March 4, 2009 -- A new kind of vaginal gel prevents sexual
transmission of the AIDS virus in
monkey studies.
The anti-HIV ingredient in the gel is glycerol monolaurate or
GML. It's already FDA approved as an ingredient in cosmetics and
medicines.
"The results are very encouraging. They point to a novel avenue
to prevent sexual transmission of HIV," study researcher Ashley T.
Haase, MD, head of the microbiology department at the University of
Minnesota, Minneapolis, said at a telephone news conference.
The surprise finding that GML can block HIV comes from basic
research showing that the AIDS virus gains a foothold in the vagina
by taking advantage of the body's immune system. Immune responses
to the virus draw T cells -- the white blood cells HIV loves to
infect -- to the site of infection. Without T-cell recruitment, HIV
loses its grip.
That's where GML comes in. The antimicrobial agent affects
immune responses and breaks the chain of events that let HIV spread
through the body.
"We thought if we could modulate the immune response at the
portal of HIV entry, we could block sexual transmission," Haase
said. "[Colleague] Patrick Schlievert's work with GML showed that
it had many properties that might block HIV expansion and
systematic spread."
Haase, Schlievert, and colleagues gave five rhesus macaque
monkeys daily GML treatments before putting 200 infectious doses of
deadly SIV -- the monkey version of HIV -- into their vaginas.
Another four animals got a gel without GML.
The four animals not given GML got AIDS. Those treated with GML
showed no sign of infection during the short-term study, although
one of the five animals showed signs of infection several months
later. But just as HIV drugs with
different modes of action are more effective when mixed into a drug
"cocktail," Haase says GML could be mixed with different kinds of
anti-HIV agents.
"GML could be part of a combined strategy with another vaginal
microbicide, such as PRO 2000, with a different mechanism of
action," he suggests.
GML is found in breast milk, Schlievert says, and it is used in
many cosmetics and in medicines taken orally or used on the
skin. And
recent studies show that GML kills many different kinds of germs --
including vaginal yeast infections and several different sexually
transmitted diseases, said Schlievert, professor of microbiology at
the University of Minnesota.
"GML is presently being considered as an additive to tampons
because of its ability to interfere with bacterial growth,
including the bacteria that cause toxic shock
syndrome," Schlievert said at the news conference.
For vaginal use in the monkey studies -- and with an eye toward
future human use -- GML was mixed with KY Warming Liquid, an
over-the-counter product widely used as a personal lubricant.
"What was done was to combine two FDA-approved medical devices
to create another approved device," Schlievert said.
However, Schlievert said GML has not yet been tested for
long-term human use.
And there's a lot more work to do with monkeys before GML gel is
ready for human tests. That will have to be done before human
studies of GML gel for HIV prevention.
Haase, Schlievert, and colleagues report their findings in the
March 4 online edition of the journal Nature.