- Aβ vaccination has been shown to induce remarkable clearance of brain amyloid plaques in mouse models of Alzheimer's disease (AD). However, the extent to which antibody-mediated Aβ clearance is affected by predominant formation of Aβ42 over Aβ40 is unclear. Here we demonstrate for the first time that in a mouse model carrying the human APP mutations KM670/671NL and the human PS1 mutation P166L, Aβ vaccination does not result in plaque clearance. This was in spite of the strong T- and B-cell immune responses evoked under the DR1501 genetic background and the activation of microglia at sites of Aβ plaques. Our findings suggest the existence of antibody-resistant forms of Aβ deposits in the brain consisting of primarily Aβ42, and shed light on the mechanisms of antibody-dependent amyloid clearance as well as novel therapeutic strategies for AD.