The Generative Brain

Paraffin-embedded tissue blot (PET blot) for prion and alpha-synuclein aggregates

The PET blot is a tissue method for showing where proteinase resistant, aggregated prion protein sits in a section of brain or other tissue. Paraffin sections are mounted on a nitrocellulose membrane instead of a glass slide, digested with proteinase K, denatured and then immunostained, so only the resistant aggregate survives and the normal prion protein is removed. It was published in 2000 by Goettingen neuropathology and the federal animal virus institute in Tuebingen and works on routine formalin fixed, paraffin embedded material, including archived blocks. It has been used for confirming and mapping human CJD, for detecting PrPSc in peripheral tissues in variant CJD, for prion typing by deposition pattern, in animal TSEs, and, adapted by the same group, for alpha-synuclein aggregates in Lewy body disease. The Homburg neuropathology institute, led by the first author of the method paper, offers it as part of its prion and aggregate diagnostics. It is a post mortem or biopsy tissue test, not a test on blood or CSF. Information only, not medical advice.

Key facts

  • In the method, 5 to 7 micrometre paraffin sections from formic acid decontaminated tissue are collected on nitrocellulose, dewaxed, digested with proteinase K for 8 hours at 55 C, denatured with 3 M guanidine isothiocyanate and stained with prion protein antibodies; each section uses about 0.5 to 0.7 mg of tissue.
  • The 2000 paper reported staining in all 42 sporadic CJD brains tested, covering all codon 129 genotypes, and in none of 24 brains from other conditions such as Alzheimer disease; variant CJD, BSE and scrapie tissue was also positive.
  • In scrapie infected mice the PET blot picked up PrPSc 30 days after inoculation, when Western blot first turned positive at 120 days and the histoblot at about 60 to 90 days, well before clinical disease at about day 177.
  • The authors reported that the PET blot found PrPSc in cases where immunohistochemistry was equivocal or negative, while noting that immunohistochemistry gives better cellular detail.
  • The Edinburgh National CJD Surveillance Unit adapted the method and reported more sensitive and specific labelling than optimised immunohistochemistry in spleen, tonsil, lymph nodes and dorsal root ganglia from five variant CJD cases, and better detection in sporadic CJD brain biopsy and autopsy tissue.
  • Combined with a high sensitivity Western blot, Edinburgh found PrPSc in autopsy muscle from 8 of 17 variant, 7 of 26 sporadic and 2 of 5 iatrogenic CJD patients, with the PET blot placing the signal in nerve fibre like structures.
  • A 2009 Goettingen study used PET blot deposition maps of 20 sporadic CJD brains and 65 sheep: type 1 sporadic CJD and atypical/Nor98 scrapie showed fine synaptic grey matter deposits, while type 2 and classical scrapie showed complex deposits with white matter and brainstem involvement; a guanidine denaturation assay separated the same groups.
  • Adapted to alpha-synuclein, the PET blot revealed very many small aggregates at presynaptic terminals in dementia with Lewy bodies that standard immunohistochemistry did not show.
  • The Homburg study of 40 sporadic CJD patients found prion aggregates in ganglia other than the trigeminal ganglion only in patients with type 2 prions, and in all 17 trigeminal ganglia tested from type 2 cases.
  • The UKS Homburg diagnostics page lists PET blot on decontaminated paraffin sections together with a membrane adsorption assay and Western blot typing for prion testing, and PET blot with a microfiltration assay for aggregate diagnostics in Parkinson disease, dementia with Lewy bodies, multiple system atrophy and related disorders.
  • The same group has published PET blot work on subclinical BSE (2000) and on classical and atypical/Nor98 scrapie (2009).
  • A 2021 Homburg paper on six fatal familial insomnia brains argued that fragment size alone does not classify prion type, since the fragment matched sporadic CJD type 2 while deposition pattern and denaturation behaviour were closer to type 1.

Timeline

  1. 1999Method paper accepted by the American Journal of Pathology.
  2. 2000PET blot method published by Goettingen and Tuebingen authors; a chapter on subclinical BSE follows the same year.
  3. 2004Edinburgh surveillance unit reports improved PrPres detection in variant CJD peripheral tissues with PET blotting.
  4. 2006Edinburgh muscle study in variant, sporadic and iatrogenic CJD uses PET blot for localisation.
  5. 2007Alpha-synuclein version of the PET blot reported in dementia with Lewy bodies.
  6. 2009PET blot deposition patterns used to compare sporadic CJD types with scrapie forms.
  7. 2021Homburg peripheral ganglia study in 40 sporadic CJD patients published.
  8. 2026PET blot listed among Homburg prion and aggregate diagnostics (page read 2026-10-17).
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