APP and viral infectious disease: Infection from a variety of pathogens, including Chlamydia pneumoniae [4, 23], Herpes simplex virus [9], pseudorabies virus [39], Toxoplasma gondii [41] and Porphyromonas gingivalis [17], leads to increased Aβ production in the brain, suggesting that bacterial and viral infections in human and animal models can shift the processing of amyloid precursor protein (APP) toward the amyloidogenic pathway, resulting in increased rates of Aβ production and deposition.