Neurologic Alterations Due to Respiratory Virus Infections

Bohmwald, Karen; Gálvez, Nicolás M. S.; Ríos, Mariana; Kalergis, Alexis M.

After primary infection, most neurotropic viruses can enter the bloodstream to reach CNS, a process which is called viremia (Gonzalez-Scarano and Tyler, 1987) . Once inside the bloodstream, viruses can pass through the BBB by a transendothelial mechanism, which is transcytosis across BMECs and pericytes by endocytic vesicles (Suen et al., 2014) . Another transcellular entry method is the infection of endothelial cells, allowing the direct pass across BBB (Koyuncu et al., 2013; Suen et al., 2014) . Besides, disruption Low levels of TNF-α in CSF. Elevated IL-6 and BDNF in CSF correlates with brain damage. Cappel et al. (1975) ; Hirayama et al. (1999) ; Ng et al. (2001) ; Zlateva and Van Ranst (2004) ; Otake et al. (2007) ; Kawashima et al. (2009 Kawashima et al. ( , 2012 and Morichi et al. (2017) of BBB permeability by destabilization of TJs allow viral entry into the brain in a paracellular transmigration way (Li et al., 2015; Swanson and McGavern, 2015b) . This event is a consequence of a systemic infection that releases inflammatory mediators-such as cytokines and chemokines-besides the matrix metalloproteinase (MMP; Roe et al., 2012) . Finally, the ''Trojan Horse'' mechanism consists in the infection of bloodstream leucocytes-mainly monocytes/macrophages-which can transmigrate via paracellular route, across the permeable BBB into the CNS (Suen et al., 2014) .