Study Reveals How Bacteria Outsmart the Immune System

Hebrew University of Jerusalem scientists have identified how a common bacterial pathogen manipulates human immune defenses through a single, multifunctional protein that disrupts key signaling at two different control points. Published in Advanced Science, their study explains how enteropathogenic Escherichia coli (EPEC), which causes intestinal infections, uses one component to disable the body’s alarm system while preventing its repair, offering insights into how bacteria gain control during infection.

Led by Yaakov Socol, the research examines how EPEC deploys a specialized “injection system” to transfer bacterial proteins directly into human cells. Once inside, these molecules alter cellular machinery to create conditions favorable for the pathogen.

One such protein, known as NleD, was previously recognized for weakening host defenses by cleaving signaling molecules that coordinate immune communication. Normally, these messengers allow cells to detect infection and initiate protective responses. When NleD degrades them, the cell’s capacity to sound the alarm is reduced.

The new findings reveal that NleD takes this interference further. Beyond cutting the initial signaling molecules, the protein also binds to another immune regulator responsible for modulating those same signals. Rather than destroying it, NleD blocks its activity, preventing the regulator from reconnecting the disrupted network. This dual action allows the bacterium to silence the immune response and stop the cell from re‑establishing control afterward.

By acting on both the primary alert mechanism and its failsafe, the bacteria gain a strong foothold in the host environment. The discovery highlights how a single bacterial factor can coordinate multiple strategies to suppress defenses, an efficiency that may help explain why certain infections persist or spread.

Understanding such finely tuned interactions provides a clearer view of how bacteria exploit host systems. Instead of overpowering the immune response, they subtly hijack it, reshaping normal regulatory processes to their own advantage.

As antibiotic resistance grows, this knowledge supports new approaches that target specific bacterial‑host interactions rather than the bacteria as a whole. Findings like these may eventually inform treatments designed to neutralize the manipulative tactics pathogens use to evade detection and maintain infection.