Thus, the consistently failed disease transmissions by Aβ-, tau- and α-synuclein inocula observed so far may suggest an alternative conclusion: That Aβ-, tau- and α-synuclein aggregates, also when being seeding-active and partly able to produce neurotoxic effects, cannot transmit neurodegenerative diseases such as AD or PD. Here, MAPT is linked to Parkinson disease.