Discovery of gene that controls the speed at which patients develop tuberculosis

Scientists at the Research Institute of the McGill University Health Centre (RI MUHC) have discovered a gene that controls the speed at which patients develop tuberculosis--the first time such a gene has been discovered for this disease.

The new study published in the Proceedings of the National Academy of Science (PNAS) this week provides a new view of the mechanisms underlying the development of tuberculosis and may contribute to public health efforts aimed at containing the disease.

"About one-third of the world's population is infected by Mycobacterium tuberculosis--the bacteria responsible for tuberculosis," says Dr. Erwin Schurr, a molecular geneticist at the Centre for the Study of Host Resistance at the MUHC, and the study's principal investigator. "Of the estimated two billion people infected, only 5%-10% actually develop tuberculosis disease in their lifetime--the other 90%-95% appear to be able to contain the infection in a dormant state, so that they do not become ill." Dr. Schurr has spent the past 5 years researching why and how this happens.

The new research focused on NRAMP1--a gene already known to be involved in many other illnesses, including diseases as diverse as leprosy and rheumatoid arthritis. "We discovered that variants (alleles) of the NRAMP1 gene control the speed at which tuberculosis develops, rather than whether or not it will develop at all," says Dr. Schurr. "This is the first time a gene has been shown to control the time frame between initial infection and the disease." Certain factors are already known to increase the speed at which people develop tuberculosis. "HIV and tuberculosis are synergistic partners in crime for example," says Dr. Schurr. "They appear to accelerate disease progression when they occur together."

"Understanding the basic pathways of pathogenesis offers new targets and policies for disease prevention," notes Dr. Emil Skamene, Scientific Director of the Research Institute of the MUHC. "Academic hospitals such as the MUHC combine scientific research, technology and clinic expertise, enabling scientific breakthroughs to be developed into treatments and cures that directly benefit patients."