Researchers have shut down their human trials of the microbicide cellulose sulfate as a method to combat HIV transmission. Preliminary data found that use of the topical gel, which is applied to a woman's vagina, led to an increased risk of HIV infection.

The trials  involved 1300 women in Benin, India and Uganda and 1700 women in Nigeria. Thirty-three of the African and Indian women were infected with the virus that causes AIDS.

Vera Halpern, principle investigator of the Nigeria trails and lead scientist for Family Health International, says cellulose sulfate had been given the go-ahead after promising test results in 11 smaller trials. She expresses disappointment over the stopped trails, but says findings may offer clues for the development of a safe and effective HIV microbicide. "We just need to test other products, maybe with different mechanisms of action."

Halpern says an HIV microbicide is an important priority in the battle against HIV transmission because now the only means of prevention against the virus is either abstinence or use of a condom, a contraceptive method generally controlled by men. "We are in desperate need of a female-controlled prevention technology. We need to provide those who are affected most with a preventive tool and a topical microbicide is one of those tools -- or potentially may become such a tool."

Halpern says three other full-scale microbicide trials are underway and is hopeful at least one will yield positive results.