Turning Off TB

About one-third of the world's population carries the tuberculosis bacterium in their bodies, and about 3 million people die of tuberculosis each year. Yet scientists are just beginning to understand TB on the genetic level.

Illustration by Lydia Hess.In June, UW Pathobiology Professor David Sherman announced that he was able to interrupt the function of a TB gene that allows the bacterium to go dormant. Sherman suspects the disrupted bacterium may not be able to mount a defense against the body's immune system.

"Interrupting that process," Sherman says, "could provide a powerful new weapon in the fight against this ancient and deadly scourge."

Ninety percent of the people carrying the bacterium may test positive for it, but will never develop the active form of the disease. The body's normal response to TB infection is to encapsulate the bacterium in a soft mass of tissue called a granuloma. Within the low-oxygen environment of the granuloma, scientists believe that the bacterium enters a dormant state.

Sherman's laboratory research shows that if a gene vital to the early stages of the granuloma adaptation is turned off, the genetic response of the organism is interrupted. His paper, published in the June 19, 2001 edition of the Proceedings of the National Academy of Sciences, may point the way for an effective future treatment of tuberculosis.

"No one in the world so far can afford to be complacent about this disease," Sherman says. "As a colleague once said, the greatest risk factor for tuberculosis is breathing."

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