The slow-growing Mycobacterium tuberculosis cause TB. However, when they invade a body, the host cells summon up additional immune cells to kill or limit the damage the bacterium could cause. Just how host cells trigger that response has remained unknown. However, according to research, published in Science (October), a receptor – named CCR5 - on the host cells is responsible.
The researchers, working at Imperial College London; Cambridge and Oxford Universities; the National University of Singapore; Nanyang Technological University, Singapore; University of Basel, Switzerland, and Lionex Diagnostics and Therapeutics GmbH, Germany, have demonstrated that, without the receptor - named CCR5 - mycobacteria thrived within the host cells.
‘These results describe a novel mechanism whereby Mycobacterium tuberculosis communicates with the human immune system,’ explained Dr Beate Kampmann, of the Wellcome Trust Centre for Clinical Tropical Medicine and the Department of Paediatrics, Imperial College London, and one of the study’s authors. ‘Another piece of this complex jigsaw has been filled in, which will help us to target TB with very specific drugs or vaccines. We can now test potential vaccines or drug candidates for the desired effect, because we understand better how they should act.’
Because TB is a big problem for HIV patients, because their weakened immune system renders them highly susceptible to this disease, the researchers believe their study will interest scientists working on the development of new drugs to combat HIV, which work by inhibiting the CCR5 receptor that plays an important role in HIV-infection. The new research suggests that such drugs could impair the ability to fight off TB in HIV-infected patients receiving CCR5 receptor antagonists.
Research funding: The Wellcome Trust, London; UK Medical Research Council (MRC) and the Swiss National Science Foundation.
Source: Imperial College London
Mechanism of virulent TB strain discovered
Researchers have identified a mechanism that contributes to the virulence of a particular strain of TB, which possibly makes it more contagious than other strains.
Most people infected with Mycobacterium tuberculosis do not show symptoms, and perhaps a third of a population might carry the bacteria. However, less than one in ten will develop TB. However, about 25% of those infected with the CH strain do contract TB.
Dr Robert Wilkinson and researchers at the Wellcome Trust Centre for Clinical Tropical Medicine, Imperial College London, and Professor Mike Barer at Leicester University, have identified a segment of the CH genome which, if absent, modifies the immune system’s response to the strain and makes it more likely to result in TB.
Source: Proceedings of the National Academy of Sciences of the USA