Single-cell profiling of blood and cerebrospinal fluid in tuberculous meningitis

Tuberculous meningitis (TBM) is the most severe form of tuberculosis, with a fatality rate of 20-50% in treated individuals. Although corticosteroid therapy can increase survival in HIV-negative people with TBM, better antimicrobial and host-directed therapies are required to improve outcome. There is, therefore, a need to better understand local immunopathologic pathways. Despite its power in identifying disease-specific cellular profiles, single-cell RNA-sequencing (scRNA-seq) has been underutilized in cerebral samples in brain infection. We employed scRNA-seq to analyze fresh pretreatment cerebrospinal fluid (CSF) from four TBM patients, along with paired peripheral blood mononuclear cells (PBMCs). While 29 cell subtypes were present in both tissues, their relative abundance varied significantly. In particular, CSF was enriched with highly inflammatory microglia-like macrophages, GZMK -expressing CD8 ⁺ T cells, and CD56 ^bright NK cells. The latter two subsets exhibited features associated with dysfunctional cytotoxicity. Across multiple cell types, inflammatory signaling pathways were increased and oxidative phosphorylation was decreased in CSF compared to PBMCs. This study highlights the value of scRNA-seq for exploring CSF immunopathogenesis in TBM patients and offers a resource for future studies investigating the pathophysiology of TBM and other brain infections, including potentially targetable cell populations linked with immune-mediated pathology.