PRNP and variant Creutzfeldt-Jakob disease: In humans, the methionine vs. valine polymorphism at PrP residue 129 appears to influence the clinical phenotype of familial prion disease associated with the D178N PrP mutation [14], [15], as well as susceptibility to sCJD, vCJD and kuru [16], [17], [18], [19], [20].