Using PMCA as an in vitro model for prion replication, ovine PrP was shown to inhibit the replication of VRQ/ARQ scrapie prion in VRQ/VRQ substrate with rVRQ, rARQ and rARR producing mean IC50 values of 122, 288 and 505, respectively (calculated from dot blot analysis of PMCA products). Here, PRNP is linked to scrapie.