A new type of treatment has been found to protect mice against a nasty strain of herpes virus common in humans. Because this genital virus is an important co-factor for the transmission of AIDS, the discovery could lead to inexpensive protection against the ongoing epidemic that will kill more than 3 million people this year.
“In the United States, approximately 20 percent of the population are infected with HSV-2 (herpes simplex virus 2),” says Deborah Palliser of Harvard Medical School. “Each year around 1 million more cases occur. In sub-Saharan Africa, the infection rate is about 80 percent. For all these people, there is a threefold increased risk of also becoming infected with HIV [the virus that causes AIDS].” In 2005, some 5 million people developed AIDS, bringing the total number of people living with the disease to more than 40 million worldwide.

At Harvard’s CBR Institute for Biomedical Research, Palliser and her colleagues put small amounts of genetic material known as small interfering RNA (siRNA) into the vaginas of mice. Such molecules can suppress the activity of disease-causing genes.

Mice given siRNAs that block the genital herpes survived after being challenged with lethal doses of the virus. Those given siRNA not active against the virus did not.

The herpes virus is not fatal in humans, but it causes chronic infection and genital ulcers that dramatically increase the risk of infection by HIV and other viruses. In humans, the siRNA would be applied to inside and outside genital surfaces.

“The siRNA could either be administered to a person already infected to reduce viral shedding, pain, and transmission to a sexual partner, or it could be administered to those who are not infected to protect them,” says Judy Lieberman, professor of pediatrics at Harvard Medical School and director of the Division of AIDS at the CBR Institute for Biomedical Research.

The story of this research was first told on the Web site of the journal Nature on Nov. 23, and it will be printed in a later edition of that scientific magazine. Authors of the report include David Knipe, Higgins Professor of Microbiology and Molecular Genetics at Harvard Medical School, who first identified the genes necessary for the herpes virus to reproduce, the genes silenced by the siRNAs.