The idea of developing a topical gel to prevent the sexual transmission of HIV isn't new: It may have first been proposed 15 years ago. But there have been significant steps forward, and Pittsburgh researchers are among leaders in the field.
Pittsburgh is the epicenter of research into "microbicides" -- topical substances that prevent the sexual transmission of HIV when applied to the vagina or rectum. Since 2006, the University of Pittsburgh and Magee-Women's Research Institute have been the base for the Microbicide Trials Network. The global research effort has been conducting studies in the U.S., India, Malawi, Uganda, South Africa, Zambia and Zimbabwe.
Early on, researchers focused mostly on gels that could be used vaginally. But as the network's co-principal investigator, Dr. Ian McGowan, notes, "It was apparent to some [researchers] then, and more people now, that both men and women have anal sex."
Which is often where the risk lies. The protective layer in the vagina, McGowan says, is 20-30 cells to thick. In the rectum, there is only one cell between the interior and the tissue where infections start.
In an important step forward last year, a major study showed that one microbicide, tenofovir gel, was found to prevent HIV in women when used vaginally.
While the results were exciting, McGowan says "it wasn't a home run." HIV-transmission risk was reduced by only 39 percent in women.
Still, that partial success was enough to hasten research efforts. Trials are being conducted now at Pitt and Magee, as researchers search for the optimal concentration and use of microbicides.
And with colleagues in Los Angeles, Pittsburgh researchers are pioneering a technique called "explanting," in which tissue is taken from participants who use the gel. Scientists then test the gel's effectiveness by trying to infect the treated tissue with HIV in a test tube.
McGowan and his colleagues are eyeing big things for 2011 -- including data expected from two other major research projects. One study examines a new formula of tenofovir. In another, researchers will learn what level of drug concentration is safe and acceptable when the drug is given orally or rectally, and where they differ in preventing the disease.
Such a study, says McGowan, "really gives us the building blocks we need to plan more advanced studies."
Editor's note: An earlier version of this story misstated the nature of one experiment on tenofovir's effectiveness among gay men.