Chlamydia pneumoniae induces Alzheimer-like amyloid plaques in brains of BALB/c mice

Amyloid deposits resembling plaques found in Alzheimer's disease (AD) brains were formed in the brains of non-transgenic BALB/c mice following intranasal infection with Chlamydia pneumoniae. The mice were infected at 3 months of age with C pneumoniae isolated from an AD brain. Infection was confirmed by light and electron microscopy in olfactory tissues of the mice. C pneumoniae was still evident in these tissues 3 months after the initial infection indicating that a persistent infection had been established. Amyloid beta (Abeta) 1-42 immunoreactive deposits were identified in the brains of infected BALB/c mice up to 3 months post-infection with the density, size, and number of deposits increasing as the infection progressed. A subset of deposits exhibited thioflavin-s labeling. Intracellular Abeta1-42 labeling was observed in neuronal cells. Experimental induction of amyloid deposition in brains of non-transgenic BALB/c mice following infection with C pneumoniae may be a useful model for furthering our understanding of mechanisms, linked to infection, involved in the initiation of the pathogenesis of sporadic AD. (C) 2003 Elsevier Inc. All rights reserved.