Intracerebral injection of brain extracts from Alzheimer's disease (AD) patients into appropriate mouse models was previously found to drastically accelerate the deposition of A beta amyloid in the recipient animals indicating a prion-like activity. In this study we show that this prion-like activity can be also identified by using a cell culture model of A beta plaque formation. Analysis of biochemical fractions of AD brain extract indicate that the seeding-activity correlated with the presence of A beta peptide and A beta derived aggregates. In vitro-formed fibrils were also active but their activity was low and depending on the fibril structure and conditions of fibril formation. Our data indicate a conformational basis of the observed seeding effect and suggest the utility of our cell model for further studies on the prion-like activity of AD extracts. (C) 2018 Elsevier Inc. All rights reserved.