January 21 (HealthDay News) -- A topical treatment that disables genes that play a key role in the transmission of the herpes virus has been developed by U.S. researchers.

The treatment uses RNA interference (RNAi) to fight the virus in two ways: by disabling its ability to replicate and by blocking the host cell's ability to take up the virus. In mice, the treatment is effective when used from one week before to a few hours after exposure to the herpes virus.

"As far as we could tell, the treatment caused no adverse effects, such as inflammation or any kind of autoimmune response," Judy Lieberman, a professor of pediatrics at Harvard Medical School and a senior investigator at the Immune Disease Institute, said in a Harvard news release. In addition, there was no indication that the treatment interfered with normal cellular function.

The research was published in the Jan. 22 issue of the journal Cell Host & Microbe.

"People have been trying to make a topical agent that can prevent transmission, a microbicide, for many years," Lieberman said. "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 the findings can be reproduced in people, she said, "this could have a powerful impact on preventing transmission."

According to the World Health Organization, about 536 million people worldwide are infected with herpes simplex virus type 2 (HSV-2), the most common strain of this sexually transmitted disease.

Women are much more likely than men to be infected with HSV-2, and the virus can easily pass from mother to child during birth. Infants with untreated HSV-2 infection can suffer brain damage and death.

In adults, HSV-2 infection isn't life-threatening but does increase vulnerability to other viruses, such as HIV.

SOURCE: Harvard Medical School, news release, Jan. 21, 2009