Similar to our prior study of prion levels in long-lived AD donors (26), we performed a battery of immunochemical assays for APP, Aβ, and tau proteins in the soluble and insoluble brain fractions but did not observe any obvious trends with donor age at death or correlation to abundance of prion infectivity (SI Appendix, Figs. S5 and S6). Here, APP is linked to Alzheimer disease.