PrP E219K reliably amplifies prions from both humanized transgenic tg650 mouse BH and directly from patient samples, initiating amplification between 3 and 36 hours for tg650-passaged sCJD, 11 and 31 hours for tg650-passaged vCJD, 0 and 27 hours for patient-derived sCJD, 17 and 35 hours for patient-derived vCJD, over a 5- to 8-log dilution range depending on the strain. This evidence concerns the gene PRNP and variant Creutzfeldt-Jakob disease.