Aisling Irwin reports on the Tuberculosis 2000 conference at the Royal Society of Medicine. Scientists hope that they may have found a new treatment for tuberculosis based not on drugs but on immunotherapy.
Trials of immunotherapy are under way across the world, with the most advanced trial, a phase three clinical trial, being done in South Africa. John Grange, head of microbiology at the National Heart and Lung Institute, told the conference: "In a year's time we will know once and for all whether immunotherapy will be a powerful new tool in TB."
Although TB is one of the most prevalent chronic infectious diseases worldwide, most of us have immune systems that deal very well with it. Only one in ten people who are infected by the tubercle bacillus go on to develop the disease.
The reason is that the bacillus causes two immune responses in humans, depending on the balance that person has between two types of cells. One response leads to protection against the disease by stimulating Th1 helper T cells. "The other causes the immune system to break down the person's own tissue," said Dr Grange. Most people get the protective response.
The first step in developing the immunotherapy came in the 1970s, in Africa, when Dr Grange and his colleague John Stanford discovered a harmless relative of the tubercle bacillus, mycobacterium vacii. When this bacillus enters humans, it can only stimulate the beneficial response.
The idea is to give TB sufferers mycobacterium vacii, which will tell the immune system that it got its response to the first bacillus wrong.