APP and Alzheimer disease: Likewise, two previously reported single-domain camelid VHH antibody fragments, designated PrioAD12 and PrioAD13 and specifically binding to oligomeric Aβ1-40 and Aβ1-42, respectively, were shown to detect Aβ oligomers in the retina and blood of APP/PS1 mice before amyloid accumulation in the brain and before the cognitive decline, pointing to the potential of such nanobodies as early diagnostic tools for AD [48].