Lower specific infectivity of protease-resistant prion protein generated in cell-free reactions

Proc Natl Acad Sci U S A. 2011 Nov 29;108(48):E1244-53. doi: 10.1073/pnas.1111255108. Epub 2011 Nov 7.

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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Brain / metabolism*
  • Cell-Free System
  • Cricetinae
  • Immunoblotting
  • Immunohistochemistry
  • Mice
  • Mice, Transgenic
  • Nucleic Acid Amplification Techniques / methods*
  • Prions / metabolism*
  • Prions / pathogenicity*
  • Protein Denaturation*
  • Protein Folding*

Substances

  • Prions