The Strain Properties of Korean and North American Chronic Wasting Disease Prions Are Indistinguishable.

Abstract

BACKGROUND: Chronic wasting disease (CWD) in North America is an ineradicable and deadly infectious neurodegenerative disorder of free-ranging and captive cervids caused by prions. While CWD was inadvertently introduced to South Korea (SK) following importation of subclinically diseased elk from North America, it is unclear whether this event represented a bottleneck infection by an uncommon prion strain and/or if variant strains evolved during subsequent transmissions to additional farmed cervid species residing in SK. Considerable uncertainty therefore surrounds the prevalence and properties of SK CWD prion strains. METHODS: We propagated prions from the brains of 9 diseased SK cervids to multiple lines of genetically modified, CWD-susceptible mice. We ascertained the strain properties of SK CWD prions by evaluating disease outcomes and by characterizing the infectious and biochemical properties of the resulting prions. RESULTS: Multiple SK CWD prion isolates produced uniform disease outcomes during iterative transmissions in both gene-targeted and transgenic mice. SK CWD prions had infectious and biochemical properties, including conformational features, that were indistinguishable from those of North American CWD prions. CONCLUSIONS: These invariant features are consistent with infection of SK and North American cervids by the same CWD prion strain. Our findings contribute to a developing picture where a single, dominant prion strain is responsible for contagious CWD transmission among North American and SK cervids. The stability and consistency of this established strain contrasts with the highly diverse and relatively unstable features of incipient prion strains causing novel emergent CWD infections in moose, reindeer, and red deer from Northern Europe.