PRNP and prion disease: In this transmission study, extended incubation periods were observed in HuMV mice compared to the HuMM mice, and, while clinical disease was not observed in the HuVV mice, the appearance of neuropathology consistent with a prion disease at autopsy indicated that PRNP codon 129 VV individuals may also be susceptible to vCJD but after very long incubation times.