Conserved properties of human and bovine prion strains on transmission to guinea pigs.

The first transmissions of human prion diseases to rodents used guinea pigs (Gps, Cavia porcellus). Later, transgenic mice expressing human or chimeric human/mouse PrP replaced Gps, but the small size of the mouse limits some investigations. To investigate the fidelity of strain-specific prion transmission to Gps, we inoculated 'type 1' and 'type 2' prion strains into Gps, and we measured the incubation times and determined the strain-specified size of the unglycosylated, protease-resistant (r) PrP(Sc) fragment. Prions passaged once in Gps from cases of sporadic (s) Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker (GSS) disease caused by the P102L mutation were used, as well as human prions from a variant (v) CJD case, bovine prions from bovine spongiform encephalopathy (BSE) and mouse-passaged scrapie prions. Variant CJD and BSE prions transmitted to all the inoculated Gps with incubation times of 367 ± 4 and 436 ± 28 days, respectively. On second passage in Gps, vCJD and BSE prions caused disease in 287 ± 4 and 310 ± 4 days, whereas sCJD and GSS prions transmitted in 237 ± 4 and 279 ± 19 days, respectively. Although hamster Sc237 prions transmitted to two of three Gps after 574 and 792 days, mouse-passaged RML and 301V prion strains, the latter derived from BSE prions, failed to transmit disease to Gps. Those Gps inoculated with vCJD or BSE prions exhibited 'type 2' unglycosylated, rPrP(Sc) (19 kDa), whereas those receiving sCJD or GSS prions displayed 'type 1' prions (21 kDa), as determined by western blotting. Such strain-specific properties were maintained in Gps as well as mice expressing a chimeric human/mouse transgene. Gps may prove particularly useful in further studies of novel human prions such as those causing vCJD.