Most people infected with herpes are unaware of their condition and experience either no or very mild symptoms that go unnoticed. When symptoms do occur, they typically appear as one or more blisters on or around the genitals, rectum, or mouth. The blisters eventually break and leave painful sores that may take two to four weeks to heal.

Now, scientists have identified a class of immune cells that resides in the genital skin and mucosa long-term. These cells are believed to be responsible for suppressing recurring outbreaks and symptoms of genital herpes, whether caused by herpes simplex viruses type 1 (HSV-1) or type 2 (HSV-2).

"The discovery of this special class of cells that sit right at the nerve endings where HSV-2 is released into skin is changing how we think about HSV-2 and possible vaccines," said senior author Larry Corey, M.D., Ph.D., an internationally renowned virologist and president and director of Fred Hutchinson Cancer Research Center. There is currently no effective vaccine for genital herpes.

After detecting this subtype of immune cells called CD8αα+ T cells, Corey and his co-authors, who are also scientists at Fred Hutch and the University of Washington, believe they have discovered a new foundation on which to build research for a vaccine that would prevent and treat HSV-1 or HSV-2.

"If we can boost the effectiveness of these immune cells we are likely to be able to contain this infection at the point of attack and stop the virus from spreading in the first place," explained Corey. "We're excited about our discoveries because these cells might also prevent other types of viral infections, including HIV infection."

Identifying the specific molecular targets, which are called epitopes, of the T cells is their next step in the process of developing a vaccine. A better understanding of these newly identified CD8αα+ T cells may also play a critical role in creating effective vaccines against other types of skin and mucosal infections, according to Corey.

Nationwide, 16.2 percent of the population, or about one out of six people, aged 14 to 49 have genital HSV-2 infection. Centers for Disease Control and Prevention (CDC) estimates that, annually, 776,000 people in the U.S. get new herpes infections. Although an antiviral treatment is available, it's ineffective in terms of transmission of the infection from one person to another.

Over the past decade, the percentage of people with genital herpes infection has remained stable. Transmission from an infected male to his female partner is more likely than from an infected female to her male partner. Because of this, genital HSV-2 infection is more common in women (approximately one out of five women aged 14 to 49) than in men (about one out of nine men aged 14 to 49).

"Newborn herpes is one of the leading infections transmitted from mothers to children at the time of delivery," said Corey. "An effective genital herpes vaccine is needed to eliminate this complication of HSV-2 infection."

The research used novel technologies to examine the T cells in human tissues and also performed unique studies in humans. The results speak for themselves.

"The cells we found perform immune surveillance and contain the virus in the key battlefield where infection occurs, which is the dermal-epidermal junction," said Jia Zhu, Ph.D., corresponding author, research assistant professor in laboratory medicine at the University of Washington and an affiliate investigator in the Fred Hutch Vaccine and Infectious Disease Division. The dermal-epidermal junction is important because of the roles it plays in cellular communication, nutrient exchange and absorption, and other skin functions.

"We did not expect to find CD8αα+ T cells in the skin," said Zhu. "This was a surprise."