Vimentin-NF-κB signaling contributing to IbeA-mediated adhesion, invasion, and biofilm formation during Escherichia coli K1 traversal of the blood-brain barrier.

INTRODUCTION

IbeA is a critical virulence factor that is present in the GimA island in Escherichia coli (E. coli) K1, the most common cause of Gram-negative bacterial meningitis in newborns. IbeA has multiple virulence functions, including adhesion, invasion, and biofilm formation in the pathogenesis of E. coli K1 meningitis. However, it is unclear how IbeA coordinates its role in bacterial adhesion, invasion, and biofilm formation during crossing the blood-brain barrier (BBB).

METHODS

An isogenic ibeA deletion mutant (ZD1) was generated from the neonatal meningitis-associated E. coli K1 strain E44. To define IbeA-mediated virulence, bacterial adhesion, invasion, and biofilm formation were quantified in human brain microvascular endothelial cells (HBMECs) using TEER, confocal imaging, and crystal violet assays. A neonatal rat meningitis model evaluated bacterial dissemination, BBB disruption, neuroinflammation, and neurological deficits. Mechanistic studies focused on Vimentin (VIM) dynamics using lipid-raft fractionation, cytoskeleton extraction, immunofluorescence, vimentin-knockout (Vim-KO) HBMEC and Co-immunoprecipitation to assess its redistribution, post-translational modifications, and interaction with NF-κB. The functional involvement of the IbeA-VIM-NF-κB signaling pathway was further examined by modulating VIM activity with glatiramer acetate (GA) in both in vitro and in vivo experiments.

RESULTS

Deletion of ibeA and VIM significantly impaired bacterial adhesion, invasion, and biofilm formation both on HBMECs and on abiotic surfaces. In neonatal rats, infection with ZD1 resulted in higher survival rates, milder neurological symptoms, and a marked reduction of biofilm structures within the cerebral microvasculature compared with infection by the wild-type strain. IbeA-triggered post-translational modifications and cytoplasmic mobilization of VIM drive its nuclear translocation, which in turn activates NF-κB signaling. Pharmacological inhibition of VIM with GA disrupted IbeA-mediated virulence, lowering bacterial loads in the blood and alleviating neurological injury.

CONCLUSIONS

IbeA is a key virulence factor that coordinates E. coli K1 adhesion, invasion, and biofilm formation by activating the VIM-NF-κB signaling pathway. Our study establishes for the first time a direct mechanistic link between IbeA's multiple virulence functions through the above signaling pathway leading to acute BBB disruption and meningitis and identify GA as a potential drug development candidate for this disease.