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Prion Diseases powerpoint

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  • TSEs group of invariably fatal neurodegenerative diseases Associated with accumulation of protease resistant prion protein In the central dogma for these diseases, normal protease sensitive host prion (PrPc) complexes with PrPd with subsequent conversion of PrPc to protease resistant host prion (PrPd)
  • BROKEN DOWN INTO FOUR PHASES Primarily horizontal Vertical component via contact of newborns with fetal and/or other fluids
  • Western blot Protein extracted from brain homogenates Samples digested with Proteinase K, ran on denaturing polyacrylamide gel Probed with antibody F99/97.6.1 Developed by chemilumenescent detection?
  • Review slide- This slide represents the five groups of natural TSE hosts AS COMPARISONS OF GENOTYPE TO DISEASE STATUS CAN BE USED TO EXAMINE SUSCEPTIBILITY WITHIN SPECIES, WE CAN DO THE SAME COMPARISONS TO EXAMINE CROSS SPECIES TRANSMISSIBILITY BUT MUST FIRST DETERMINE THE HOST RANGE OF CWD IF WE ARE TO EXAMINE THE EFFECT OF AA POLYMORPHISMS ON CROSS SPECIES INFECTION, WE MUST FIRST DETERMINE THE HOST RANGE OF CWD SUSCEPTIBLE SPECIES 3. WHAT WE REALLY WANT TO KNOW IS-CAN CWD GO TO HUMANS, In lieu of this we must turn to other species. Studies in ruminant to ruminant transmission are ongoing Mink are a unique model because it represents a ruminant to carnivorous cycle. Then outline Scrapie and BSE, and TME history I HAVE CHOSEN TO STUDY MINK, NATURALLY SUSCEPTIBLE TO SPORADIC OUTBREAKS OF TME => SOURCE NEVER DEFINITIVELY PROVEN These include findings that BSE infects sheep and mink both orally and IC[Robinson, 1994 #166;Jeffrey, 2001 #465;Foster, 1994 #177;Foster, 2001 #14], Scrapie infects cattle and mink IC but not orally[Cutlip, 2001 #463;Cutlip, 1994 #460;Robinson, 1995 #300;Marsh, 1992 #340] TME infects cattle IC and orally but only infects sheep IC[Hadlow, 1987 #333;Robinson, 1995 #300;Marsh, 1992 #340]. Affected nuclei include DMNV, vestibular, hypoglossal, and lateral reticular
  • Review slide AS COMPARISONS OF GENOTYPE TO DISEASE STATUS CAN BE USED TO EXAMINE SUSCEPTIBILITY WITHIN SPECIES, WE CAN DO THE SAME COMPARISONS TO EXAMINE CROSS SPECIES TRANSMISSIBILITY TWO DEFICIENCIES: MUCH OF THE TRANSMISSION OCCURS BY IC ROUTE SO THEY TELL US LITTLE ABOUT NATURAL DISEASE HOST RANGE OF CWD IS STILL UNDETERMINED 3. IF WE ARE TO EXAMINE THE EFFECT OF AA POLYMORPHISMS ON CROSS SPECIES INFECTION, WE MUST FIRST DETERMINE THE HOST RANGE OF CWD SUSCEPTIBLE SPECIES I HAVE CHOSEN TO STUDY MINK, NATURALLY SUSCEPTIBLE TO SPORADIC OUTBREAKS OF TME => SOURCE NEVER DEFINITIVELY PROVEN These include findings that BSE infects sheep and mink both orally and IC[Robinson, 1994 #166;Jeffrey, 2001 #465;Foster, 1994 #177;Foster, 2001 #14], Scrapie infects cattle and mink IC but not orally[Cutlip, 2001 #463;Cutlip, 1994 #460;Robinson, 1995 #300;Marsh, 1992 #340] TME infects cattle IC and orally but only infects sheep IC[Hadlow, 1987 #333;Robinson, 1995 #300;Marsh, 1992 #340]. Affected nuclei include DMNV, vestibular, hypoglossal, and lateral reticular
  • Transcript

    • 1. Prion Diseases CMED 526/EPI 526 - May 6 th , 2009 Robert Harrington, DVM, PhD USDA – Agricultural Research Service UW – Dept. of Comparative Medicine [email_address]
    • 2. Transmissible Spongiform Encephalopathies~Prion Disease NORMAL ABNORMAL  -helix rich  -sheet rich Prusiner, et al. PrP c PrP d
    • 3. PrP Conversion PrPc PrP d Heterodimer
    • 4.  
    • 5. TSE Pathogenesis
      • Transmission occurs by oral route
      • PrP d localizes to regional lymphoid tissue
        • Transient in some species
      • Migration to central nervous system
        • Retrograde along nerves
        • Blood-borne transport
      • Accumulation in brain with subsequent neurodegeneration
    • 6. Diagnosis
      • Postmortem
        • Microscopic pathology
        • Immunohistochemistry
        • ELISA, Immunoblotting
        • Bioassay
      • Antemortem
        • Same techniques as above applied to:
        • Brain biopsy
        • Tonsil, lymph node, third eyelid biopsy, or rectal
        • ? Blood test ?
    • 7. Histology Figure 3: Photomicrographs illustrating increased diameter and density of vacuoles in TME positive IC recipient (top row, a, b, c), as compared to CWD positive IC recipient, (middle row, d, e, f) and absence of lesions in CWD negative IC recipient (bottom, row, g, h, i). Left column = cerebral cortex, middle column = hippocampus, right column = thalamus. All sections stained with hematoxylin and eosin. Bar=100 µm.
    • 8. Immunohistochemistry
    • 9. Western blot
    • 10. Animal Prion Disease
      • Scrapie - sheep, goats
      • Chronic Wasting Disease (CWD) - deer, elk, moose
      • Bovine Spongiform Encephalopathy (BSE) - cattle
      • Transmissible mink encephalopathy (TME) - mink
      • Feline spongiform encephalopathy - large & domestic cats
      • Spongiform encephalopathy of captive ungulates - exotic hoof-stock in zoological parks
    • 11. Human Prion Disease
      • Sporadic
        • Creutzfeldt-Jakob disease (CJD)
      • Familial (genetic)
        • Familial CJD
        • Gerstman-Straussler-Scheinker Syndrome (GSS)
        • Fatal Familial Insomnia (FFI)
      • Acquired by transmission
        • Kuru
        • Iatrogenic CJD (neurosurgical instruments, dura mater grafts)
        • Variant CJD (vCJD)
    • 12. Jackson, G S et al. Mol Pathol 2001;54:393-399 Human PrP Mutations
    • 13. Transmission Within Species vertical and horizontal in utero, fetal fluids, fetal membranes Foodborne Direct only through bite wounds Foodborne, blood, tissue transplant, HGH, instruments Foodborne (MBM) No direct transmission from cow to cow horizontal Oral (urine, feces, or blood?) COMMON UNCOMMON
    • 14. Species Barrier Concept
      • Transmission within a species may occur readily
      • Barrier between species limits transmission
        • Inefficient transmission
        • Extended incubation times
        • Low or non-existent rate of disease
      • Serial passage
        • Required to overcome species barrier
        • Progressive reduction in incubation time
        • Increased rate of disease
    • 15. Transmission Between Species SOURCE -> -> -> -> -> -> HOST ROUTE IC IC IC Cattle Sheep Mink Humans CWD IC IC Cattle Sheep Deer/Elk Humans TME IC IC IC Cattle Mink Deer/Elk Humans Scrapie IC; PO IC; PO IC PO Sheep Mink Deer/Elk Humans BSE
    • 16. Recognition of BSE
      • Late 1985: Unusual neurologic disease in UK cattle
      • Insidious onset
        • Irritabilty, agression
        • Motor system impairment (ataxia)
        • Difficulty in rising (e.g. “downer cow”)
        • Decreased milk production
        • Wasting
        • Death
      • Predominantly dairy cattle
        • Feeding practices
        • Relative herd age
      • Neuropathology similar to Scrapie
        • Vacuolation, PrP d , astrocytosis, Scrapie associated fibrils
    • 17. Cause of BSE
      • Ruminant tissue in food chain
        • Meat and bone meal (MBM)
        • Scrapie
        • Sporadic BSE in cattle
      • Alternative theories
        • Human tissue?
        • Toxin?
        • Environmental?
        • Other?
    • 18. BSE Epidemic
      • ~180,000 cumulative cases in UK
      • Peaked at 37,000 cases per annum in 1992
      • Recycling of ruminant tissue in food chain implicated
      • Progressive decline with introduction of feed bans
    • 19. Transmissible Spongiform Encephalopathy as a Zoonotic Disease, Brown, P., et. al. ILSI, March 2003 ( mammals )
    • 20. Spread of BSE Epidemic
      • 1990: Domestic BSE detected in Switzerland, imported cases in Portugal
      • 1999: 7 other EU countries with domestic BSE
      • Jan 2000 to Oct 2002: 11 additional EU countries
      • 2001: BSE detected in Japan
      • 2002: BSE detected in Israel
      • 2003: BSE in Canadian cow
    • 21.  
    • 22.
      • 30-40 million cattle slaughtered/year
      • 1997: ban on feeding US cattle meat-and-bone meal
      • 3 cases to date - RARE!
        • 2003: 6.5yo dairy cow imported from Canada
        • 2004: 12yo beef cow born and raised in Texas
        • 2006: 10yo beef cow in Alabama uncertain origin
        • Were there previously unrecognized cases?
      BSE in the United States
    • 23. BSE in the United States
      • 2003: Additional measures post WA BSE case
        • “ downer” cattle excluded from human consumption
        • Ban on SRM from animals > 30 months of age from human consumption
        • Ban on mechanically-separated meat
    • 24. New variant CJD
      • Unusual form of neurologic disease in teenagers and young adults
      • Spongiform encephalopathy
      • Neuropathology not consistent with sporadic forms of CJD
      • Stimulus for US National Prion Disease Center
    • 25. MM MM, MV, or VV Genetics (PRNP codon 129) -> Type 2B or 4 Type 1A PrP d isotype by Western blot -> PrP d present in tissue, especially toward late-stage disease Negative Immunohistochemical staining of tonsil or appendix tissue -> Widespread plaque staining pattern Punctate pattern PrP immunohistochemical staining pattern of brain tissue -> 100% florid plaques No amyloid plaques Histopathology of brain tissue -> Not usually elevated Usually elevated CSF 14-3-3 protein -> Hyper-intense signal in pulvinar region of the thalamus Increased signal in basal ganglia, caudate nucleus, and putamen MRI -> Nonspecific, slow Bi- or triphasic periodic complexes EEG -> Common (psychosis, depression, anxiety, apathy, withdrawal, delusions) Unusual early, Dementia later Early psychiatric symptoms -> 14 mo 4 mo Survival from date of clinical onset -> 29 yr / 28 yr 63 yr / 68 yr Average / Median age at clinical onset -> vCJD Classical sCJD vs. Clinical Feature or Procedures
    • 26. MM MM, MV, or VV Genetics (PRNP codon 129) Type 2B or 4 Type 1A PrP d isotype by Western blot PrP d present in tissue, especially toward late-stage disease Negative Immunohistochemical staining of tonsil or appendix tissue Widespread plaque staining pattern Punctate pattern PrP immunohistochemical staining pattern of brain tissue 100% florid plaques No amyloid plaques Histopathology of brain tissue 14-3-3 protein levels not usually elevated 14-3-3 protein levels usually elevated CSF Hyper-intense signal in pulvinar region of the thalamus Increased signal in basal ganglia, caudate nucleus, and putamen MRI Nonspecific, slow Bi- or triphasic periodic complexes EEG Common (psychosis, depression, anxiety, apathy, withdrawal, delusions) Unusual early, Dementia later Early psychiatric symptoms 14 mo 4 mo Length of survival from date of clinical onset 29 yr / 28 yr 63 yr / 68 yr Average / Median age at clinical onset vCJD Classical sCJD Clinical Feature or Procedures
    • 27. Percent distribution of non-iatrogenic # UK vCJD and US CJD deaths, by age group, 1995-2005 # Excludes blood transfusion-associated vCJD and pituitary hormone- or dural graft-associated CJD * UK vCJD deaths, including UK-related nonresident cases, 1995-2003 (Will, RG; personal communication, 2004) ** US CJD deaths, 1995- 2001. +
    • 28. Jackson, G S et al. Mol Pathol 2001;54:393-399 Western Blots
    • 29. BSE-vCJD Link
      • New variant disease that differs from classical CJD
        • Similarities to BSE
        • Geographically related to areas of BSE
        • Hypothesis: consumption of contaminated beef products
      • Epidemiologic curve
      • Animal challenge studies
      • Molecular biology
    • 30. BSE and vCJD Hilton , 2006. J of Pathology , 208 :134
    • 31. Goldfarb, L. G. Microbes and Infection 4 (2002) 875-882
    • 32. Animal Challenge Studies
      • BSE -> primates ≈ vCJD -> primates
        • Similar lesions and biochemistry
      • Transgenic mice
        • BSE -> humanized mice
        • vCJD -> bovinized mice
        • Lesions, biochemistry of BSE ≈ vCJD regardless of mouse type
        • Both differ from sCJD
    • 33. Jackson, G S et al. Mol Pathol 2001;54:393-399 Western Blots
    • 34. Continuing US Cattle Surveillance
      • USDA National Veterinary Services Laboratory
        • AAVLD certified labs, refer positives to NVSL
      • If 1 case per 1 million slaughter then 95% CI requires:
        • All slaughters = 2,995,731
        • Suspect cattle = 40,000 (neuro signs, fallen, “downers”)
        • 45,803 samples in 2007
        • Meets OIE “controlled risk” classification
      • National animal ID system
    • 35. Continuing US Human Surveillance
      • National Prion Disease Center
        • Established 1996
      • Monitoring for unusual trends in mortality data
      • ↑ # of autopsies in US, ↑ # of referrals
      • CJD monitoring in CWD endemic areas
    • 36.  
    • 37. CWD to Humans?
      • CJD flatline in endemic areas
      • Challenge studies indicate natural transmission is unlikely
        • Cattle
        • Mink
        • Humanized Tg mice
    • 38. CWD risk reduction?
      • Hunting
        • Avoid endemic areas
        • Test animals in effected areas
      • Consumption
        • Don’t eat brain, nerves, spleen, lymph nodes, or eyes
        • Avoid composite foods (sausage, head cheese)
    • 39. Conclusion
      • Prion diseases vary by species, distinct differences
      • TSE transmission usually limited to within a species
      • Only Scrapie and CWD are readily transmissible
      • Species barrier limits transmission between species
    • 40. Questions?
    • 41. Do you think this study supports the association of beef consumption as a primary risk factor for development of vCJD?
    • 42. Did the study authors take adequate measures to address the limitations to the study design? What other measures could they have considered?
    • 43. Are there other ways that the question of risk factors for vCJD may be addressed?

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