Nuvolone et al., 2015 argue that the in vitro generated PrP fibrils are not infectious and may trigger neurotoxicity by different pathways from those activated in prion infections; however, the discrepancies between these different groups may also be due to strain-dependent variations in prion infection, as shown by a number of different research groups, in both murine and human prion diseases (Baker et al., 1999; Tixador et al., 2010; Ayers et al., 2011). This evidence concerns the gene PRNP and prion disease.