BACE2 and Alzheimer disease: One-time-only depletion of iAβ implemented prior to the T1 crossing by AβPP-derived iAβ (at this stage, neither is the ISR elicited nor the AβPP-independent iAβ generation pathway activated) via the activation of BACE1 and/or BACE2 could be sufficient to prevent the occurrence of conventional AD and of AACD for the remaining lifetime of the treated individual;