PRNP and variant Creutzfeldt-Jakob disease: The vCJD prions transmit disease to wild-type mice far more efficiently than any other form of human prion disease [26,27,49,122] and in transgenic mice faithful propagation of the vCJD phenotype is dependent upon homozygous expression of human PrP 129 methionine [28,49,63,170,171] (Figure 2).