TB hideout found inside stem cells

New Delhi, Jan. 31: Scientists, using bone marrow samples from members of the Idu Mishmi tribe in Arunachal Pradesh, have discovered the hideout in the human body where tuberculosis bacteria can lie dormant for years.

A collaborative study by Indian and US scientists has identified stem cells in the bone marrow that seem to serve as a "protective niche" for TB germs to evade the drugs' action and the human immune system.

The study, published yesterday in the journal Science Translational Medicine, relied on samples of bone marrow provided by volunteers among Idu Mishmi tribals who live in a remote mountain range in Arunachal's Lower Dibang Valley. By volunteering to participate in the study, scientists say, this indigenous community has contributed to efforts to resolve a long-standing medicine mystery.

While effective antibiotics have been available to treat and cure TB for more than 50 years, TB bacilli remain in the body despite a successful course of treatment and can cause the disease to recur after years or even decades.

Now Bikul Das, at the Stanford University Medical Centre, and his collaborators have found that cells called mesenchymal stem cells (MSCs) in the bone marrow appear to provide a "long-term protective" burrow for TB bacteria.

"We think we've got their hiding place," said Das, who had graduated from Guwahati Medical College. before leaving India for study and research. "We've got evidence for the presence of TB bacteria in human bone marrow MSCs."

The researchers collected bone marrow samples from nine volunteers from the Idu Mishmi tribe who had successfully been treated with anti-TB medications and had been declared cured of the disease.

They found bacterial genetic material in the MSCs from eight of the nine bone marrow samples, and were able to isolate living TB bacteria from two clusters of the MSCs from among the nine.

"They were live, viable, but non-replicating TB bacteria," said Ista Pulu, a gynaecologist who is himself a member of the Idu Mishmi community and who collaborated in the study by motivating people to participate and help collect samples of their bone marrow.

The scientists say the study could have used samples from other populations as it only required patients successfully treated for TB. But, Das said, conducting the clinical study among the Idu Mishmis provided certain advantages.

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TB hideout found inside stem cells