An unexpected discovery in a herpes lab might bring relief to cancer patients.
At Fred Hutchinson Cancer Research Center, the husband–and–wife team of Drs. Tao Peng and Jia Zhu for years has been carefully picking apart the molecular mechanics of herpes simplex virus type 2 (HSV–2). Their goal is a better understanding of its maddening cycles of dormancy and reactivation.

Three years ago, their attention was drawn to a small protein known as interleukin–17c, which they found is churned out by skin cells under assault by HSV–2. Perhaps, they thought, the skin cells were using IL–17c to fight off these infections. If so, they might have stumbled upon a new way to block herpes, including HSV–1, which causes cold sores.

In test after test, however, this seldom–studied protein showed no antiviral effect whatsoever.

But the scientists were too curious to give up on IL–17c. They wondered: Why were these skin cells making so much of the stuff, and what was it doing?

What they eventually found astonished them: IL–17c was stimulating the growth of nearby sensory nerve fibers, and the herpes virus itself was goading skin cells to produce it.

Human herpes simplex viruses infect and destroy skin cells, but then they retreat far from the infection site and lie dormant inside bunches of nerve–cell bodies called ganglia. When reactivated, they use the long fibers of nerves to move about. IL–17c appears to operate as a chemical signal that protects and promotes the growth and branching of peripheral nerves. The herpes virus, in a sense, wants to keep those fibers healthy, because they are the roads these viral particles travel in search of new skin cells to infect.

Think of IL–17c as the chief of a road crew, directing construction and upkeep of the highways herpes viruses take on their way to mayhem.

These viruses are ancient, believed to have co–evolved with human beings over millions of years. Somewhere on that evolutionary path, herpes simplex may have learned to orchestrate nerve repair.

In a paper published in the Journal of Experimental Medicine, the couple and their mentor, Dr. Larry Corey —president and director emeritus of Fred Hutch — report on their discovery that IL–17c appears to be a neurotrophin, a nerve growth factor. Although the human body can produce up to 1 million different kinds of proteins, only a handful have been shown to promote nerve growth. Now, there is a new one on the list.

That serendipitous discovery has opened the door to exciting possibilities.

“Hopefully, we’ve found a substance that naturally repairs neurons — that does it silently, every day, in every human being on Earth,” said Corey, who heads the laboratory in the Hutch’s Vaccine and Infectious Disease Division where Peng and Zhu did their IL–17c research. “If that is truly what its main function is, and we can harness that function, we’re going to do something good for people.”