A study by a Montana State University researcher suggests a new avenue for developing a vaccine against genital herpes and other diseases caused by herpes simplex viruses.
In a study published earlier this year in the Virology Journal, MSU virologist William Halford showed that mice vaccinated with a live, genetically-modified herpes simplex virus type 1 (HSV-1) showed no signs of disease 30 days after being exposed to a particularly lethal "wild-type" strain of the virus.
In contrast, a second group of mice that received a more conventional vaccine died within six days of being exposed to the same "wild-type" strain.
"We have a clear roadmap for producing an effective live vaccine against genital herpes," said Halford, who works in MSU's Department of Veterinary Molecular Biology. "Although my studies were performed with HSV-1, the implications for HSV-2-induced genital herpes are clear. Overall the two viruses are about 99 percent genetically identical."
An estimated 55 million Americans carry herpes simplex virus type 2 (HSV-2), which causes genital herpes. Infection is life-long. Approximately 5 percent of those with genital herpes 2 million to 3 million Americans suffer outbreaks one to four times annually. A vaccine offering life-long protection does not exist.
The key to Halford's research was understanding how the herpes simplex virus overcame the body's natural defenses.
A cell infected with the herpes simplex virus sends a warning to neighboring cells. This warning -- an interferon response -- causes neighboring cells to enter "an anti-viral state" akin to putting on a suit of armor, Halford said.
However, herpes produces a protein, ICP0, that tricks every infected cell into destroying its own armor. Once the cell's armor is gone, the virus can propagate itself and spread to other cells, which are in turn tricked into lowering their defenses.