"However our study has shown, for the first time, that it is actually ethnic differences in the patient's genetic make-up that cause most of this variation in immune responses with little effect of the TB strain they are infected with."
By analysing blood samples taken from 85 of the original cohort after an eight-week period of intensive treatment, the researchers found that ethnic variation in immune responses became even more marked. A number of immunological biomarkers, which correlated with either fast or slow clearance of the TB bacteria, were identified and found to differ between Africans and Europeans/Asians.
Dr Anna Coussens, who measured immune responses in patient samples at NIMR, said: "These findings have important implications, both for the development of new diagnostic tests, which increasingly rely on analysing the immune response, and also for work to identify candidate biomarkers to measure response to anti-TB treatment. In the future, diagnostic tests and biomarkers will need to be validated in different ethnic populations."
A key factor in determining the ethnic variation identified in the study appears to be the patients' genetic type of vitamin D binding protein a molecule which binds vitamin D in the circulation.
Dr Martineau said: "There are different genetic types of this protein which vary in frequency between ethnic groups, adding to the growing evidence that vitamin D and the way it is carried in the blood is crucial in determining how a patient's immune system will respond to TB."
Further studies in other populations are now needed to validate the ethnic difference identified.
This work was funded by the British Lung Foundation and the Medical Research Council (MRC).
Dr John Moore-Gillon, Honorary Med
|Contact: Katrina Coutts|
Queen Mary, University of London