Several other in vitro assays have also been developed to bridge the gap between Western blot analysis of protease-resistant (i.e., misfolded) PrP and in vivo animal bioassay; these include protein misfolding cyclic amplification (PMCA) [15], real time quaking-induced conversion (RT-QuIC) [16] and standard scrapie cell assay (SSCA). Here, PRNP is linked to scrapie.