prion diseases powerpoint

Prion Diseases

CMED 526/EPI 526 - May 6th, 2009

Robert Harrington, DVM, PhDUSDA – Agricultural Research ServiceUW – Dept. of Comparative Medicine

rdhdvm@u.washington.edu

Transmissible Spongiform Encephalopathies~Prion DiseaseTransmissible Spongiform Encephalopathies~Prion Disease

NORMAL ABNORMAL

-helix rich -sheet rich

Prusiner, et al.

PrPc PrPd

PrP ConversionPrP Conversion

PrPc PrPd

Heterodimer

TSE PathogenesisTSE Pathogenesis• Transmission occurs by oral routeTransmission occurs by oral route

• PrPPrPdd localizes to regional lymphoid localizes to regional lymphoid tissuetissue– Transient in some species Transient in some species

• Migration to central nervous systemMigration to central nervous system– Retrograde along nervesRetrograde along nerves– Blood-borne transportBlood-borne transport

• Accumulation in brain with subsequent Accumulation in brain with subsequent neurodegenerationneurodegeneration

DiagnosisDiagnosis• PostmortemPostmortem

– Microscopic pathologyMicroscopic pathology– ImmunohistochemistryImmunohistochemistry– ELISA, ImmunoblottingELISA, Immunoblotting– BioassayBioassay

• AntemortemAntemortem– Same techniques as above applied to:Same techniques as above applied to:– Brain biopsyBrain biopsy– Tonsil, lymph node, third eyelid biopsy, or Tonsil, lymph node, third eyelid biopsy, or

rectalrectal– ? Blood test ?? Blood test ?

Histology Histology

ImmunohistochemistryImmunohistochemistry

Western blotWestern blot

Animal Prion DiseaseAnimal Prion Disease

• ScrapieScrapie - - sheep, goatssheep, goats

• Chronic Wasting Disease (CWD)Chronic Wasting Disease (CWD) - - deer, elk, moosedeer, elk, moose

• Bovine Spongiform Encephalopathy (BSE)Bovine Spongiform Encephalopathy (BSE) - - cattlecattle

• Transmissible mink encephalopathy (TME) Transmissible mink encephalopathy (TME) - mink- mink

• Feline spongiform encephalopathyFeline spongiform encephalopathy - large & - large & domestic catsdomestic cats

• Spongiform encephalopathy of captive ungulates Spongiform encephalopathy of captive ungulates - - exotic hoof-stock in zoological parksexotic hoof-stock in zoological parks

Human Prion DiseaseHuman Prion Disease• SporadicSporadic

– Creutzfeldt-Jakob disease (CJD)Creutzfeldt-Jakob disease (CJD)

• Familial (genetic)Familial (genetic)– Familial CJDFamilial CJD– Gerstman-Straussler-Scheinker Syndrome (GSS)Gerstman-Straussler-Scheinker Syndrome (GSS)– Fatal Familial Insomnia (FFI)Fatal Familial Insomnia (FFI)

• Acquired by transmissionAcquired by transmission– Kuru Kuru – Iatrogenic CJD (neurosurgical instruments, dura Iatrogenic CJD (neurosurgical instruments, dura

mater grafts)mater grafts)– Variant CJD (vCJD)Variant CJD (vCJD)

Jackson, G S et al. Mol Pathol 2001;54:393-399

Human PrP MutationsHuman PrP Mutations

vertical and horizontalin utero, fetal fluids, fetal membranes

FoodborneDirect only through bite wounds

Foodborne, blood, tissue transplant, HGH, instruments

Foodborne (MBM)No direct transmission

from cow to cow

horizontalOral (urine, feces, or blood?)

CO

MM

ON

UN

CO

MM

ON

Transmission Within SpeciesTransmission Within Species

Species Barrier ConceptSpecies Barrier Concept• Transmission Transmission withinwithin a species may occur a species may occur

readilyreadily

• Barrier Barrier betweenbetween species limits transmission species limits transmission– Inefficient transmissionInefficient transmission– Extended incubation timesExtended incubation times– Low or non-existent rate of diseaseLow or non-existent rate of disease

• Serial passageSerial passage– Required to overcome species barrierRequired to overcome species barrier– Progressive reduction in incubation timeProgressive reduction in incubation time– Increased rate of diseaseIncreased rate of disease

BSEBSE SheepSheep

MinkMink

Deer/ElkDeer/Elk

HumansHumans

IC; IC; POPO

IC; IC; POPO

ICIC

POPO

ScrapieScrapie CattleCattle

MinkMink

Deer/ElkDeer/Elk

HumansHumans

ICIC

ICIC

ICIC

TMETME CattleCattle

SheepSheep

Deer/ElkDeer/Elk

HumansHumans

ICIC

ICIC

CWDCWD CattleCattle

SheepSheep

MinkMink

HumansHumans

ICIC

ICIC

ICIC

SOURCE → → → → → → HOST ROUTE

Transmission Between SpeciesTransmission Between Species

Recognition of BSERecognition of BSE• Late 1985: Unusual neurologic disease in UK Late 1985: Unusual neurologic disease in UK

cattlecattle• Insidious onsetInsidious onset

– Irritabilty, agressionIrritabilty, agression– Motor system impairment (ataxia)Motor system impairment (ataxia)– Difficulty in rising (e.g. “downer cow”)Difficulty in rising (e.g. “downer cow”)– Decreased milk productionDecreased milk production– WastingWasting– DeathDeath

• Predominantly dairy cattlePredominantly dairy cattle– Feeding practicesFeeding practices– Relative herd ageRelative herd age

• Neuropathology similar to ScrapieNeuropathology similar to Scrapie– Vacuolation, PrPVacuolation, PrPdd, astrocytosis, Scrapie associated fibrils, astrocytosis, Scrapie associated fibrils

Cause of BSECause of BSE

• Ruminant tissue in food chainRuminant tissue in food chain– Meat and bone meal (MBM)Meat and bone meal (MBM)– ScrapieScrapie– Sporadic BSE in cattleSporadic BSE in cattle

• Alternative theoriesAlternative theories– Human tissue?Human tissue?– Toxin?Toxin?– Environmental?Environmental?– Other?Other?

BSE EpidemicBSE Epidemic

• ~180,000 cumulative cases in UK~180,000 cumulative cases in UK

• Peaked at 37,000 cases per annum in Peaked at 37,000 cases per annum in 19921992

• Recycling of ruminant tissue in food chain Recycling of ruminant tissue in food chain implicatedimplicated

• Progressive decline with introduction of Progressive decline with introduction of feed bansfeed bans

Transmissible Spongiform Encephalopathy as a Zoonotic Disease, Brown, P., et. al. ILSI, March 2003

(mammals)

Spread of BSE EpidemicSpread of BSE Epidemic• 1990: Domestic BSE detected in 1990: Domestic BSE detected in

Switzerland, imported cases Switzerland, imported cases in Portugalin Portugal

• 1999: 7 other EU countries with 1999: 7 other EU countries with domestic BSEdomestic BSE

• Jan 2000 to Oct 2002: 11 additional EU Jan 2000 to Oct 2002: 11 additional EU countriescountries

• 2001: BSE detected in Japan2001: BSE detected in Japan• 2002: BSE detected in Israel2002: BSE detected in Israel• 2003: BSE in Canadian cow2003: BSE in Canadian cow

• 30-40 million cattle slaughtered/year30-40 million cattle slaughtered/year

• 1997: ban on feeding US cattle meat-and-1997: ban on feeding US cattle meat-and-bone mealbone meal

• 3 cases to date - RARE!3 cases to date - RARE!– 2003: 6.5yo dairy cow imported from Canada2003: 6.5yo dairy cow imported from Canada– 2004: 12yo beef cow born and raised in Texas2004: 12yo beef cow born and raised in Texas– 2006: 10yo beef cow in Alabama uncertain 2006: 10yo beef cow in Alabama uncertain

originorigin– Were there previously unrecognized cases?Were there previously unrecognized cases?

BSE in the United StatesBSE in the United States

BSE in the United StatesBSE in the United States

• 2003: Additional measures post WA BSE 2003: Additional measures post WA BSE casecase

– ““downer” cattle excluded from human downer” cattle excluded from human consumptionconsumption

– Ban on SRM from animals Ban on SRM from animals >>30 months of age 30 months of age from human consumptionfrom human consumption

– Ban on mechanically-separated meatBan on mechanically-separated meat

New variant CJDNew variant CJD

• Unusual form of neurologic disease in Unusual form of neurologic disease in teenagers and young adultsteenagers and young adults

• Spongiform encephalopathySpongiform encephalopathy

• Neuropathology not consistent with Neuropathology not consistent with sporadic forms of CJDsporadic forms of CJD

• Stimulus for US National Prion Stimulus for US National Prion Disease CenterDisease Center

Clinical Feature or Clinical Feature or ProceduresProcedures

Classical sCJD vs.Classical sCJD vs. vCJDvCJD

Average / Median age at clinical Average / Median age at clinical onsetonset→→

63 yr / 68 yr63 yr / 68 yr 29 yr / 28 yr29 yr / 28 yr

Survival from date of clinical onset Survival from date of clinical onset →→

4 mo4 mo 14 mo14 mo

Early psychiatric symptoms Early psychiatric symptoms →→ Unusual early,Unusual early,Dementia laterDementia later

Common (psychosis, Common (psychosis, depression, anxiety, depression, anxiety, apathy, withdrawal, apathy, withdrawal, delusions)delusions)

EEG EEG →→ Bi- or triphasic periodic Bi- or triphasic periodic complexescomplexes

Nonspecific, slowNonspecific, slow

MRI MRI →→ Increased signal in basal Increased signal in basal ganglia, caudate ganglia, caudate nucleus, and putamennucleus, and putamen

Hyper-intense signal in Hyper-intense signal in pulvinar region of the pulvinar region of the thalamusthalamus

Genetics (PRNP codon 129) Genetics (PRNP codon 129) →→ MM, MV, or VVMM, MV, or VV MMMM

CSF 14-3-3 protein CSF 14-3-3 protein →→ Usually elevatedUsually elevated Not usually elevatedNot usually elevated

Histopathology of brain tissue Histopathology of brain tissue →→ No amyloid plaquesNo amyloid plaques 100% florid plaques100% florid plaques

PrP immunohistochemical staining PrP immunohistochemical staining pattern of brain tissue pattern of brain tissue →→

Punctate patternPunctate pattern Widespread plaque staining Widespread plaque staining patternpattern

Immunohistochemical staining of Immunohistochemical staining of tonsil or appendix tissue tonsil or appendix tissue →→

NegativeNegative PrPPrPdd present in tissue, present in tissue, especially toward late-stage especially toward late-stage diseasedisease

PrPPrPdd isotype by Western blot isotype by Western blot →→ Type 1AType 1A Type 2B or 4Type 2B or 4

Clinical Feature or ProceduresClinical Feature or Procedures Classical sCJDClassical sCJD vCJDvCJD

Average / Median age at clinical Average / Median age at clinical onsetonset

63 yr / 68 yr63 yr / 68 yr 29 yr / 28 yr29 yr / 28 yr

Length of survival from date of Length of survival from date of clinical onsetclinical onset

4 mo4 mo 14 mo14 mo

Early psychiatric symptomsEarly psychiatric symptoms Unusual early,Unusual early,Dementia laterDementia later

Common (psychosis, Common (psychosis, depression,depression,

anxiety, apathy, withdrawal, anxiety, apathy, withdrawal, delusions)delusions)

EEGEEG Bi- or triphasic periodic Bi- or triphasic periodic complexescomplexes

Nonspecific, slowNonspecific, slow

MRIMRI Increased signal in basal Increased signal in basal ganglia, caudate nucleus, ganglia, caudate nucleus, and putamenand putamen

Hyper-intense signal in Hyper-intense signal in pulvinar region of the pulvinar region of the thalamusthalamus

Genetics (PRNP codon 129)Genetics (PRNP codon 129) MM, MV, or VVMM, MV, or VV MMMM

CSFCSF 14-3-3 protein levels usually 14-3-3 protein levels usually elevatedelevated

14-3-3 protein levels not 14-3-3 protein levels not usually elevatedusually elevated

Histopathology of brain tissueHistopathology of brain tissue No amyloid plaquesNo amyloid plaques 100% florid plaques100% florid plaques

PrP immunohistochemical staining PrP immunohistochemical staining pattern of brain tissuepattern of brain tissue

Punctate patternPunctate pattern Widespread plaque staining Widespread plaque staining patternpattern

Immunohistochemical staining of Immunohistochemical staining of tonsil or appendix tissuetonsil or appendix tissue

NegativeNegative PrPPrPdd present in tissue, present in tissue, especially toward late-especially toward late-stage diseasestage disease

PrPPrPdd isotype by Western blot isotype by Western blot Type 1AType 1A Type 2B or 4Type 2B or 4

0

5

10

15

20

25

30

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

Five-year age group at death

Per

cen

t

UK vCJD* (n=140)

US CJD** (n=1,816)

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.

+

Jackson, G S et al. Mol Pathol 2001;54:393-399

Western BlotsWestern Blots

BSE-vCJD LinkBSE-vCJD Link

• New variant disease that differs from classical CJDNew variant disease that differs from classical CJD– Similarities to BSESimilarities to BSE– Geographically related to areas of BSEGeographically related to areas of BSE– Hypothesis: consumption of contaminated beef productsHypothesis: consumption of contaminated beef products

• Epidemiologic curveEpidemiologic curve

• Animal challenge studiesAnimal challenge studies

• Molecular biologyMolecular biology

BSE and vCJDBSE and vCJD

Hilton, 2006. J of Pathology, 208:134

Goldfarb, L. G. Microbes and Infection 4 (2002) 875-882

Animal Challenge StudiesAnimal Challenge Studies

• BSE BSE → primates ≈ vCJD → primates→ primates ≈ vCJD → primates– Similar lesions and biochemistrySimilar lesions and biochemistry

• Transgenic miceTransgenic mice– BSE BSE → humanized mice→ humanized mice– vCJD → bovinized mice vCJD → bovinized mice – Lesions, biochemistry of BSE ≈ vCJD Lesions, biochemistry of BSE ≈ vCJD

regardless of mouse typeregardless of mouse type– Both differ from sCJD Both differ from sCJD

Jackson, G S et al. Mol Pathol 2001;54:393-399

Western BlotsWestern Blots

Continuing US Cattle Continuing US Cattle SurveillanceSurveillance• USDA National Veterinary Services LaboratoryUSDA National Veterinary Services Laboratory

– AAVLD certified labs, refer positives to NVSLAAVLD certified labs, refer positives to NVSL

• If 1 case per 1 million slaughter then 95% CI If 1 case per 1 million slaughter then 95% CI requires:requires:

– All slaughters = 2,995,731 All slaughters = 2,995,731

– Suspect cattle = 40,000 (neuro signs, fallen, “downers”)Suspect cattle = 40,000 (neuro signs, fallen, “downers”)

– 45,803 samples in 200745,803 samples in 2007

– Meets OIE “controlled risk” classificationMeets OIE “controlled risk” classification

• National animal ID systemNational animal ID system

Continuing US Human Continuing US Human SurveillanceSurveillance

• National Prion Disease CenterNational Prion Disease Center– Established 1996Established 1996

• Monitoring for unusual trends in Monitoring for unusual trends in mortality datamortality data

• ↑↑ # of autopsies in US, # of autopsies in US, ↑ # of referrals↑ # of referrals

• CJD monitoring in CWD endemic areasCJD monitoring in CWD endemic areas

CWD to Humans?CWD to Humans?

• CJD flatline in endemic areasCJD flatline in endemic areas

• Challenge studies indicate natural Challenge studies indicate natural transmission is unlikelytransmission is unlikely– CattleCattle– MinkMink– Humanized Tg miceHumanized Tg mice

CWD risk reduction?CWD risk reduction?

• HuntingHunting– Avoid endemic areasAvoid endemic areas– Test animals in effected areasTest animals in effected areas

• ConsumptionConsumption– Don’t eat brain, nerves, spleen, lymph Don’t eat brain, nerves, spleen, lymph

nodes, or eyesnodes, or eyes– Avoid composite foods (sausage, head Avoid composite foods (sausage, head

cheese)cheese)

ConclusionConclusion• Prion diseases vary by species, distinct differencesPrion diseases vary by species, distinct differences

• TSE transmission usually limited to within a speciesTSE transmission usually limited to within a species

• Only Scrapie and CWD are readily transmissibleOnly Scrapie and CWD are readily transmissible

• Species barrier limits transmission between speciesSpecies barrier limits transmission between species

Questions?

Do you think this study Do you think this study supportssupportsthe association of beef the association of beef consumption as a primary risk consumption as a primary risk factor for development of factor for development of vCJD?vCJD?

Did the study authors take Did the study authors take adequate measures to address adequate measures to address the limitations to the study the limitations to the study design?design?

What other measures could What other measures could they have considered?they have considered?

Are there other ways that the Are there other ways that the question of risk factors for vCJD question of risk factors for vCJD may be addressed?may be addressed?