Tuberculous meningitis alters the proteomic landscape of brain-derived extracellular vesicles

Tuberculous meningitis (TB meningitis), the deadliest form of <i>Mycobacterium tuberculosis</i> infection, leads to mortality and severe neurological disability despite standard therapy. Brain injury and microglial activation are major determinants of outcome, yet the mechanisms linking infection, inflammation and neuronal injury remain poorly understood. Extracellular vesicles (EVs), key mediators of cell-to-cell communication, have been investigated in pulmonary TB but their role in TB meningitis remains unexplored. We used our young rabbit model of TB meningitis to isolate pure, intact EVs from brain tissue (i.e., brain-derived EVs) from infected and uninfected rabbits and used nanoflow cytometry, transmission electron microscopy and protein quantification to characterize the EVs. Comparative proteomic profiling was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), followed by <i>in silico</i> pathway, cell-type and protein-protein interaction analyses using DAVID, Enrichr, and STRING databases. We found that EV isolation from fresh and frozen tissue was equivalent and demonstrated that <i>M. tuberculosis</i> infection activated EV biogenesis. Despite preserved vesicle morphology, EVs from infected brain showed a significant proteomic shift characterized by enrichment of TB host defense, microglial and immune activation, metabolic excitotoxicity, and neuronal injury. These proteome dysregulations suggest that infection reprograms brain EV cargo toward proinflammatory and metabolic stress responses while depleting neuronal and mitochondrial components. Collectively, these data demonstrate that <i>M. tuberculosis</i> infection alters the cargo and abundance of brain-derived EV, highlighting their potential as biomarkers and mediators of host-pathogen interactions in TB meningitis.