PRNP and prion disease: We and others have shown that mice devoid of PrPC (Prnp0/0) were resistant to prion infection, neither propagating PrPSc or prions in their brains nor developing disease even after intracerebral inoculation with prions [3,4,5,6], reinforcing that the conversion of PrPC into PrPSc leading to the accumulation of PrPSc in the brain is a key pathogenic event in prion diseases.