Nearly a century old, the BCG vaccine against tuberculosis is sparking new hope in the fight against COVID-19. Researchers are testing its potential through clinical trials, but how might it help treat patients?
With about 27,000 deaths, France was among the hardest-hit countries during the early COVID-19 pandemic. Amid ongoing treatment research, the BCG (Bacillus Calmette-Guérin) vaccine—discovered in 1921—has emerged as a candidate. A study published in Cell Stem Cell on May 7, 2020, led by Michael Sieweke at the Marseille-Luminy Immunology Center (CIML), suggests BCG could play a role against COVID-19.
BCG helps regulate inflammatory responses and activates hematopoietic stem cells (HSCs), which produce immune cells and other blood components. These HSCs, found in bone marrow, play a key role during infections and appear primed to respond even faster to subsequent threats.
Traditionally, HSCs were thought unresponsive to external stimuli like infections. Yet, this research reveals they ramp up immune cell production upon infection—and even more efficiently during repeat exposures.
HSCs not only bolster immunity but also retain "memory" of prior infections through epigenetic modifications and DNA markers. Notably, they show a moderated response to inflammatory signals.
This is crucial for COVID-19, where the immune system must combat the virus while avoiding excessive inflammation, which can lead to severe complications like cytokine storms.
These HSC insights could pave the way for treatments targeting COVID-19 and beyond. Currently, trials are underway to assess whether BCG vaccination can effectively stimulate HSCs without triggering harmful inflammation.
