The immune response to the bacterium that causes tuberculosis
(TB) varies between patients of different ethnic origins, according
to new research from the MRC's National Institute of Medical
Research (NIMR; now part of the Francis Crick
Institute) and Queen Mary, University of London.
The findings raise important implications for the development of
tests to diagnose and monitor treatment for the disease.
TB is an infection caused by the bacterium Mycobacterium
tuberculosis. It commonly affects the lungs. While the number of
cases reduced in the UK due to BCG (TB) vaccination, improvements
in living standards and the introduction of effective antibiotic
treatment, it has been on the increase since the late 1980s. TB
also remains a major global health problem, with nearly 9 million
new cases and 1.4 million deaths in 2011.
Led by Adrian Martineau at NIMR and Queen Mary University of
London, the researchers analysed the immune response of 128
newly-diagnosed TB patients in London who were divided by ethnicity
into those of African (45), European (27), Asian (55) or mixed
European/Asian (1) ancestry.
By analysing the levels of various inflammatory markers in blood
samples taken before treatment, the scientists showed that immune
responses of Asians and Europeans were similar to each other, but
different from those of Africans. This difference was caused by
ethnic variation in the patients' genetic make-up: it was not
related to the strain of TB bacterium that the patients were
infected with.
Dr Martineau said: "The TB bacterium has co-evolved with humans
following migration to Europe and Asia some 70,000 years ago, and
different strains of the TB bacterium disproportionately infect
particular ethnic groups. Our study has shown, for the first time,
that it is ethnic differences in the patient's genetic make-up that
cause most of the variation in immune responses - with little
effect of the TB strain they are infected with."
Dr Anna Coussens, who measured immune responses in patient
samples at the NIMR, added: "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."
The paper, Ethnic
variation in inflammatory profile in tuberculosis, is published
in PLOS Pathogens.