PRNP and Creutzfeldt Jacob disease: Homogenates from Tg(FFI-K5) and Tg(CJD-A21) mice, expressing 3F4-tagged mutant PrPs, were also inoculated in Tg(WT-E1+/+) mice overexpressing WT moPrP with the 3F4 epitope [13], and in Tg(CJD-G1+/+) mice, which express low levels of 3F4-tagged D177N/V128 PrP and do not spontaneously become ill [14].