Bacterial meningitis in the early postnatal mouse studied at single-cell resolution

Bacterial meningitis is a major cause of morbidity and mortality, especially among infants and the elderly. Here we study mice to assess the response of each of the major meningeal cell types to early postnatal E. coli infection using single nucleus RNA sequencing (snRNAseq), immunostaining, and genetic and pharamacologic perturbations of immune cells and immune signaling. Flat mounts of the dissected arachnoid and dura were used to facilitiate high-quality confocal imaging and quantification of cell abundances and morphologies. Upon infection, the major meningeal cell types – including endothelial cells (ECs), macrophages, and fibroblasts – exhibit distinctive changes in their transcriptomes. Additionally, ECs in the arachnoid redistribute CLDN5 and PECAM1, and arachnoid capillaries exhibit foci with reduced blood-brain barrier integrity. The vascular response to infection appears to be largely driven by TLR4 signaling, as determined by the nearly identical response induced by LPS administration and by the blunted response to infection in Tlr4 -/- mice.