In several recent studies transmissible
prion disease was induced in animals by inoculation with recombinant
prion protein amyloid fibrils produced in vitro. Serial transmission of
amyloid fibrils gave rise to a new class of
prion strains of synthetic origin. Gradual transformation of disease phenotypes and PrP(Sc) properties was observed during serial transmission of synthetic
prions, a process that resembled the phenomenon of
prion strain adaptation. The current article discusses the remarkable parallels between phenomena of
prion strain adaptation that accompanies cross-species transmission and the evolution of synthetic
prions occurring within the same host. Two alternative mechanisms underlying
prion strain adaptation and synthetic strain evolution are discussed. The current article highlights the complexity of the
prion transmission barrier and strain adaptation and proposes that the phenomenon of
prion adaptation is more common than previously thought.