Mount Sinai] referred to the unfortunate experience with nonoxynol-9, once believed to be protective against H.I.V. but now thought to increase the risk of viral transmission by irritating mucosal lining in men and women.

[Dr. Marla J. Keller, a professor of medicine and the lead author on the study, presented the data at the 12th Conference on Retroviruses and Opportunistic Infections in Boston on 24Feb05;  8Mar05, New York Times VITAL SIGNS, By NICHOLAS BAKALAR]