Persistence of Aβ seeds in APP null mouse brain.

Cerebral β-amyloidosis is induced by inoculation of Aβ seeds into APP transgenic mice, but not into App(-/-) (APP null) mice. We found that brain extracts from APP null mice that had been inoculated with Aβ seeds up to 6 months previously still induced β-amyloidosis in APP transgenic hosts following secondary transmission. Thus, Aβ seeds can persist in the brain for months, and they regain propagative and pathogenic activity in the presence of host Aβ.