Prion diseases!

1. PRION DISEASE: AN OVERVIEW
DR GAZANFAR ABASS
VPH, IVRI-ICAR
M-5616

2. Overview
Introduction OF PRIONS
HISTORY OF PRION DISEASE
PATHOGENESIS OF PRION DISEASE
HUMAN PRION DISEASE
ANIMAL PRION DISEASE
DIAGNOSIS
Conclusions

3. PRIONS
-Stanley prusiner discovered prion in 1982 in
scrapie.
-proteinaceous infective particles.
-glycosylated specific protien of 30-KD.
-lacks of ncliec acid and doesnot produce any
inflammatory or immune reaction in the host.
-resistance to ultraviolet and standard disinfectant
and protease k.

4. THE HISTORY OF PRION
1730 Scrapie in English sheep
EUROPE
1950-kuru appear Fore people of
New Guinea
1960-demonstrating the
transmissible nature of kuru and
CJD.
1980-60-85people die from CJD
by contaminated surgical instruments
1982-Dr. Stanley Prusiner coins
the term "prion" (Proteinaceous
infectious particle).
1997-Scientists identify the
PrP gene
1986- 2000, nearly 180,000
cattle become infected
British farmers fed their cattle
an animal byproduct ( mixed
meat and bones of cattle and
sheep).

5. Functions of Prion protein
PrPC + Cu (Copper)
Antioxidant
Resistance to
oxidative stress
Prevent neuronal
dysfunction
(Brown et al., 2002)

6. CAUSES OF PRION
α-helix converted
to β-sheet structure
prion acts as a
template.
newly formed
prions triggers a
chain reaction
Aggregations of
prions-amyloid fibers
plaques

7. TRANSFORMATIONS
PrPC PrPSc

8. DIFFERENCE BETWEEN
PrPC and PrPSc
PrPC PrPSc
Solubility Soluble Non soluble
Structure Alpha-helix Beta-helix
Multimerisation Monomeric Multimeric
Infectivity Non infectious Infectious
Susceptibility to
Proteinase K
Susceptible Resistant

9. Pathogenisis of prion disease
(Adriano Aguzzi et al.,2012)

10. PRION DISEASE(TSE)
Transmissible, progressive and invariably fatal neurodegenerative
conditions associated with misfolding and aggregation of a host-
encoded cellular prion protein, PrPC.
(Imran et
al., 2011)
-also known as transmissable spongy encephalopathy.
-They have occurred in a wide range of mammalian species including human.
-Characterized by “Spongiform change” caused by intracellular vacuoles in
neurons and glia.

11. Human prion disease
Acquired
Hereditary
Sporadically
1-CJD
2-FATAL INSOMIA
3- variably protease-
sensitive prionopathy
1-familial or genetic CJD
2- fatal familial insomnia
3- Gerstmann-Sträussler-
Scheinker syndrome
1-kuru
2-iatrogenic CJD
3-variant form of
CJD .
(Bucelli RC et al.,2013)

12. Disease Host Etiology
Year of
Description
Scrapie Sheep, Goats
Infection with Prions of
unknown origin
Mid 18th century
TME Mink
Infection with Prions of
either sheep or cattle
origin
1947
CWD Cervids
Infection with Prions of
unknown origin
1967
BSE Cattle
Infection with Prions of
unknown origin
1986
FSE Cats
Infection with Prions of
BSE origin
1990
Animal prion diseases
(Jeongmin lee et al.,2013)

13. scrapie
In 1732, scrapie—disease was first reported in the UK, affecting the wool industry.
The official name for the disease (scrapie) was used from 1853 onward.
The name scrapie is derived from one of the clinical signs of the condition-
itching sensation in the animals.
CLINICAL SIGN
-excessive lip smacking
-altered gaits,
-convulsive collapse

14. In the 1900s, farmers in the UK started to feed cows with internal
organs or bones of sheep to benefit economically from the increase
in milk and meat production.
By the 1930s, other European countries and the United States
(USA) had adopted this practice. Based on the findings of
epidemiological studies on the origin of BSE, this later became the
main cause of prion disease transmission from sheep to cows across
the species barrier.
( Wilesmith JW et
al.,1991)

15. Specific risk material and the species barrier
-PrPSc in infected animals is concentrated in specific areas known as SRM.
(brain, eyes, spinal cord, skull, vertebral column, tonsils, and distal
ileum; )
-these are the most crucial areas for disease management and
control.
-The disease is transmittable via surgical tools that came into contact
with SRM.
-UK spent more than £200 million on a preventive process to protect
surgical tools against prion transmission. This shows that the
occurrence of BSE or vCJD can cause an enormous amount of
indirect expense.
(Jeongmin Lee et al.,2013)

16. -The species barrier makes it difficult for infectious diseases to be
transmitted from one species to another.
-However, a precautionary principle assumes that there is only one
value of species barrier between humans and cattle, and suggests
that the same dose that causes the disease in cattle may affect humans
in the same way. (J Appl et
al.,2006)
- The amount required to induce the disease is very small; a scientific
report submitted to the British Council in 2001 states that an amount
as small as one speck of pepper may cause the disease.
- Five grams of an oral inoculum with brain homogenate from a BSE-
infected cattle in a primate (Cynomolgus macaques) resulted in the
development of a vCJD like nuerological disease 60 months after
exposure.
-
- ( Lasmezas CI
et al.,2005)

17. BSE(bovine spongyform encephalopathy)
-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 (Hope j et al.,1988)
Neuropathology similar to Scrapie
-Vacuolation and Scrapie associated fibrils

18. Cause of BSE
Ruminant tissue in food
chain
Scrapie
Meat and bone meal
(MBM)
Sporadic BSE in
cattle
In the UK, in particular, cow intestines have been used
in MBM as a protein supplement since 1972, which
accelerated the increase of the occurrence of BSE

19. BSE
Way of infection
The cow eat offal of the infected sheep
Prions are taken up from the gut and transported
along nerve fibers to the brain stem.
Prions accumulate and convert normal prion
proteins to the disease-causing form, PrPSc.
Years later, BSE results when a sufficient number of
nerve cells have become damaged, affecting the
behaviour of the cows. And eventually the cow is dead.

20. 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

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

23. 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

24. three phases of BSE in
cattle
First phase:
- Low infectivity rate.
-Doenot threat to human.
Second phase
-high infectivity rate
-risk to public health
-symptoms not evident
to public health
The third phase:
Clinical symptoms
then death follows shortly

25. Cattle affected by BSE
experience progressive
degeneration of the
nervous system

26. How did BSE Transfer to Humans
Sheep with Scrapie used in Meat and Bone Meal (MBM)
MBM fed to cattle
Infected Beef eaten by humans
Variant Creutzfeldt-Jakob disease (vCJD)

27. Creutzfeldt-Jakob disease (CJD)
Identified by Creutzfeldt and Jakob (1920)
A progressive fatal neurodegenerative disease of
unknown cause.
Characterized by seizures, massive incoordination,
dementia.
Sporadic Cruetzfeldt-Jacob disease accounts for
85% of all CJD cases with annual worldwide
incidence of 1-2 cases/million population.
(Mead S et al.,2003)

28.  Variant Creutzfeldtt-Jakob Disease (vCJD), is
caused by the consumption of BSE infected
meat products
 First 10 cases of variant CJD were observed
in 1996, ten years after the outbreak of BSE in
the UK
 Variant CJD seems to affect mostly young patients below
30 year.
Variant Creutzfeldtt-Jakob Disease (vCJD),

29. COUNTRY CDC REPORT (OCT. 2009) WHO
REPORT(FEB.2012)
UNITED KINGDOM 170 175
FRANCE 25 25
ITALY 2 2
SPAIN 5 5
IRELAND 4 4
UNITED STATES 3 3
NETHERLAND 3 3
PORTUGAL 2 2
CANADA 1 2
JAPAN 1 1
SAUDI ARABIA 1 1
TAIWAN - 1
Epidemiology of VCJD

30. KURU
Kuru is the first human prion disease that was shown to be transmissible to chimpanzees by
intracerebral introduction of brain homogenates from kuru patients.
(Gajdusek DC et al.,1966)
-Fore linguistic group of Papua New Guinea .
-Etiology- ritualistic cannibalism.
-Women and young children were more exposed to the risk material than adult man..
- kuru epidemic killed 1-2% of the population at its peak.
-With a ban on ritualistic cannibalism in the mid-1950s imposed by Australian authorities, the
incidence of the disease started to decline steadily.

31. Deaths from kuru 1957–1982. Courtesy of late D. Carleton Gajdusek.

32. Kuru has 3 clinical stages
-ambulant (still can walk)
-sedentary (only can sit up),
-terminal (unable to sit up independently).
clinical signs.
-headache and pain usually in the joints of legs
-Cerebellar ataxia, tremors and and athetoid
movements are distinctive
-Shivering amplifiable by cold was the symptom
on the basis of which the disease was named "kuru.

33. Different prions affect different regions of the
brain
Cerebral cortex: the symptoms include
loss of memory and mental acuity, also
visual imparement (CJD).
Thalamus: Fatal Familial Insomnia (FFI).
Cerebellum: lose the control of body
movements and difficulties to walk
(kuru, GSS).
Brain stem: In the mad cow disease
(BSE), the brain stem is affected.

34. Diagnostic Methods
At present, a reliable diagnosis of prion disease is possible only through
autopsy since there is no approved method for detecting prion levels, which
are too low to be detected by any test, in the peripheral nervous systems of
live animals or humans.
The standard diagnosis procedures for BSE suggested by the OIE
-ELISA
-Western blotting
-immunohistochemical method
However, simple immunological tests to detect BSE cannot distinguish
PrPSc from PrPC..

35. Method
Specimen Detection of
Rapid test using ELISA Fresh brain tissue PrPSc antigen
Histopathological test Formalin fixed tissue Spongiform in brain
Immunohistochemistry FFB-tissue PrPSc antigen
Western blot Fresh brain tissue PrPSc antigen
Electron microscopy Fresh brain tissue Scrapie-associated fibril
Bioassay Fresh tissue PrPSc and infectivity
Prion detection methods for the diagnosis of BSE
(Gavier-Widen D et al.,2005)

36. BLOOD TEST
Small amount of blood is mixed with special
metal beads to which the PrPSc sticks tightly.
Washed to removed PrPC and other blood
components that could interfere with the test.
The amount of PrPSc attached to the beads
is measured using newly developed
antibodies that bind tightly to the prion
proteins.

37. CONCLUSION
•BSE and vCJD are typical emerging epidemics
•SRM is the most important aspect in controlling
•conditions or guidelines for trade” that can prevent the disease from
spreading from one country to another (SRM standards set by the
OIE )
•Risk reduction, strict precautionary principles should be applied
•Scrapie and CWD are self-sustaining epidemics and their control
necessitates the development of therapeutics that can block the
cellular spread of infectivity or the propagation of prions
Sigurdson 2007