Rodent of the Week: A topical treatment for herpes not far off

Rodent of the Week: A topical treatment for herpes
2:00 PM, January 23, 2009
by Shari Roan - Los Angeles Times

Genital herpes affects about 536 million people worldwide, which means the virus really gets around. There is no cure for herpes, but oral medications exist to help prevent transmission of the virus from an infected partner to a non-infected partner. Someday, however, a highly reliable topical treatment to stop transmission may be available.

Researchers reported in Thursday's edition of the journal Cell Host & Microbe that they have created a topical treatment that prevents the transmission of herpes simplex virus type 2 (the most common strain) in mice. Moreover, the treatment, called a microbicide, prevented spread of the virus when it was applied from one week before sexual intercourse to a few hours before. Previous experimental microbicides to prevent herpes have required application just before sexual intercourse.

The study, led by Dr. Judy Lieberman of Harvard Medical School, developed a topic treatment that, in mice, disabled key genes necessary for herpes transmission. The researchers first used a natural process called RNA interference to switch off specific genes that allow the herpes virus to replicate. RNA interference occurs in the cells of multicellular organisms to regulate the translation of genetic information into proteins. Scientists have great interest in using this process to create new medications but have found it difficult to coax the RNA molecules into specific cells. Lieberman's group fused RNA with cholesterol molecules, which allowed it to be absorbed into vaginal tissues and into the cell membranes.

"People have been trying to make a topical agent that can prevent transmission, a microbicide, for many years," Lieberman said in a news release. "But one of the main obstacles for this is compliance. One of the attractive features of the compound we developed is that it creates in the tissue a state that's resistant to infection, even if applied up to a week before sexual exposure. This aspect has a real practicality to it. If we can reproduce these results in people, this could have a powerful impact on preventing transmission."

The treatment did not cause any serious side effects in mice. Lieberman recently received a grant to collaborate with a corporate partner in developing a topical microbicide for human use. She is also examining whether the same approach might be used to treat HIV infection.