According to the infectious or pathogens hypothesis of sporadic AD, normal ageing is associated with a weakening of the brain–blood barrier (BBB) and immune system and infection with pathogenic viruses, bacteria, fungi, or parasites leads to chronic neuroinflammation which in turn promote the production and aggregation of Aβ and P-tau and consequently neuronal degeneration [48]. Here, MAPT is linked to Alzheimer disease.