A Johns Hopkins University team has devised a microbicide that not only prevents STDs such as AIDS but also acts as a contraceptive. The mechanism of the odorless ointment, called BufferGel, is based on simple chemistry: Alkaline compounds neutralize acid -- and other chemicals can reverse that process. The vaginal area is mildly acidic, with a pH level of four (neutral is seven), comparable to the acidity of wine. "That degree of acidity kills sperm, and all sorts of germs," said Richard Cone, a biophysicist at Hopkins who helped develop BufferGel.

Semen, with a pH between seven and eight, raises the vaginal pH to seven for hours. This allows sperm to survive long enough to fertilize an egg, but enables germs to infect cells. Based on this effect, researchers devised a strategy that mimics the vagina's natural defenses. Researchers found a pharmaceutical compound used to thicken ointments was able to preserve vaginal acidity even in the presence of sperm, so they made it into a lubricant gel. "We wanted to use something that had a long track record of safety with no side effects," said Dr. Thomas Moench, a co-developer of the gel.

Initial tests, conducted in the early '90s, indicated BufferGel preserved the acidity of the vagina, killing such STDs as HIV, gonorrhea, chlamydia, herpes, syphilis, HPV and trichomoniasis, the most common STD. Safety studies on 125 women in the United States and abroad were recently completed. A contraceptive trial by the National Institutes of Health is underway in which 975 women will use a diaphragm with either BufferGel or a conventional spermicide. If all goes well, BufferGel could hit US markets in two years.

The more crucial test, say researchers, will begin in the spring, when 8,500 women in the United States, India and Africa will see if BufferGel can thwart HIV. If it is effective, it will provide an alternative to women whose partners refuse to use condoms. "This puts the control back into a woman's hands," said Cone.

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