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Genes linked to African TB

17 August, 2010

One-third of the world's population are believed to be infected with M. Tuberculosis, the bacterium that causes TB. Each year, at least nine million people are in need of treatment for TB, and more than two million people die from the disease.

The identification of the genetic variant linked with greater TB susceptibility was recently published in the prestigious journal Nature Genetics. Using a technique known as a genome-wide association (GWA) study, the researchers scanned 333,000 genome sequence variants in more than 11,000 people living in Africa.

The study was led by Professor Adrian Hill from the University of Oxford, UK, and Professor Rolf Horstmann from the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany.

University of Otago Centre for International Health Director Professor Philip Hill oversaw the study's arm in The Gambia. This work involved providing DNA samples from TB cases and controls proven by laboratory testing to have or not have TB, respectively.

Professor Hill says genetics is known to be important in determining whether someone's exposure to M. tuberculosis will lead them to develop the disease.

"If you are closely related to a TB patient and have the same amount of exposure to M. tuberculosis as someone else with no such relatives, then over your lifetime you're more likely to develop TB disease than they are."

While this newly identified gene variant is likely to be only one of many working together to cause increased TB susceptibility, the finding provides a glimpse of where future research may lead, Professor Hill says.

"Identifying genetic variants that are linked to TB susceptibility can help with breakthroughs in understanding the relationship between humans and the disease.

"For example, if a variant of a gene that encodes for a particular component of the immune system is found to be associated with developing TB, then this part of the immune system can be investigated as a target to be stimulated by new interventions such as vaccines."

The genetic variant, called rs4331426, is the first disease-related gene marker in African populations to be identified through a GWA study.

"This achievement demonstrates that GWA studies can be successfully used to identify genetic predispositions to TB and other infectious diseases in African populations. Previously it had been thought that the high degree of genetic diversity in Africans would prevent the technique from producing meaningful results," Professor Hill says.

Source: University of Otago

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