Vaccine may slow herpes epidemic
A vaccine to prevent genital herpes has so far shown mixed results. Although it has proved ineffective in men, the vaccine has reduced transmission and outbreaks in some women whose partners have the disease.
Because immunizing even part of the population could slow the herpes epidemic, researchers are forging ahead with additional studies of the vaccine.
“It’s almost impossible to prevent the spread of genital herpes because it’s so ubiquitous,” says Charles Ebel of the American Social Health Assn., a nonprofit educational organization in Research Triangle Park, N.C. “An effective vaccine would be a significant advance.”
About one in five people older than 12 are infected with herpes simplex virus type 2 (HSV-2), which triggers genital herpes. More than half of all Americans are infected with herpes simplex virus type 1 (HSV-1), which causes cold sores.
Roughly 90% of people who are infected with genital herpes don’t know it because the symptoms can be mild. This contributes significantly to the spread of the disease, because many unwittingly pass the virus to their sexual partners. Once in the body, HSV migrates to nerve cells, where it can remain dormant for months or years at a time, triggering only occasional flare-ups. For some people, however, outbreaks can be more frequent or more painful, causing blisters, itching, burning and ulcers. But what drives scientific research on the disease is that sufferers are more susceptible to HIV infection. The herpes lesions give the AIDS-causing virus a portal of entry, says Dr. Lawrence R. Stanberry, a pediatrician at the University of Texas Medical Branch, Galveston, who administered the vaccine in recent studies. “If someone is exposed to HIV, they are two to four times more likely to become infected,” he says.
And although it is rare for babies to contract genital herpes from their mothers during the late stages of pregnancy or during childbirth, more than half of those who do will die or develop serious complications. “We’re seeing more neonatal herpes -- probably 2,500 cases a year,” says Stanberry. “If the vaccine could reduce that number by even half, that would be an incredible contribution.”
The herpes vaccine, which is made by Belgium’s Glaxo- SmithKline Biologicals, contains a piece of the outer coat of HSV-2 called a glycoprotein. This surface protein provokes the body’s immune system to swing into action, dispatching antibodies that neutralize or kill the virus. The vaccine also has a chemical, called an adjuvant, “that turbocharges the immune response” by making it attack the virus more quickly, says Dr. Robert B. Belshe, director of the Center for Vaccine Development at Saint Louis University in Missouri, one of the sites where the new vaccine is being tested.
Results were announced last year of two studies involving 2,700 men and women whose regular sexual partners had genital herpes. Among women who had neither HSV-1 nor HSV-2, the vaccine prevented disease symptoms in 73% and stopped viral transmission in 40%. It had no clear effect on women who were already infected with HSV-1 or on men.
Scientists don’t understand why this happened, says Stanberry. They speculate that in women, the presence of HSV-1 confers an immunity to the vaccine; and men don’t respond as strongly to immune system stimulation.
But even if the virus simply prevents an infected woman from developing symptoms (which means the virus isn’t shedding), it’s possible that the spread of genital herpes and HIV could still be curbed.
The new study, which is being done at 16 centers in the United States, including UCLA, will focus solely on those people who seem to respond to the vaccine -- women who are not infected with either type of virus -- to establish just how useful the vaccine may be. It will involve 7,550 women between the ages of 18 and 30; volunteers will receive three injections over six months, with a follow-up after 20 months to determine whether the vaccine works.
“If the vaccine proves effective,” says Belshe, “we’ll target pre-adolescent girls to protect them before they’re infected with either virus. Eventually, the herpes viruses will die out -- just like polio.”
*
(BEGIN TEXT OF INFOBOX)
Herpes treatments
There is no cure for herpes, but three oral medications, available by prescription, can treat HSV-2: acyclovir (Zovirax), famciclovir (Famvir) and valacyclovir (Valtrex). Each of these drugs can reduce the frequency of outbreaks and speed healing when symptoms appear. Studies have also shown that valacyclovir can reduce by 50% the risk of transmission of HSV-2 to a partner who does not have the virus.
