Lack of correlation between PrPSc and infectivity in a murine model of P102L GSS

Janice Barr, Declan King, Karen Dobie, Rona Barron

Research output: Contribution to journalMeeting abstract

Abstract

The hallmark pathology of the Transmissible Spongiform Encephalopathy group of diseases has been described by vacuolation of the neurophil, gliosis and deposition of a misfolded host protein termed the prion protein (PrP). Current dogma cites the abnormal protease resistant form of this protein (PrPd) termed prions, as the sole infectious agent in this group of diseases affecting both humans and animals. Evidence from several studies apparently challenges this central role of the prion, with data demonstrating negligible detectable PrPd in the presence of high infectivity. A recent study carried out in our laboratory detected high levels of infectivity in spleen and brain of a transgenic murine model of Gerstmann-Sträussler-Scheinker (GSS/101LL) disease without a corresponding high level of PrPd deposition. Using a range of techniques such as subcellular fractionation studies, bioassay, proteomics, PrP detection by western blotting and immunohistochemistry including PET blots we have investigated the relationship between abnormal protein and infectivity in TSE disease processes.
We utilised a subcellular fractionation technique to establish which fractions of a GSS/101LL infected brain homogenate contained the most infectious particles and if these correlated with the presence of PrPd. Crude fractionation of a GSS/101LL murine brain homogenate determined that PrPd was found mainly in the P2 synaptosomal fraction. Further purification by differential sucrose fractionation of this P2 fraction was carried out and each fraction inoculated into groups of 101LL mice to determine infectivity levels by bioassay. These data established that there was a high level of infectivity present with no significant difference between subcellular fractions. Groups of mice injected with inoculum pre-treated with detergent did not significantly differ in titre from non-treated. Subsequent western blotting of each fraction failed to detect any level of PrP present. Differential protein expression profiling highlighted a protein peak at 10858Da which was up-regulated in infected fractions. Identification of this protein is ongoing.
Having established infectivity in the absence of detectable PrPd we sought to determine whether material from this model could convert PrPc to PrP-res(proteinase K resistant) by in vitro amplification. In a RT-QuIC conversion assay, brain homogenate from GSS/101LL transgenic mice displaying low levels of PrPd by ICC and western analysis, seeded the conversion of recombinant PrP to similar levels to that observed with models of TSE disease displaying large depositions of PrPd.
These data question the assumption that detectable/deposition of PrPd is necessarily the best biomarker of all TSE diseases and further questions the nature of the agent involved.
Original languageEnglish
Pages (from-to)60-61
JournalPrion
Volume8
Issue numberSuppt.
Publication statusPublished - 27 May 2014
EventPrion 2014 - Trieste, Italy, United Kingdom
Duration: 24 May 201430 Jun 2014

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