Figure 1.

Pathogen Mechanisms for Crossing the Blood Brain Barrier

(A) The NVU is composed of astrocyte endfeet, pericytes, and endtothelial cells and the local production of type I IFNs has a major role in controlling opening of the BBB (Daniels et al., 2017, Lazear et al., 2015). Micro-organisms utilize three main mechanisms to directly transit the BBB.

(B) Trans-cellular route by which viruses or infected cells directly cross through EC (Dahm et al., 2016).

(C) Para-cellular route whereby the breakdown of the tight junctions allows access of infected cells or extracellular pathogens to access the peri-vascular unit (Santiago-Tirado et al., 2017, Shi et al., 2010, Vu et al., 2013).

(D) Lytic mechanisms in which the ability to infect EC and lyse these cells allows pathogens to access the brain (Konradt et al., 2016).