Therapeutic vaccine fights herpes.

Typically, vaccines help people ward off microbial threats. Now, researchers have developed a vaccine that may be useful for treating people already infected.

The new, therapeutic vaccine reduces the frequency with which genital sores appear in patients infected with the herpesvirus. While it fails to outperform the existing antiherpes drug, acyclovir, it sets the stage for a more effective treatment in the future, scientists report in the June 11 LANCET. Over 25 million people in the United States are infected with the virus, which stays in the body for life.

"The ability to influence the frequency of genital herpes outbreaks with this vaccine inspires optimism that similar successes may be possible with other chronic viral diseases, such as AIDS," assert Stephen E. Straus of the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Md., and his colleagues.

"It's unbelievably exciting," says Lawrence R. Stanberry of the University of Cincinnati College of Medicine. These findings may help researchers treat other diseases with long incubation periods, he adds.

Other investigators have claimed to develop therapeutic vaccines, but their products have not withstood carefully controlled studies, Straus says.

Researchers at the University of Washington in Seattle and at NIAID injected either the vaccine or a placebo into 98 men and women age 18 to 55 who annually experienced 4 to 14 outbreaks of herpes simplex virus type 2 (HSV-2). They gave the shots at the beginning of the study and again 2 months later.

The vaccine is a combination of alum and a genetically engineered protein, glycoprotein D (gD2), which sits on the outside surface of HSV-2 and is targeted by the body's immune cells, Straus explains. The alum acts as an adjuvant, enhancing the body's defensive mechanisms. Alum also served as the placebo.

During the 1-year study, volunteers receiving gD2 had about one-third as many herpes outbreaks as those getting the placebo. Also, vaccine recipients had a lower median number of annual recurrences -- four versus six for those receiving alum alone. Overall, the placebo group had a total of 321 outbreaks, 74 more than the vaccine cohort.

The vaccine increases the body's production of antibodies to the herpes protein, the researchers note, whereas recurrence of genital herpes does not. "[The] vaccine boosted neutralizing antibodies to HSV-2 fourfold and gD2-specific titers sevenfold over baseline levels," they state. But the increases failed to explain the vaccine's success, since they did not seem to affect the frequency of outbreaks. Just how the vaccine helps remains unclear.

Limited use of acyclovir did not alter the vaccine's efficacy

Straus' group is halfway through a follow-up study of additional patients, using a new vaccine "that we think may do a lot better," he says. It uses two recombinant proteins from the herpes-virus and a much more potent adjuvant. Straus expects the study will be completed in about 2 years.