I don’t believe the plaques have been shown to be prion based, but who knows what the transmission mechanism might be.

More relevantly, the etiology is still a mystery, and nobody knows if the amyloid β is a defense, cause, mechanism, or harmless side effect of Alzheimer’s. Drugs attacking plaque have not made a difference on the disease in clinical trials. In fact the plaque theory seems to have been supported by fraud (causing a president of Stanford to be ejected) and distracted research for years.

People are working on other causes, most of which lately has focused on the tau protein.