PRNP and scrapie: It is possible that the ovine/caprine PrP sequence is required to allow a more efficient interaction of the BSE agent with human 129M-PrP, however it is important to note that no disease transmission has been observed in HuMM mice following inoculation with several isolates of natural and atypical sheep scrapie and goat scrapie (Wilson et al., 2013, 2012), indicating that it is not simply the presence of the ovine or caprine PrP sequence that facilitates transmission to animals expressing human PrP.