The virus that causes herpes could one day provide relief, rather than misery. In today Proceedings of the National Academy of Sciences , biologists show that the herpes virus can shuttle human genes in nerve cells in mouse pain, increasing their tolerance to pain. If the technique works in people, it could be used to relieve chronic pain.
pharmacologist Steven Wilson at the University of South Carolina, Columbia, and molecular geneticist Joseph Glorioso of the University of Pittsburgh sought to exploit the herpes virus tends to take residence in sensory neurons. First, the duo removed pieces of several genes of the virus to prevent it from causing disease. They also attached to a human gene that produces the pro-enkephalin, a peptide of natural pain blocking, and a second gene that produces a blue dye, to trace the path of the virus under the microscope. They were then infected mice with the modified virus.
To determine how the treatment affected mice, David Yeomans, University of Illinois, Chicago, watched how they reacted to a pain test standard. Mice get their away leg of a heat lamp in about 12 to 15 seconds, but they feel pain and yank back much more quickly after being sensitized by capsaicin, the active ingredient in hot peppers. Capsaicin stimulates the nerve cells that also cause chronic burning pain in humans. The sensitizing effect "was completely abolished by the virus," says Wilson. Infected mice withdrew their paws again - proving that they could feel the normal sensations of pain -., But the hypersensitivity of chronic pain was past
"This is the first evidence that genes neuropeptides delivered in this way can actually have an effect on pain, "says Gudarz Davar, an anesthesiologist at Brigham and Women's hospital in Boston, Massachusetts. Davar is "cautiously optimistic" that gene therapy will eventually be used to control pain in people. Before that happens, he said, researchers need to show it works in animal models that more closely mimic human disease. They must also ensure that the herpes virus mails can not go back to the enemy by friends "recombine" with active herpes virus hides in the body.
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