Fluid mechanics of functionality of anti-HIV microbicides

Recent reports (UNAIDS, 2006) clearly demonstrate that the global HIV/AIDS epidemic presents no sign of abating; it continues to spread at a rate of 15,000 new infections every day. Today, about 42 million people live with HIV/AIDS worldwide. Among them, 25 million live in sub-Saharan Africa. In Kenya, for instance, about 2.2 million people (15% of the population) are infected with HIV. As the epidemic spreads, it is infecting more and more women; globally, it is estimated that women represent approximately 65% of all those infected with HIV/AIDS. In fact, the leading risk factor for HIV among women in much of the world is to be the monogamous wife of an unfaithful or polygamous husband. AIDS has now become one of the most serious women’s health issues globally and existing prevention methods for women at risk for HIV/AIDS are severely inadequate. Anti-HIV Microbicidal Formulations (microbicides) are a new class of products under development for prevention of HIV transmission at the sites where transmission can occur during/after intercourse. Conservative estimates are that introduction of even a partially effective microbicide could result in 2.5 million averted cases of AIDS over three years. There are now 29 microbicides under development—but none are yet on the market. Although there has been much attention to microbicides, virtually all research and development is on the active ingredients, not on the fluid delivery systems for those ingredients —i.e. the microbicide formulations (vehicles) applied by a user before sexual activity. But the vehicles are crucial: they must distribute the active ingredients to intercept HIV at all locations where it can be transmitted. Our goal is to contribute to the process of design of microbicide vehicles. We will develop a practical mathematical model of the flow of microbicidal vehicles, which can be used to study the tradeoffs in the design parameters for the microbicide vehicle, and how these affect the coating of the vulnerable vaginal surface. This relates to the level of protection of the user. The model will be applicable to microbicide vehicles now being formulated. It will be validated with experimental work of our collaborator, Prof. Katz of Duke University, whose work is funded by the NIH. We will consider how these tradeoffs interface with acceptability studies, with the advice of our collaborator Dr. Bethany Young Holt. Our efforts will produce new understanding of coating that includes both the initial distribution of vehicles after application, and also the possible changes in that coating distribution over time, as the user engages in sexual activity. For example, the coating could be dissolved or eroded away. This information will be of direct practical utility to microbicide product developers, in their efforts at effective prevention of HIV transmission.