Immune cells that suppress genital herpes infections identified
Discovery has implications for development of a vaccine to prevent and treat HSV-2 and similar infections
SEATTLE - May 8, 2013 - Fred Hutchinson Cancer Research Center and
University of Washington scientists have identified a class of immune cells that reside long-term in the genital skin and mucosa and are
believed to be responsible for suppressing recurring outbreaks of genital herpes. These immune cells also play a role in suppressing
symptoms of genital herpes, which is why most sufferers of the disease are asymptomatic when viral reactivations occur.
The discovery of this subtype of immune cells, called CD8aa+ T cells, opens a new avenue of research to develop a
vaccine to prevent and treat herpes simplex virus type 2, or HSV-2. Identifying these T cells' specific molecular targets,
called epitopes, is the next step in developing a vaccine.
The findings are described in the May 8 advance online edition of Nature .
Better understanding of these newly identified CD8aa+ T cells may also play a critical role in developing effective vaccines
against other types of skin and mucosal infections, according to senior author Larry Corey, M.D. , an
internationally renowned virologist and president and director of Fred Hutch.
"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 Corey. "For the first time, we know the type of immune cells that the
body uses to prevent outbreaks. We also know these cells are quite effective in containing most reactivations of 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. We're excited about our discoveries because these cells might also
prevent other types of viral infections, including HIV infection."
There is currently no effective vaccine for genital herpes. "While antiviral treatment is available, the virus often
breaks through this barrier and patients still can transmit the infection to others," Corey said. "In addition, newborn
herpes is one of the leading infections transmitted from mothers to children at the time of delivery. An effective genital
herpes vaccine is needed to eliminate this complication of HSV-2 infection."
The long-term persistence of CD8aa+ T cells where initial infection occurs may explain why patients have asymptomatic
recurrences of genital herpes because these cells constantly recognize and eliminate the virus, according to 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 cells we found perform immune surveillance and contain the virus in the key battlefield where infection occurs, which
is the dermal-epidermal junction," said Zhu. "These cells are persistent in the skin and represent a newly discovered phenotype
distinguished from those of CD8+ T cells circulating in the blood."
The dermal-epidermal junction (DEJ) is where the dermis (the tissue layers just beneath the skin) connects to the
epidermis (outer skin layer). This junction is important because of the roles it plays in cellular communication, nutrient
exchange and absorption, and other skin functions.
Scientists examined the DEJ for T cell activity because this is where the genital herpes virus multiplies after reactivating
and traveling from its hiding place in the body's sensory neurons. Previous research by the same research group showed that the nerve
endings reach the dermal-epidermal junction and release the virus that infects the skin and can cause lesions.
Prior to this research, CD8aa+ T cells were known to exist in the gut mucosa. Much of the research on CD8+ T cells has
focused on studying them in the circulating blood, which has a dominant phenotype of CD8aß+. Fred Hutch and UW scientists compared
the two types of CD8+ T cells and found that only the CD8aa+ T cells persist in the skin while CD8aß+ T cells diminished from
the tissue after healing of a herpes lesion.
"We did not expect to find CD8aa+ T cells in the skin," Zhu said. "This was a surprise."
The research involved using novel technologies to examine the T cells in human tissues. In all, the work provides a
roadmap that can be applied to other human diseases, according to Zhu.
Zhu said the studies the research group performed in humans are unique. "To our knowledge, we are the only research group to
use sequential human biopsies to study CD8+ T cell function in situ, in their natural spatial distribution and at their original
physiological state," she said.
According to the federal Centers for Disease Control and Prevention, 776,000 people in the United States are newly
infected with herpes annually. Nationwide, 16.2 percent, or about one out of six people aged 14 to 49 years have genital HSV-2
infection. Generally, a person can only get HSV-2 infection during sexual contact with someone who has a genital HSV-2
infection. Transmission can occur from an infected partner who does not have a visible sore and may not know that he or she is infected.
Most individuals infected with HSV-2 or the related HSV-1, which causes genital herpes and cold sores, experience either
no symptoms or have very mild symptoms that go unnoticed or are mistaken for another skin condition. Because of this, most people
infected with HSV-2 are not aware of their infection.
Grants from the National Institutes of Health and the James B. Pendleton Charitable Trust funded the study. Researchers
from the University of Washington and the Benaroya Research Institute also contributed to the study.
Editor's note: Please contact Dean Forbes in Fred Hutch media relations to schedule interviews with a study author.
To obtain a copy of the Nature paper, "Immune surveillance by CD8aa+ skin-resident T cells in human herpes virus infection,"
please contact the Nature press office or contact Jenny
Chapman, Jenny.Chapman@nature.com
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Fred Hutchinson Cancer Research Center
At Fred Hutchinson Cancer Research Center , home to three Nobel laureates,
interdisciplinary teams of world-renowned scientists seek new and innovative ways to prevent, diagnose and treat cancer, HIV/AIDS
and other life-threatening diseases. Fred Hutch's pioneering work in bone marrow transplantation led to the development of
immunotherapy, which harnesses the power of the immune system to treat cancer with minimal side effects. An independent,
nonprofit research institute based in Seattle, Fred Hutch houses the nation's first and largest cancer prevention
research program, as well as the clinical coordinating center of the Women's Health Initiative and the
international headquarters of the HIV Vaccine Trials Network. Private contributions are essential for enabling Fred Hutch scientists to explore novel research opportunities that lead to important medical breakthroughs. For more information visit www.fredhutch.org or follow Fred Hutch on Facebook , Twitter or YouTube .
MEDIA CONTACT
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Source: Fred Hutchinson Cancer Research Center
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