Fighting a lethal microbe

Scientists at Yale have discerned how the immune system fights the bacterium that causes Legionnaire’s disease.

The bacterium, Legionella pneumophila, hides from immune defenses by living and multiplying in sealed vacuoles inside cells. Craig R. Roy, Ph.D., associate professor of microbial pathogenesis and senior author of a study published in Nature Immunology in March, and colleagues found that a protein called Birc 1e is key to detecting Legionella infection.

Postdoc Dario S. Zamboni, Ph.D., lead author of the study, showed that when bacterial products leave the infected cells, Birc 1e activates a signaling pathway that stimulates a protease called caspase-1. The protease degrades other proteins in the infected cell, starting a cascade of events that results in cell death.

“Identification of Birc 1e and the caspase cascade gives us information about the process of how the body fights off infection by a potentially lethal microbe, as well as possible targets for treatments,” said Roy.