APP and Alzheimer disease: Infection of certain bacteria including Helicobacter pylori, Porphyromonas gingivalis, Chlamydia pneumonia, and Borrelia burgdorferi, has been found to be risk factors for the development of dementia (20–22, 118, 119) In an AD mouse model (APP/PS1 mice), Bordetella pertussis respiratory challenge led to T cell infiltration into the brain and increased microglial activation and Aβ deposition (120).