The VgrG2 effector of Acinetobacter baumannii mediates immune evasion by repressing Csu pilus assembly and triggering phagocyte methuosis [scRNA-seq]

This study identifies the type VI secretion system (T6SS) effector VgrG2 as a critical virulence regulator in A. baumannii. VgrG2 employs a two-pronged strategy to undermine host innate immunity.

First, it transcriptionally represses the major adhesin Csu pilus, reducing bacterial recognition, phagocytic uptake, and neutrophils recruitment. Second, VgrG2 directly targets and hyperactivates the small GTPase Rac1 within phagocytes. This leads to actin cytoskeletal disarray, which drives excessive macropinocytosis, resulting in compromised phagocytosis and methuosis—a non apoptotic, vacuole dependent death specific to phagocytes.