Researchers Develop HIV Killing Gel

By: Ron Swerdfiger

As part of a worldwide effort to dramatically curtail the spread of the deadly AIDS virus, researchers have developed a vaginal gel designed to liquefy and release an antiviral drug when exposed to semen. The creators of the “molecular condom,” which is still in the early testing phase, claim the temperature- and pH-sensitive polymer could prove a more efficient method of delivering anti-HIV agents than typical gels and creams.

“What we hope is that by attacking the virus in semen, we can inactivate it before it has any chance of permeating the tissue,” says bioengineer Patrick Kiser of the University of Utah.

Kiser and his colleagues discovered a polymer mixture that is liquid at room temperature, but thickens into a gel-like coating at body temperature and a pH level of 4 to 5, which occurs in the vagina. The researchers designed the gel to liquefy again at neutral PH levels, because semen neutralizes vaginal PH. Kiser explains it can then mix with semen and deliver an antiviral attack, perhaps a small molecule or a polymer microbicide (microbe-killing compound).

The “molecular condom” is part of a global strategy to develop microbicides suspended in creams, gels or other materials to prevent the spread of HIV and AIDS, as well as other sexually transmitted diseases.

Clinical trials are currently ongoing for at least a dozen different vaginal microbicides, according to the Alliance for Microbicide Development.

The trick, as Kiser says, is to introduce such compounds that releases the antiviral agent as rapidly and as effectively as possible.

“It could really only take minutes for the virus to come into contact with immune system cells,” he explains, “so you don’t really have a lot of time.”

according to the study by Kiser’s group, published online December 11 by the Journal of Pharmaceutical Sciences, The molecular condom appears to be a relatively non-toxic way of efficiently delivering an antiviral drug. The researchers reported that it destroyed fewer mouse skin cells in the lab dish than two other products applied vaginally, including the routinely used spermicide nonoxynol-9.

The polymer also released 49 per cent of a small dye molecule, which is chemically similar to microbicides, within five minutes of exposure to a semen-like fluid.

However, Kiser warned that additional research is needed to determine whether the gel causes any potentially dangerous side effects like inflammation, which would attract immune cells that would increase the potential targets for the HIV virus upon exposure.

The staying power of the gel is yet to be confirmed, but Kiser says, based on its viscosity, it may remain safely in the vagina for up to a day. He understands the importance of retention time.

“If a woman has to apply a microbicide right before sex, that’s quite inconvenient,” he says.

“It’s an exciting new way to think about things,” says Polly Harrison, director of the Alliance for Microbicide Development. “We want to make these products as user-friendly as possible,” and a gel that women could apply well in advance of sex “could be a real advantage.”