APP and Alzheimer disease: Antibiotic therapy for AD patients has gained interest.37 In several studies, germ-free APP-transgenic mice show better cognitive function and lower cerebral Aβ levels than specific pathogen-free (SPF) AD mice.18,81 Our study supports antibiotic therapy, as gut bacterial depletion reduced Aβ burden in AD mice and, in particular, increased Aβ efflux-associated Abcb1 and Lrp1 across the BBB.