Nucleic acid-free mutation of prion strains.

While prions share the ability to propagate strain information with nucleic acid-based pathogens, it is unclear how they mutate and acquire fitness in the absence of this informational component. Because prion diseases occur as epidemics, understanding this mechanism is of paramount importance for implementing control strategies to limit their spread and for evaluating their zoonotic potential. Here we review emerging evidence indicating how prion protein primary structures, in concert with PrP(Sc) conformational compatibility, determine prion strain mutation.