BCG-Infected Dendritic Cells Induce TNF-alpha Dependent Cell Cluster Formation That Damage theBlood Brain Barrier

Abstract

Abstract Central nervous system tuberculosis (CNSTB) is the most serious manifestation of extrapulmonary tuberculosis infections representing 5–10% of all cases. How Mycobacterium tuberculosis (Mtb) crosses the blood-brain barrier (BBB) and enters the CNS is not well understood. We applied a novel in vitro model of BBB model that consists of primary brain astrocytes and microvessel endothelial cells to test the mechanisms how mycobacterium-infected DCs interact with peripheral blood mononuclear cells (PBMC) and affect the BBB. We show that mycobacterium hinders DC migration, and infected DCs adhere to brain microvessel endothelial cells and induce PBMC cell cluster formations. Infected DC-induced cell clusters contain 24% CD11c+, 57%CD11b+, and 16% CD4+ cells. PBMC and infected DC clusters strongly adhered to the in vitro BBB and over time induced cluster associated damage (CAD). CAD correlated with mitochondrial disorganization and the degradation of tight junction proteins ZO-1 and claudin-5, and upregulation of cellular adhesion molecules VCAM-1 and ICAM-1 on endothelial cells. Anti-TNF-a inhibition reduced cell cluster formation as well as ICAM-1 expression on brain microvessel endothelial cells and mitigated CAD. This research leads to better knowledge in understanding how mycobacteria infected cells affect the BBB that could lead to better therapeutic treatments for mycobacterial infection of the CNS.