TB research is getting a scientific boost as well a financial one. The field moved to the cutting edge of medical research two years ago after scientists funded by the Wellcome Trust sequenced the M. tuberculosis genome. Researchers suddenly had 4,000 genes to screen, raising the possibility of targeted therapies that could be far more effective than general antibiotics. The bacteria usually becomes active after the patient's immune system weakens for some other reason, such as infection by the HIV virus. In fact, TB is the leading cause of death for AIDS victims.
Researchers still have only a dim idea of what prompts the bacterium to turn deadly.
It lurks in immune system cells located in the lungs called macrophages, which ingest foreign microorganisms. M. tuberculosis can apparently survive inside the macrophages, where it grows and divides into protective structures called granulomas. The bacteria lie dormant in these structures until activated, when they break out and attack the lungs. One of the most promising drug candidates so far, reported in June by PathoGenesis Corp. of Seattle, attacks the bacteria in the macrophage. Most significantly, the compound worked against the bug in its dormant phase.