PRNP and variant Creutzfeldt-Jakob disease: Experimental mouse transmission studies have since demonstrated that vCJD is associated with a single strain of agent, and that the strain properties of vCJD are preserved following secondary vCJD transmission via blood transfusion [17, 18], and in PRNP codon 129 heterozygous (methionine/valine (MV) individuals [18–20].