Listeria-infected macrophages promote biomechanical alterations in endothelial cell monolayers for transmigration.

Intracellular pathogens, such as Listeria monocytogenes (LM), manipulate host cells to spread from the initial infection site to distant organs through the bloodstream. For that, LM hijacks mononuclear phagocytes to traverse vascular endothelial cell (EC) linings, but how transmigration is regulated by ECs is poorly understood. Here, we show that LM infection profoundly alters EC biomechanical responses to macrophages (MΦs). Videomicroscopy revealed that EC-MΦ contact induces EC polarization, alignment, and reduced motility. However, only interactions with uninfected MΦs increased EC traction and monolayer stresses and barrier integrity. This biomechanical response is largely contact-dependent and significantly attenuated during infection, thus contributing to the enhanced rate of LM-infected MΦ transmigration. Consistently, in the zebrafish model, infection increased endothelial permeability and phagocyte extravasation. These findings reveal that LM infection overrides MΦ-induced endothelial barrier strengthening to promote pathogen dissemination, a biomechanical strategy that could be harnessed for infection control.