The blood-brain barrier, protection of the last sanctuary, strength and fragility in the presence of bacterial and viral pathogens

The fifth lecture was entitled "The blood-brain barrier: protection of the last sanctuary, strength and fragility in the presence of bacterial and viral pathogens". Like the placental barrier, the blood-brain barrier is a monolayer of endothelial cells, and even epithelial cells in the choroid plexuses. As a result, it can be considered potentially extremely fragile in view of its responsibility as guardian of the integrity of the central nervous system, and relatively easy for a pathogen to subvert. But this is not the case. Cerebral vascularization is characterized by the maintenance of a very strict impermeability of the endothelial monolayer and a very tight control of the passage of molecules. This lecture has nevertheless shown how the major bacterial and viral pathogens responsible for meningitis and meningoencephalitis pass through the blood-brain barrier. A number of unknowns remain, however, and these have been highlighted. Understanding these mechanisms is essential to improving therapeutic and preventive approaches. What's more, understanding the mechanisms of subversion by pathogens enables us to better understand certain aspects of the physiology of molecule passage through the sanctuary represented by the central nervous system.