We alsodetected PrPSc-like PK-resistant PrP in parental N2acells, which express mouse PrPC only at endogenous levels,at 5 passages after infection with IAV/WSN, indicating that overexpression ofPrPC is not necessary for IAV/WSN infection to induceconversion of PrPC intoPrPSc-like PrP (Fig. 2b). This evidence concerns the gene PRNP and infection.