Prion Protein of 106 Residues Creates an Artificial Transmission Barrier for Prion Replication in Transgenic Mice

A redacted prion protein (PrP) of 106 amino acids with two large deletions was expressed in transgenic (Tg) mice deficient for wild-type (wt) PrP ( Prnp 0/0) and supported prion propagation. RML prions containing full-length PrP Sc produced disease in Tg(PrP106) Prnp 0/0 mice after ∼300 days, while transmission of RML106 prions containing PrP Sc106 created disease in Tg(PrP106) Prnp 0/0 mice after only ∼66 days on repeated passage. This artificial transmission barrier for the passage of RML prions was diminished by the coexpression of wt MoPrP C in Tg(PrP106) Prnp +/0 mice that developed scrapie in ∼165 days, suggesting that wt MoPrP acts in trans to accelerate replication of RML106 prions. Purified PrP Sc106 was protease resistant, formed filaments, and was insoluble in nondenaturing detergents. The unique features of RML106 prions offer insights into the mechanism of prion replication, and the small size of PrP Sc106 should facilitate structural analysis.