Furthermore, these same mouse studies have confirmed that the BSE/vCJD strain is not generally altered by the tissue of origin [47,55,56], the PRNP codon 129 genotype of the individual [56,57,58], geographical location [59,60], age [60] or following secondary human transmission of vCJD through blood transfusion [56,61]. This evidence concerns the gene PRNP and variant Creutzfeldt-Jakob disease.