Project Summary Bacterial meningitis is a serious life-threatening infection of the central nervous system (CNS) that occurs when bacteria are able to cross highly specialized brain endothelial cells (BECs) and enter the brain. While modern medical intervention has transformed bacterial meningitis from a uniformly fatal disease, many survivors exhibit permanent neurological damage. One major complication during bacterial meningitis is stroke. The CNS is protected by the blood-brain barrier (BBB) and meningeal blood-cerebrospinal fluid barrier (mBCSFB), that are comprised of BECs and make up the blood vessels in the brain. When compared with peripheral endothelial cells, BECs exhibit unique properties that contribute to barrier function and support proper brain homeostasis. However, during bacterial meningitis, BECs fail to protect the brain. The goal of this study is to use the most state-of-the-art human stem-cell modeling techniques to assess how BECs fail to maintain their unique properties and protect the brain during bacterial meningitis. In Aim 1 we will explore how Group B Streptococcus (GBS) alters the cellular uptake pathways endocytosis and pinocytosis that is shut off in healthy BECs, and how this contributes to GBS invasion of BECs and progression to meningitis. In Aim 2, we have discovered that GBS can disrupt the efflux transporter P-glycoprotein (Pgp), we will discover the host cell signaling that contributes to Pgp disruption and identify the GBS factor responsible. Synergy between aims exists because both interrogate unique properties of BECs and how they fail during disease. Our aims will determine mechanisms of BEC failure during infection yet have implications in many neurological disorders and may uncover avenues for novel therapeutic interventions.