A specialised kind of immune cell that patrols the skin of people infected
with the herpes virus appears to prevent the outbreak of painful sores, a new
Researchers think the cells may be key to developing a potential vaccine
against genital herpes, which afflicts more than 24 million people in the United
States, according to the US Centers for Disease Control and Prevention.
How the study was done
For the study, researchers took skin samples from people infected with HSV-2,
the virus that causes genital herpes, and followed them as they healed from
Working with a high-powered microscope, researchers used fluorescent stains
to find and label different types of immune cells in the skin. They were most
interested in cells called CD8 killer T-cells.
Unlike antibodies, which bind to bacteria and viruses, preventing them from
infecting cells in the first place, CD8 cells are a second line of defense, said
Bryan Cullen, director of the Center for Virology at Duke University, in Durham,
"They kill virus-infected cells as quickly as possible after they become
infected," said Cullen, who also studies herpes infections but was not involved
in the research. Killing infected cells prevents them from becoming factories
that crank out more copies of the virus, he said.
Scientists once thought that all CD8 cells roamed the body, looking for
infected cells through the bloodstream.
By watching the immune response as it unfolded in the skin, researchers
realised that there were special CD8 cells that stayed in place, patrolling the
area around nerve endings like beat cops. They guessed that the cells were
waiting for the herpes virus to emerge and cause trouble.
To test that theory, they used very fine lasers to pluck out these
specialised cells to see what kinds of proteins they were making.
In skin that had some shedding of the herpes virus, the specialised CD8 cells
made a lot of perforin, a protein that penetrates membranes to kill cells. In
skin with no active virus, the specialised CD8 cells didn't make any perforin,
suggesting that the function of the cells is indeed to kill herpes-infected
The specialised CD8 cells also made other proteins to summon backup cells to
the site to help tamp down the attack. And they didn't seem to make chemical
signals that sound the all-clear, a message to immune responders that it's time
to leave the area, which may explain why they stick around in the skin.
"We actually showed they were a very unique population of cells," said study
senior author Dr Lawrence Corey, a virologist and president and director of the
Fred Hutchinson Cancer Center in Seattle. "They can stay in the skin for
extended periods of time, they appear to have memory, they appear to have the
kind of markers that go in response to a specific infection."
He added that doctors once thought herpes, which lies dormant in nerve cells,
would reawaken and travel up the nerve endings to the skin surface where it
would cause painful sores, and that it would take a couple of days for the body
to respond and fight off each new assault.
He said the new research shows that such outbreaks are the exception, rather
than the rule. The specialised CD8 cells in the skin seem to do a pretty good
job of keeping the virus under control.
"It seems to me that if we improve their job, and if we study them and ask
the questions - How do we give them more help? How do we make them live longer?
How do we make them function better? How do we increase their number? - we may
be able to develop an effective herpes vaccine," Corey said.
A vaccine against herpes would be a significant achievement. Aside from
abstinence, there's no surefire way to prevent herpes infections. Condoms can
reduce the risk of transmission, although the virus can still be shed from skin
areas that condoms don't cover.
Experts caution that although the new finding is promising, a vaccine is
still likely to be a long way off.
"They have good correlative evidence" that the specialised CD8 cells in skin
keep the virus at bay, Cullen said. He added, however, that the research doesn't
prove that boosting these cells would prevent infections.
He said it will take many more studies to demonstrate that - if, in fact,
"It's time to take it to the next level," Cullen said.
As for cold sores (or fever blisters) on the lips or around the mouth - also
caused by the herpes simplex virus - the researchers said that although it seems
logical that those same CD8 cells might be at work, they didn't analyse it in
To find out more about genital herpes, head to the US Centers
for Disease Control and Prevention.