In vitro selection of RNA aptamers against cellular and abnormal isoform of mouse prion protein.

Prion disease is caused by conformational change of normal cellular type of prion protein (PrP(c)) folding into abnormal type (PrP(sc)). We succeeded to isolate anti-PrP(c) aptamers. In the presence of competitor RNA, anti-PrP(c) aptamers showed high affinity to PrP(c) (Kd = 10 nM). Heparin has prion binding affinity and partially interfered binding of the aptamer to PrP(c). 2'-Fluoro pyrimidine nucleotide modification still restored their binding affinity (Kd = 20 nM), which was applied for conventional dot- and western-blot assay like as antibody. We also succeeded to isolate anti-PrP(sc) aptamers appearing higher affinity to PrP(sc) in a dose-dependent manner. There is no sequence homology between those anti-PrP(c) and anti-PrP(sc) aptamers.