IMPY, a potential β-amyloid imaging probe for detection of prion deposits in scrapie-infected mice

IntroductionA potential single-photon emission computed tomography imaging agent for labeling of Aβ plaques of Alzheimer's disease, IMPY (2-(4′-dimethylaminophenyl)-6-iodo-imidazo[1,2-a]pyridine), would be effective in detection of prion amyloid deposits in transmissible spongiform encephalopathies (TSEs).MethodsIn vitro autoradiographic studies were carried out with [125I]IMPY on brain sections from scrapie-infected mice and age-matched controls. Competition study was performed to evaluate the prion deposit binding specificity with nonradioactive IMPY.ResultsBinding of [125I]IMPY was observed in infected brain sections, while on age-matched control brain sections, there was no or very low labeling. Prion deposit binding was confirmed by histoblots with prion protein-specific monoclonal antibody 2D6. In the presence of nonradioactive IMPY, the binding of [125I]IMPY was significantly inhibited in all regions studied.ConclusionsThese findings indicate that IMPY can detect the prion deposits in vitro in scrapie-infected mice. Labeled with 123I, this ligand may be useful to quantitate prion deposit burdens in TSEs by in vivo imaging.