In addition to their role in drug delivery, microbicide formulations can act as physical barriers or filters to slow HIV's passage from semen into body tissues, Geonnotti explained. That slowing would give the HIV-neutralizing ingredient in the microbicide layer, as well as the body's natural defenses against HIV, more time to work. If left untreated, HIV attacks a person's immune system and can progress to AIDS, acquired immune deficiency syndrome.
The HIV pandemic continues to overwhelm current preventative measures as an estimated 12,000 people contract the infection each day, the researchers said. Increasingly, a disproportionate number of women are becoming infected. In several African countries, for example, HIV infection rates among young women between the ages of 15 and 24 are more than three times higher than among their male counterparts.
Women are about twice as likely as men to contract HIV during vaginal intercourse, according to the federal Centers for Disease Control and Prevention. In developing countries particularly, cultural and socioeconomic inequities between the sexes also can leave women more susceptible.
"In many cases, women lack control over their abilities to protect themselves against the virus," Katz said. "Microbicide development is a response to the demonstrated need for new female-controlled methods for HIV prophylaxis."
In the current study, the researchers developed a mathematical model that simulates the biological interaction between HIV contained in semen and the protective coating that accumulates on the lining of a woman's vagina after she applies a topical microbicide. The model describes the diffusion of the virus and active ingredients into the tissues, as well as the chemical inactivation of virus by the microb