In 2004, Fevrier and colleagues demonstrated that naturally occurring cellular prion proteins (PrPc) and PrPscs are released by cells in association with exosomes [130]; subsequently, exosomes from prion-infected neuronal cells have been demonstrated as being efficient initiators of prion propagation in uninfected recipient cells and, more importantly, producing prion disease when inoculated into mice [131]. Here, PRNP is linked to prion disease.