So that's where tuberculosis hides

31 January 2013
Posted by Chris Smith.

In a move that will make tuberculosis (TB) easier to treat, scientists have discovered a hidden hang-out used by the bacterium to evade immune capture or destruction by Mycobacterium Tuberculosisantibiotics.

Writing in Science Translational Medicine, Antonia Campos-Neto, from the Forsyth Institute in Massachusetts, and his colleagues have flushed out a previously unknown hiding place where TB can lurk beyond the reach of drugs or the immune system.

Using experimental mice, the team have discovered that TB bacteria (Mycobacterium tuberculosis) can get inside the stem cells that make up the bone marrow and lurk, in an inactive state, invisible to the immune system.

Bone marrow stem cells are an ideal target because they divide, rather than die, so the TB bacteria always have a home, the cells reside in a so-called immune privileged site, where the immune system is held in check, and these cells produce a molecule called an ABCG2 efflux pump, which rapidly removes anti-TB drugs from the cells.

In tests, the team were able to show that TB could be successfully cultured many months later after mice were infected via the airborne route with TB.

Even more convincing was the finding that the bug could also be grown from bone marrow samples obtained from previously-treated human TB cases, who were otherwise regarded as cured.

The good news is that the infected stem cells that the team have identified carry a specific marker on their surfaces called CD271. So now a targeted therapy can be developed to ensure the bacteria are flushed out from these cells too.

This cannot come a moment too soon: official figures show that over 2 billion people worldwide are currently TB infected...

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