Boston Globe (01.31.13)
A Forsyth Institute research team found latent TB bacteria concealed in “bone and cartilage-forming stem cells in bone marrow” where the bacteria can evade immune system activity and antibiotics that would normally kill them. This ability to hide from treatment by lying dormant in bone marrow stem cells could explain how TB is able to persist for years and recur, according to the Forsyth team, which is composed of stem cell specialists and infectious disease researchers from Stanford University School of Medicine, Cambridge University, and India.
The study first demonstrated that it was possible to infect bone marrow stem cells with TB in the laboratory. The researchers then infected mice with TB bacteria engineered to stay dormant until activated by a drug. When they tested the mice, the team found dormant TB bacteria in both the lungs and bone marrow stem cells. The team was also able to grow TB bacteria from bone marrow stem cells harvested from nine people—thought to be long cured of TB—in a remote village in India.
The Forsyth study does not provide definitive proof that the bone marrow stem cells are the TB bacteria’s hiding place. Other theories suggest TB bacteria can persist in a “zombie-like” state that enables the bacteria to resist treatment and then reactivate later. However, the study does contribute to researchers’ understanding of TB’s latent phase and could point to how new treatments might target TB bacteria hiding in the safe harbor of the bone marrow stem cells. Latent infections comprise 90 percent of the world’s 2.2 billion TB cases.
The full report, “CD271+ Bone Marrow Mesenchymal Stem Cells May Provide a Niche for Dormant Mycobacterium Tuberculosis,” was published online in the journal Science Translational Medicine: Integrating Medicine and Science (2013; doi: 10.1126/scitranslmed.3004912).