The pattern recognition reagents RAGE VC1 and peptide p5 share common binding sites and exhibit specific reactivity with AA amyloid in mice

Soluble RAGE VC1 and peptide p5 have similar ligand binding properties and specifically localize with visceral AA amyloid deposits in mice.

Binding of radiolabeled RAGE VC1 and p5 to synthetic amyloid fibrils was evaluated using in vitro "pulldown" assays in the presence or absence of RAGE ligands. Radioiodinated RAGE VC1 and technetium-99 m-labeled p5 were studied in mice with systemic AA amyloidosis using dual-energy SPECT/CT imaging, biodistribution and microautoradiography.

Soluble RAGE VC1 competed with radioiodinated peptide p5 for binding to rVλ6Wil, Aβ (1-40) and IAPP fibrils but not with the higher affinity peptide, p5R. Pre-incubation with AGE-BSA abrogated binding of VC1 and p5 to rVλ6Wil fibrils. Dual-energy SPECT/CT images and quantitative tissue biodistribution data showed that soluble RAGE VC1 specifically bound AA amyloid-laden organs in mice as effectively as peptide p5. Furthermore, microautoradiography confirmed that RAGE VC1 bound specifically to areas of Congo red-positive amyloid in mouse tissues but not in comparable tissues from control WT mice.