title: Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions.
abstract: Prions are unconventional infectious agents that cause transmissible spongiform encephalopathy (TSE) diseases, or prion diseases. The biochemical nature of the prion infectious agent remains unclear. Previously, using a protein misfolding cyclic amplification (PMCA) reaction, infectivity and disease-associated protease-resistant prion protein (PrPres) were both generated under cell-free conditions, which supported a nonviral hypothesis for the agent. However, these studies lacked comparative quantitation of both infectivity titers and PrPres, which is important both for biological comparison with in vivo-derived infectivity and for excluding contamination to explain the results. Here during four to eight rounds of PMCA, end-point dilution titrations detected a >320-fold increase in infectivity versus that in controls. These results provide strong support for the hypothesis that the agent of prion infectivity is not a virus. PMCA-generated samples caused the same clinical disease and neuropathology with the same rapid incubation period as the input brain-derived scrapie samples, providing no evidence for generation of a new strain in PMCA. However, the ratio of the infectivity titer to the amount of PrPres (specific infectivity) was much lower in PMCA versus brain-derived samples, suggesting the possibility that a substantial portion of PrPres generated in PMCA might be noninfectious.
authors: Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, Hamilton, MT 59840, USA.
authors: Mikael
authors: M
authors: Klingeborn
authors: Brent
authors: B
authors: Race
authors: Kimberly D
authors: KD
authors: Meade-White
authors: Bruce
authors: B
authors: Chesebro
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002474:Cell-Free System; D006224:Cricetinae; D015151:Immunoblotting; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D011328:Prions / Q000378:metabolism* / Q000472:pathogenicity*; D011489:Protein Denaturation; D017510:Protein Folding
chemical_list: D011328:Prions