Sleeper Cells

Mycobacterium tuberculosis bacteria, shown here (coloured pink) in the lung tissue of a mouse, are responsible for the most deadly infectious disease in the world: tuberculosis, which kills around 1.25 million people annually. While the existing vaccine protects infants against a certain severe form of the disease, it offers little protection to adults against the more common form affecting the lungs. Scientists have long wondered why the vaccine-trained immune system often fails to eradicate such infections. And recent discoveries suggest an answer: the sneaky bugs essentially play dead during a strong immune response, staying dormant until the threat passes. Indeed, genetic screens revealed that genes encoding proteins involved in stress response and dormancy were important for bacterial survival in pre-vaccinated, infected mice, while those encoding virulence factors were not. It’s hoped these insights into the bacteria’s survival strategy will inform new treatments to outwit the evasive killer.

Written by Ruth Williams

Ruth Williams

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Ruth is a freelance science journalist based in the US. She's a regular correspondent for The Scientist, and her work has appeared in The Lancet, Nature, Scientific American Mind, BBC Focus and elsewhere. Twitter @rooph

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• Image from work by Kimra S. James and colleagues
• Division of Microbiology & Immunology, Department of Pathology, University of Utah, Salt Lake City, UT, USA
• Image originally published as 'with credit only' –  Creative Commons Attribution 4.0 International (CC BY 4.0)
• Research published in NPJ Vaccines, May 2025