It has become evident that the prion protein (PrP) can form a diverse range of self-replicating
structures in addition to bona fide PrP Sc or strain-specific PrP Sc variants. Some self-
replicating states can be only produced in vitro, whereas others can be formed in vivo and in
vitro. While transmissible, not all states that replicate in vivo are truly pathogenic. Some of
them can replicate silently without causing symptoms or clinical diseases. In the current
article we discuss the data on PK-digestion patterns of different self-replicating PrP states in …