Mycobacterium tuberculosis

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Researchers in Vietnam have found that the severity of tuberculosis is affected by the genetic makeup of both the bacterium and the patient.

They hope that understanding the relationship between bacterial and host genetics will aid the development of more effective treatment for the disease.

The research was published last week (28 March) in PLoS Pathogens.

Scientists looked at gene variations in two sets of patients, one with uncomplicated tuberculosis of the lungs and one with tuberculosis meningitis — severe disease that occurs when the infection spreads to membranes surrounding the brain and spinal cord.

They also looked at the genetic lineage of the Mycobacterium tuberculosis bacteria infecting the patients.

They found that people with a specific genetic variation in an immune system gene called TLR2 were more likely to suffer from tuberculosis meningitis caused by a strain of M. tuberculosis called East Asian/Beijing.

But M. tuberculosis of Euro-American lineage was more likely to cause disease only in the lungs, suggesting it is less capable of causing tuberculosis meningitis in the Vietnamese population.

Awareness of the relationship between pathogen and patient genetics might explain why studies investigating the variations in human genetics as a risk factor sometimes show different results in different areas of the world, says Maxine Caws, a researcher at the Wellcome Trust Major Overseas Programme, based at the Oxford University Clinical Research Unit in Vietnam and coauthor of the study.

This susceptibility might not be due merely to ethnic genetic differences. It could also be caused by genetic differences between M. tuberculosis populations in different parts of the world, she adds.

"Ultimately, better understanding of the immune response to a pathogen can help us to design better globally effective vaccines, which historically have been the most successful way to combat infectious diseases," Caws told SciDev.Net.

She adds that, while the Beijing strain is most common in Asia, its prevalence is increasing rapidly in many parts of the world and "this is of deeper concern because this strain of tuberculosis appears to be very good at acquiring drug resistance."

Link to full paper in PLoS Pathogens