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Updated: Jul 1, 2026
Procedures for Identifying Infectious Prions After Passage Through the Digestive System of an Avian Species
Published on: November 6, 2013
Quantitative recovery of scrapie agent with minimal protein from highly infectious cultures
1Section of Neuropathology, Yale Medical School, New Haven, Connecticut 06510, USA.
Abstract:
There are few reports on the isolation, quantitative recovery, and relative purification of infectious particles that cause scrapie, Creutzfeldt-Jakob disease (CJD) and epidemic bovine spongiform encephalopathy (BSE). Because pure prion protein (PrP) has failed to show significant infectivity, it is critical to find other molecules that are integral agent components. Only complex diseased tissues such as degenerating brain have been fractionated, and agent recoveries have been quite low in concentrated abnormal prion protein (PrP-res) preparations. To simplify the purification of infectious particles, we evaluated a monotypic cell line that continuously produced high levels of the 22L scrapie agent (N2a-22L). A new rapid and accurate GT1 culture assay was used to titrate infectivity in six representative sucrose gradients. We developed a streamlined approximately 3-h procedure that yielded full recovery of starting infectivity in fractions with only a few selected protein bands (representing <1% of starting protein). Infectious particles reproducibly sedimented through >30% sucrose steps, whereas PrP and PrP-res sedimentation varied depending on the conditions used. Both normal and abnormal PrP could be largely separated from infectivity in a single short centrifugation. Because no foreign enzymes were added to achieve reasonably purified infectious particles, these preparations may be used to elicit diagnostic antibodies to foreign agent proteins.
Insights
Researchers developed a rapid 3-hour purification method for infectious prion particles causing diseases like scrapie and bovine spongiform encephalopathy (BSE). This technique effectively separates infectious agents from normal and abnormal prion proteins (PrP and PrP-res).
Area of Science:
- Neuroscience and Prion Disease Research
- Infectious Particle Purification and Characterization
Background:
- Limited success in isolating and purifying infectious particles responsible for transmissible spongiform encephalopathies (TSEs) like scrapie, Creutzfeldt-Jakob disease (CJD), and bovine spongiform encephalopathy (BSE).
- Pure prion protein (PrP) lacks significant infectivity, highlighting the need to identify other essential agent components.
- Previous purification attempts using diseased brain tissue resulted in low agent recovery and were complicated by the presence of abnormal prion protein (PrP-res).
Purpose of the Study:
- To simplify the purification process for infectious prion particles.
- To evaluate a monotypic cell line (N2a-22L) for continuous production of the 22L scrapie agent.
- To develop a rapid and efficient method for isolating infectious particles with high recovery and purity.
Main Methods:
- Utilized a continuously scrapie-producing N2a-22L cell line to generate high levels of the 22L scrapie agent.
- Employed a novel GT1 cell culture assay for accurate titration of infectivity in sucrose gradient fractions.
- Developed and applied a streamlined, approximately 3-hour purification protocol involving sucrose gradient centrifugation.
Main Results:
- Achieved full recovery of starting infectivity in purified fractions containing minimal protein (<1% of starting material).
- Demonstrated reproducible sedimentation of infectious particles through >30% sucrose gradients.
- Successfully separated infectious particles from both normal prion protein (PrP) and abnormal prion protein (PrP-res) via short centrifugation.
Conclusions:
- The developed method offers a rapid and efficient way to purify infectious prion particles.
- The separation of infectivity from PrP and PrP-res suggests these proteins are not the sole infectious components.
- The resulting purified infectious particles, obtained without foreign enzymes, are suitable for developing diagnostic antibodies against foreign agent proteins.
