CCL2 and infection: The MOIs of 0.1 and 1 used to treat endothelial cells produced significant amounts of pro-inflammatory cytokines IL-6 and CCL2, so the MOI of 1 was chosen for the subsequent experiments as a way to mirror direct infection of brain endothelial cells, but not microglia and astrocytes (Figures 6C–E; Supplementary Figures 4A, B).