Follow Ups | Post Followup | Back to Discussion Board | VegSource
See spam or
inappropriate posts?
Please let us know.

From: TSS ()
Subject: SEAC epidemiology subgroup position statement on the vCJD epidemic (sporadic CJDs ???)
Date: January 26, 2006 at 9:01 am PST

Position Statement


SEAC response to the SEAC epidemiology subgroup position statement on the vCJD epidemic
SEAC welcomed and endorsed the SEAC Epidemiology Subgroup’s position statement on the vCJD epidemic1.

A substantial number of subclinical carriers of vCJD infection may exist in the UK population who cannot, at present, be identified. As a result a secondary, possibly self-sustaining, vCJD epidemic could arise due to human-to-human transmission via medical interventions such as blood transfusion and surgery. In order to implement the most appropriate precautionary measures, there is an urgent need to ascertain better the prevalence, age and genotype distribution of subclinical vCJD infection in the UK population. These data will inform assessment and subsequent management of the risks of secondary transmission.

New information on the prevalence, age and genotype distribution of vCJD infection will be provided by the planned testing of samples under collection for the National Anonymous Tonsil Archive (NATA). This testing should be progressed with urgency. However a large proportion of tonsils will be collected from young individuals with relatively low dietary exposures to BSE, and there is uncertainty about the sensitivity of tonsil tests to detect subclinical vCJD infection. It is, therefore, very important that additional programmes to test a range of tissues collected from other age groups in the population are considered.

Testing of tissues collected from autopsies could, potentially, provide substantial data on the prevalence, age and genotype distribution of infection which would complement data from NATA. However, there are practical, ethical and legal issues around post mortem testing. The committee recommends that an expert group is convened with some urgency by the Department of Health to consider and advise how such post mortem testing, or other testing designed to ascertain the prevalence, age and genotype distribution of vCJD in the UK population, might best be undertaken.

January 2006

1SEAC Epidemiology Subgroup. Position statement on the vCJD epidemic. November 2005.


Page updated: 26 January 2006

SEAC epidemiology subgroup position statement on the vCJD epidemic

1. SEAC asked the SEAC Epidemiology Subgroup to reassess the nature and future profile of the vCJD epidemic, taking into account new research and the possibility of human to human infection. SEAC identified a number of issues for the Subgroup to consider (see Annex 1).


2. Incidence of vCJD has declined over the past 4 years in the UK1,a. Projections based on the case data suggest the number of additional cases of vCJD arising from the consumption of BSE-infected material might be relatively small (less than 100)2. However, findings from a retrospective survey of appendix and tonsil tissue from operations carried out between 1995 and 2000 on individuals predominantly (83%) in the age range 10-30 years suggest that the number of infected individuals may be greater than projections based on backcalculation from vCJD cases suggest3. Furthermore, research in animal models suggests it is possible that a proportion of infections may not develop into clinical disease, or do so over a longer time scale, and remain at a subclinical level4-7. Although all vCJD cases tested to date (about 85% of cases) have been of the M/M genotype at the polymorphic codon 129 of the human prion protein gene, the effect of other genotypes on the susceptibility to, infectiousness of, and phenotype of, vCJD is uncertain. The finding of an asymptomatic case of probable blood transfusion associated transmission of vCJD of the M/V genotype8 suggests individuals of this genotype are also susceptible to secondary transmission by the intravenous route. It is possible that secondary infection via medical procedures may give rise to additional infections and potentially enable a self-sustaining secondary epidemic.

3. To address the SEAC request, the Subgroup met twice in 2005 to consider data on the epidemiology of the disease, predictions about the epidemic based on infectious disease models and relevant published and unpublished research. This initial position statement has been produced on the basis of these discussions. It is intended that the Subgroup will keep the statement under review in light of emerging scientific or medical information that improves understanding of the epidemiology of vCJD.

General observations

4. It is currently not possible to answer in full the questions set by SEAC due to continued uncertainty about key characteristics of the vCJD epidemic, in particular: the prevalence and distribution of primary and secondary infection in the UK population and incubation periods of the primary and secondary disease. Although infectious disease models provide a very useful means to test hypotheses, firm conclusions about the epidemic can only be drawn by the acquisition of better estimates of the prevalence, age and genotype distribution of infection based on population studies. Continued surveillance to identify new cases of vCJD will also provide valuable information to understand better the epidemic, in particular: trends in the incidence of vCJD, the age and genotype distribution of those who develop vCJD and identification of possible routes of secondary transmission (e.g. maternal or related to invasive medical procedures).

Influence of age on infection

5. Direct evidence to inform assessment of the influence of age on the prevalence of infection is presently limited to data from vCJD cases and the retrospective survey of appendix and tonsil tissue3. The age distribution of vCJD cases has remained relatively stable since the start of the epidemic. This is likely to be due to a combination of age-related differentials in dietary exposure to BSE and in susceptibility to the disease. Modelling studies based on the assumption that the vCJD epidemic is best defined by age-related differentials in susceptibility to vCJD together with a constant incubation period and a time window of dietary BSE exposure related directly to the observed BSE epidemic, which appears to be the most likely scenario, have produced broadly similar results9-11. These studies suggest that age-related susceptibility / exposure was greatest in the 10-20 year old age range, lower in early childhood and much lower later in adult life. However, although this profile might be expected to be reflected in the prevalence of primary infections leading to disease, it is derived from data on vCJD cases. Thus, it is possible that it may not apply to infections in the non-M/M population or to infections that remain at a subclinical level (see later).

6. Given these uncertainties, it is not possible to predict with confidence the relative risk that age groups are infected for all age groups of the population. However, it is almost surely the case that, due to the BSE control measures introduced in the UK, dietary exposure of the post-1996 birth cohorts would be very much lower or even negligible compared with older birth cohorts. Children 9 years old and younger would, therefore, very clearly be at the lowest risk of primary infection. Furthermore, despite relatively large dietary exposure to BSE9, only a single case has been observed in the pre-1940 birth cohort. This strongly suggests that adults over 66 years of age are at relatively low risk of developing primary vCJD, assuming there is no major under ascertainment of the disease in the elderly.

7. If it is assumed that susceptibility to primary vCJD infection (in terms of infections that lead to disease and infections that remain at a subclinical level) was greatest within the 10-20 year age range, it would be predicted that individuals in the 1965-1985 birth cohorts, given the peak in dietary BSE exposure around 1990, are at the greatest risk of being infected. However, as discussed above this hypothetical profile of age-related susceptibility to primary vCJD infection may not apply to the non-M/M population or to infections that remain at a subclinical level. Given the decline in the BSE epidemic, the 1990-1995 birth cohorts are at a much smaller risk, and this risk lowers progressively with year of birth. A continuing lack of vCJD cases in the post-1990 birth cohort will provide reassurance about the validity of this hypothesis.

Influence of genotype on infection

8. There is an indication that non-M/M genotypes are susceptible to vCJD infection from the case of probable blood transfusion associated transmission of vCJD of the M/V genotype8. In addition, atypical immunohistochemical results from two of the three positive appendix samples in the appendix and tonsil survey may also be an indicator of infection in non-M/M genotypes3.

9. Polymorphisms at codon 129 of the human prion protein gene influence susceptibility to, and the incubation of period of, human prion diseases12-14. Observations of kuru suggest that individuals of non-M/M genotypes are generally less susceptible to this disease and have longer incubation periods than individuals of the M/M genotype14. On the basis that these general characteristics are a valid model for vCJD infection, it seems reasonable to assume that primary and secondary vCJD cases in individuals of the M/V and V/V genotypes might arise, although they can be expected to be proportionately fewer in number and possibly appear over a long time scale. Recent projections from an infectious disease model suggest that, in the unlikely situation that other genotypes are equally susceptible to clinical disease, the number of future primary cases may increase up to five-fold compared with current estimates for future cases of the M/M genotype2.

10. It is not possible to predict the clinical phenotype of vCJD cases in non-M/M genotypes, should they arise. However, evidence from fatal familial insomnia and sporadic CJD indicates that codon 129 genotype affects clinical phenotype15,16. Experiments in transgenic mice expressing human forms of the prion protein gene suggest that the neuropathological phenotype of vCJD is influenced by genotype7.

Subclinical carriers of infection

11. Experimental studies in mice suggest primary prion infections may remain at a subclinical level but on secondary transmission result in clinical disease4,5. Thus, asymptomatic animals can be subclinical carriers of infection. The reason that infection in some animals remains at a subclinical level while clinical disease develops in others is not fully understood. The potential existence of subclinical carriers of vCJD may explain the apparent discrepancy between prevalence estimates of primary vCJD infection based on the appendix and tonsil survey and the vCJD case data. Recent projections to explore this possibility suggest the number of subclinical carriers could be of the order of several thousand2. There are currently no data to allow the possible age and genotype distribution of subclinical carriers of infection to be determined.

Additional data to understand the epidemic better

12. As discussed above, knowledge of the prevalence of infection cannot be determined accurately from quantitative models because of the uncertainties regarding the effect of genotype and age at infection and the possibility of secondary transmission from subclinical carriers of infection. Further data are required to understand better the prevalence, age and genotype distribution of both primary and secondary vCJD infection.

13. The PrPSc screening programme, due to begin in 2006, of the very large number of samples under collection for the National Anonymous Tonsil Archive (NATA) will allow more accurate assessments of the prevalence and age and genotype distribution of infection (see table). It is strongly recommended that testing of samples collected by NATA is progressed with all possible urgency.

14. However, although PrPSc tests have always proved positive in tonsils of clinical vCJD cases, there are uncertainties about the sensitivity of tonsil tests to detect asymptomatic and subclinical infection. In addition, although tonsils will be collected from a wide age range of individuals, tonsillectomy is more commonly conducted at relatively young ages. Thus, many of the samples will be collected from individuals with relatively low dietary exposures to BSE. Additional programmes to test other tissues collected from a different age distribution of individuals would provide further data as well as assurance about the findings from NATA (see table).

15. Principally as an infection control measure, a pilot study is underway to investigate the feasibility of testing the spleen, tonsil and / or appendix from cadaveric tissue / organ donors. Pilot studies to screen corneal and multi-organ donors are also under consideration. Although, testing of tissue from cadaveric, corneal and multi-organ donors might provide a limited amount of data, pilot studies to assess the feasibility of such testing are welcomed and encouraged.

16. PrPSc testing of a range of tissues collected from autopsies would, in principle, provide substantial data on the prevalence and age and genotype distribution of the section of the population presumed most likely to carry the majority of primary vCJD infections. However, such a programme relies heavily on consent for testing, which is a legal requirement, from the deceased (in life) or a close relative / carer. Practical and cost considerations around informed consent could have a substantial detrimental impact on the feasibility of such a programme. Nevertheless, it is recommended that serious consideration be given to testing samples collected from autopsies. By comparison, retrospective survey of residual appendectomy or splenectomy tissues, although informative, would be less useful (see table).

17. It is also recommended that enhanced clinical surveillance in the elderly be considered (see table). Although vCJD cases arising from primary transmission of BSE are observed mostly in young adults, there may be potential under-ascertainment of cases in the elderly, possibly due to misdiagnosis. Enhanced surveillance of this section of the population would allow this possibility to be tested. Furthermore, such enhanced surveillance would provide additional assurance that clinical cases of secondary transmission of vCJD may be detected since this section of the population is the group most likely to have undergone invasive medical procedures and / or to have received blood transfusions. Should cases be detected in older age groups, it would be important to undertake statistical analyses to estimate the proportion of cases that might have arisen from the dietary route versus medical interventions, i.e. the proportion of disease that could have arisen from primary or secondary transmission.

18. Clinical monitoring and, with patient consent, post mortem vCJD tests on individuals considered to be ‘at risk of vCJD for public health purposes’ would help to inform assessment of secondary transmission risks. Proposals are currently being developed for blood component recipients and should be considered for all at risk groups.

Self-sustaining epidemic

19. Current risk assessments of secondary transmission through surgery, blood transfusion, dentistry and bone / tissue / organ transplantation17 suggest that, on the basis of what is presently known, transmission via the surgical and blood routes are the most important in terms of the possible contribution to a secondary epidemic. This is on the basis of the relatively high number of surgical procedures and blood transfusions and estimated transmission efficiencies via these routes. By comparison, the risk of transmission via dentistry per procedure is thought to be relatively low, although the number of procedures is relatively large. In contrast, the risk of transmission via transplantation, depending on what tissues / organs are transplanted, is thought to be relatively high but the number of procedures is relatively low. However, uncertainties in key parameters in the risk assessments remain, such as the profile of the primary epidemic, infectivity levels in tissues, transmission efficiencies via routes and the effectiveness of decontamination / infectivity reduction methods.

20. The information currently available from follow up of children born to vCJD cases cannot exclude the possibility of maternal transmission of vCJD. However, on the basis of the information available on prion diseases of humans and animals, maternal transmission of vCJD, if it occurs, is unlikely on its own to support a self-sustaining secondary epidemic.

21. On the basis of current understanding, the transmission risk from the surgical route on its own could create a self-sustaining epidemic under worst case conditions of long incubation period for iatrogenic vCJD and long patient survival times. The National Institute for Health and Clinical Excellence is currently conducting an assessment of precautionary measures to reduce potential transmission risks via surgery. Blood borne transmission on its own is thought unlikely to result in a self-sustaining epidemic, especially given the precautionary measures already enacted (e.g. (deferral of donations from blood recipients, import of plasma for fractionation and leucodepletion). The large number of dental procedures (coupled with good patient survival) implies that any significant risk via that route could have a major impact on the dynamics of secondary infection. In addition, interactions between routes of transmission will also make a self-sustaining epidemic more likely.

22. The likelihood of a self-sustaining epidemic cannot be quantified at present. The complexity and number of interactions between potential routes of transmission make development of a workable model to quantify interactions within and between routes and the effect interactions might have on transmission risks very difficult. Work is underway to develop population level models for the surgical and blood routes with a view to developing a combined model to explore the effect of interactions between these routes. This work should continue to be supported.

23. On the basis of current risk assessments of transmission routes considered in isolation, factors such as the number of potential transmissions, infectivity of tissues, the efficiencies of transmission and the effectiveness of decontamination / infectivity reduction methods are all, to varying extents, key influences on the likelihood of a self-sustaining epidemic arising and the rate that it might develop.

24. On the basis of current understanding, a secondary epidemic is more likely if many individuals are exposed to potentially infectious material from a single individual (e.g. through dispersion of surgical instruments between sets) or vice versa (e.g. if blood products are pooled, exposing each recipient to multiple donors). A secondary epidemic is also generally more likely if patients who have undergone one potentially infectious procedure are at increased risk of undergoing further procedures.

SEAC Epidemiology Subgroup November 2005

a Number of deaths from vCJD in the UK in the years 1999 to 2005: 15 (1999), 28 (2000), 20 (2001), 17 (2002), 18 (2003), 9 (2004) and 3 (end September 2005).


Table of potential investigative programmes to improve understanding of the vCJD epidemic (27 KB)


2. Clarke & Ghani (2005) Projections of future course of the primary vCJD epidemic in the UK: inclusion of subclinical infection and the possibility of wider genetic susceptibility R. J. Soc. Interface. 2, 19-31.

3. Hilton et al. (2004) Prevalence of lymphoreticular prion protein accumulation in UK tissue samples. J Pathol. 203, 733-739.

4. Hill et al. (2000) Species-barrier-independent prion replication in apparently resistant species. Proc. Natl. Acad. Sci. USA. 97, 10248-10253.

5. Race et al. (2001) Long-term subclinical carrier state precedes scrapie replication and adaptation in a resistant species: analogies to bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease. J Virol. 75, 10106-10112.

6. Asante et al. (2002) BSE prions propagate as either variant CJD-like or sporadic CJD-like prion strains in transgenic mice expressing human prion protein. EMBO J. 21, 6358-6366.

7. Wadsworth et al. (2004) Human prion protein V129 prevents expression of variant CJD phenotype. Science. 306, 1793-1796.

8. Peden et al. (2004) Preclinical vCJD after blood transfusion in a PRNP codon 129 heterozygous patient. Lancet. 364, 477-479.

9. Cooper & Bird (2003) Predicting incidence of variant Creutzfeldt-Jakob disease from UK dietary exposure to bovine spongiform encephalopathy for the 1940 to 1969 and post-1969 birth cohorts. Int. J. Epidemiol. 32, 784-791.

10. Ghani et al. (2003) Updated projections of future vCJD deaths in the UK. BMC Infect. Dis. 3, 4-11.

11. Boelle et al. (2004) Epidemiological evidence of higher susceptibility to vCJD in the young. BMC Infect Dis. 4, 26-32.

12. Alperovitch et al. (1999) Codon 129 prion protein genotype and sporadic Creutzfeldt-Jakob disease. Lancet 353, 1673-1674.

13. Huillard d’Aignaux et al. (1999) Incubation period of Creutzfeldt-Jakob disease in human growth hormone recipients in France. Neurology 53, 1197-1201.

14. Lee et al. (2001) Increased susceptibility to kuru of carriers of the PRNP 129 methionine/methionine genotype. J. Infect. Disease. 183, 192-196.

15. Gambetti et al. (1995) Fatal familial insomnia and familial Creutzfeldt-Jakob disease: clinical, pathological and molecular features. Brain Pathol. 5, 43-51.

16. Parchi et al. (1999) Classification of sporadic Creutzfeld-Jakob disease based on molecular and phenotypic analysis of 300 subjects. Ann. Neurol. 46, 224-233.

17. Economics and Operational Research Division risk assessments, Department of Health.

Annex 1
Issues SEAC asked the SEAC Epidemiology Subgroup to consider:

1. What are the implications of recent research for current models of the vCJD epidemic?

(a) Do recent data on age- and genotype-related effects alter the predicted profile of the vCJD epidemic and the potential number of infective carriers?

(b) Are there likely to be 'carriers' of infectivity who do not develop clinical vCJD within their lifetime, or who present with clinical features not currently recognised as vCJD, and if so, what are the limits on the possible prevalence / age distribution / genotype of such individuals?

2. What new evidence would lead SEAC to believe that the size of the vCJD epidemic is likely to be larger or smaller than current estimates (i.e. what new data would lead SEAC to believe that current estimates may be incorrect)?

(a) Are the current and expected data from population level studies (i.e. tonsil and appendix and other tissue surveys) sufficient to enable estimation of the age / genotype distribution of infection, and what further information would help inform predictions of the profile of the vCJD epidemic?

(b) What are the information barriers to determining the potential risks to public health from carriers of vCJD infectivity?

3. Is there a significant risk of a self-sustaining human vCJD epidemic through secondary transmission of BSE between humans?

(a) What are the relative risks of secondary transmission through medical procedures (transfusion, transplantation, surgery)?

(b) Taking all these potential routes of transmission and their interactions into account, how likely is a self-sustaining epidemic?

(c) If a self-sustaining epidemic is possible, what factors determine its scale?

4. What are the key points at which modification of practice could significantly reduce the risk of a self-sustaining epidemic?

Page updated: 26 January 2006

SEAC seems on insisting on forgetting about the OTHER victims, the sporadic CJDs. i personally don't think they want to know. i guess they figure if they don't speak the new science and findings, we will forget. not gonna happen. my question to SEAC, why is there no concern with the other victims of this nightmare?

Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Singeltary, Sr et al.
JAMA.2001; 285: 733-734

Coexistence of multiple PrPSc types in individuals with

Creutzfeldt-Jakob disease

Magdalini Polymenidou, Katharina Stoeck, Markus
Glatzel, Martin Vey, Anne Bellon, and Adriano Aguzzi


Background The molecular typing of sporadic
Creutzfeldt-Jakob disease (CJD) is based on the size
and glycoform

ratio of protease-resistant prion protein (PrPSc), and
on PRNP haplotype. On digestion with proteinase K, type
1 and

type 2 PrPSc display unglycosylated core fragments of
21 kDa and 19 kDa, resulting from cleavage around amino

acids 82 and 97, respectively.

Methods We generated anti-PrP monoclonal antibodies to
epitopes immediately preceding the differential proteinase

K cleavage sites. These antibodies, which were
designated POM2 and POM12, recognise type 1, but not
type 2, PrPSc.

Findings We studied 114 brain samples from 70 patients
with sporadic CJD and three patients with variant CJD.

Every patient classified as CJD type 2, and all variant
CJD patients, showed POM2/POM12 reactivity in the

cerebellum and other PrPSc-rich brain areas, with a
typical PrPSc type 1 migration pattern.

Interpretation The regular coexistence of multiple
PrPSc types in patients with CJD casts doubts on the
validity of

electrophoretic PrPSc mobilities as surrogates for
prion strains, and questions the rational basis of
current CJD



The above results set the existing CJD classifications

into debate and introduce interesting questions about

human CJD types. For example, do human prion types

exist in a dynamic equilibrium in the brains of affected

individuals? Do they coexist in most or even all CJD

cases? Is the biochemically identified PrPSc type simply

the dominant type, and not the only PrPSc species?

Published online October 31, 2005

Detection of Type 1 Prion Protein in Variant

Creutzfeldt-Jakob Disease

Helen M. Yull,* Diane L. Ritchie,*

Jan P.M. Langeveld,? Fred G. van Zijderveld,?

Moira E. Bruce,? James W. Ironside,* and

Mark W. Head*

From the National CJD Surveillance Unit,* School of

and Clinical Medicine, University of Edinburgh, Edinburgh,

United Kingdom; Central Institute for Animal Disease

(CIDC)-Lelystad, ? Lelystad, The Netherlands; Institute
for Animal

Health, Neuropathogenesis Unit, ? Edinburgh, United Kingdom

Molecular typing of the abnormal form of the prion

protein (PrPSc) has come to be regarded as a powerful

tool in the investigation of the prion diseases. All

thus far presented indicates a single PrPSc molecular

type in variant Creutzfeldt-Jakob disease (termed

type 2B), presumably resulting from infection with a

single strain of the agent (bovine spongiform

Here we show for the first time that the PrPSc

that accumulates in the brain in variant Creutzfeldt-

Jakob disease also contains a minority type 1 component.

This minority type 1 PrPSc was found in all 21

cases of variant Creutzfeldt-Jakob disease tested,

of brain region examined, and was also

present in the variant Creutzfeldt-Jakob disease tonsil.

The quantitative balance between PrPSc types was maintained

when variant Creutzfeldt-Jakob disease was

transmitted to wild-type mice and was also found in

bovine spongiform encephalopathy cattle brain, indicating

that the agent rather than the host specifies their

relative representation. These results indicate that PrPSc

molecular typing is based on quantitative rather than

qualitative phenomena and point to a complex relationship

between prion protein biochemistry, disease phenotype

and agent strain. (Am J Pathol 2006, 168:151-157;

DOI: 10.2353/ajpath.2006.050766)



In the apparent absence of a foreign nucleic acid genome

associated with the agents responsible for transmissible

spongiform encephalopathies or prion diseases,

efforts to provide a molecular definition of agent strain

have focused on biochemical differences in the abnormal,

disease-associated form of the prion protein, termed

PrPSc. Differences in PrPSc conformation and glycosylation

have been proposed to underlie disease phenotype

and form the biochemical basis of agent strain. This

proposal has found support in the observation that the

major phenotypic subtypes of sCJD appear to correlate

with the presence of either type 1 or type 2 PrPSc in

combination with the presence of either methionine or

valine at codon 129 of the prion protein gene.2 Similarly,

the PrPSc type associated with vCJD correlates with the

presence of type 2 PrPSc and is distinct from that found in

sCJD because of a characteristically high occupancy of

both N-linked glycosylation sites (type 2B).6,11 The

means by which such conformational difference is detected

is somewhat indirect; relying on the action of proteases,

primarily proteinase K, to degrade the normal

Figure 6. Type 1 PrPSc is a stable minority component
of PrPSc from the vCJD

brain. Western blot analysis of PrP in a sample of
cerebral cortex from a

of vCJD during digestion with proteinase K is shown.
Time points assayed

are indicated in minutes (T0, 5, 10, 30, 60, 120, 180).
Duplicate blots were

probed with 3F4, which detects both type 1 and type 2
PrPSc, and with 12B2,

which detects type 1. The insert shows a shorter
exposure of the same time

course study from a separate experiment also probed
with 3F4. Both blots

included samples of cerebral cortex from a case of
sporadic CJD MM1 (Type

1) and molecular weight markers (Markers) indicate
weights in kd.

Figure 7. A minority type 1-like PrPSc is found in vCJD
tonsil, vCJD

to mice and in BSE. Western blot analysis of PrPSc in a

sample of tonsil from a case of vCJD (Tonsil), in a
concentrated brain

of a wild-type mouse (C57BL) infected with vCJD and in
a sample of cattle

BSE brain (BSE) is shown. Tissue extracts were digested
with proteinase K.

Duplicate blots were probed with either 3F4 or 6H4,
both of which detect

type 1 and type 2 PrPSc, and with 12B2, which detects
type 1. The blots

included samples of cerebral cortex from a case of
sporadic CJD MM1 (Type

1) and molecular weight markers (Markers) indicate
weights in kd.

Type 1 PrPSc in Variant Creutzfeldt-Jakob Disease 155

AJP January 2006, Vol. 168, No. 1

cellular form of PrP and produce a protease-resistant

core fragment of PrPSc that differs in the extent of its

N-terminal truncation according to the original


A complication has recently arisen with the finding that

both type 1 and type 2 can co-exist in the brains of

patients with sCJD.2,5-8 More recently this same phenomenon

has been demonstrated in patients with iatrogenically

acquired and familial forms of human prion disease.

9,10 The existence of this phenomenon is now

beyond doubt but its prevalence and its biological

remain a matter of debate.

Conventional Western blot analysis using antibodies

that detect type 1 and type 2 PrPSc has severe quantitative

limitations for the co-detection of type 1 and type 2

PrPSc in individual samples, suggesting that the prevalence

of co-occurrence of the two types might be underestimated.

We have sought to circumvent this problem by

using an antibody that is type 1-specific and applied this

to the sole remaining human prion disease where the

phenomenon of mixed PrPSc types has not yet been

shown, namely vCJD.

These results show that even in vCJD where susceptible

individuals have been infected supposedly by a

single strain of agent, both PrPSc types co-exist: a

reminiscent of that seen when similarly discriminant

antibodies were used to analyze experimental BSE in

sheep.14,17 In sporadic and familial CJD, individual

brains can show a wide range of relative amounts of the

two types in samples from different regions, but where

brains have been thoroughly investigated a predominant

type is usually evident.2,6,10 This differs from this

on vCJD, where type 1 is present in all samples

but always as a minor component that never

reaches a level at which it is detectable without a type

1-specific antibody. It would appear that the relative

between type 1 and type 2 is controlled within

certain limits in the vCJD brain. A minority type-1-like

band is also detected by 12B2 in vCJD tonsil, in BSE

brain and in the brains of mice experimentally infected

with vCJD, suggesting that this balance of types is agent,

rather than host or tissue, specific. Interestingly the

signature" of the type 2 PrPSc found in vCJD (type

2B) is also seen in the type 1 PrPSc components, suggesting

that it could legitimately be termed type 1B.

PrPSc isotype analysis has proven to be extremely

useful in the differential diagnosis of CJD and is
likely to

continue to have a major role in the investigation of human

prion diseases. However, it is clear, on the basis of

these findings, that molecular typing has quantitative

and that any mechanistic explanation of prion

replication and the molecular basis of agent strain

must accommodate the co-existence of multiple

prion protein conformers. Whether or not the different

conformers we describe here correlate in a simple and

direct way with agent strain remains to be determined. In

principle two interpretations present themselves: either

the two conformers can be produced by a single strain of

agent or vCJD (and, therefore, presumably BSE) results

from a mixture of strains, one of which generally

Evidence for the isolation in mice of more than one

strain from individual isolates of BSE has been presented


One practical consequence of our findings is that the

correct interpretation of transmission studies will depend

on a full examination of the balance of molecular types

present in the inoculum used to transmit disease, in

to a thorough analysis of the molecular types that

arise in the recipients. Another consequence relates to

the diagnostic certainty of relying on PrPSc molecular

type alone when considering the possibility of BSE

or secondary transmission in humans who have a

genotype other than methionine at codon 129 of the

PRNP gene. In this context it is interesting to note
that this

minority type 1B component resembles the type 5 PrPSc

described previously to characterize vCJD transmission

into certain humanized PRNP129VV transgenic mouse

models.12,20 This apparently abrupt change in molecular

phenotype might represent a selection process imposed

by this particular transgenic mouse model. Irrespective of

whether this proves to be the case, the results shown

here point to further complexities in the relationship

the physico-chemical properties of the prion protein,

human disease phenotype, and prion agent strain.



Type 1 PrPSc in Variant Creutzfeldt-Jakob Disease 157

AJP January 2006, Vol. 168, No. 1 ...TSS

Neuropathology and Applied Neurobiology



, 565-579 doi: 10.1111/j.1365-2990.2005.00697.x

© 2005 Blackwell Publishing Ltd


Blackwell Science, LtdOxford, UKNANNeuropathology and
Applied Neurobiology0305-1846Blackwell Publishing Ltd, 2005


Review article

Phenotypic variability in human prion diseases

J. W. Ironside, D. L. Ritchie and M. W. Head

National Creutzfeldt-Jakob Disease Surveillance Unit,
Division of Pathology, University of Edinburgh,
Edinburgh, UK

J. W. Ironside, D. L. Ritchie and M. W. Head (2005)

Neuropathology and Applied Neurobiology



Phenotypic variability in human prion diseases

Human prion diseases are rare neurodegenerative disorders

that can occur as sporadic, familial or acquired disorders.

Within each of these categories there is a wide range

of phenotypic variation that is not encountered in other

neurodegenerative disorders. The identification of the

prion protein and its key role in the pathogenesis of this

diverse group of diseases has allowed a fuller

of factors that influence disease phenotype. In particular,

the naturally occurring polymorphism at codon 129

in the prion protein gene has a major influence on the

phenotype in sporadic, familial and acquired prion

diseases, although the underlying mechanisms remain

unclear. Recent technical advances have improved our

ability to study the isoforms of the abnormal prion protein

in the brain and in other tissues. This has lead to the

of molecular strain typing, in which different isoforms

of the prion protein are proposed to correspond to

individual strains of the transmissible agent, each with

specific biological properties. In sporadic

disease there are at least six major combinations of codon

129 genotype and prion protein isotype, which appear to

relate to distinctive clinical subgroups of this disease.

However, these relationships are proving to be more complex

than first considered, particularly in cases with more

than a single prion protein isotype in the brain. Further

work is required to clarify these relationships and to

explain the mechanism of neuropathological targeting of

specific brain regions, which accounts for the diversity of

clinical features within human prion diseases.

© 2005 Blackwell Publishing Ltd, Neuropathology and
Applied Neurobiology, 31, 565-579

BSE prions propagate as either variant CJD-like or

sporadic CJD-like prion strains in transgenic mice

expressing human prion protein

The EMBO Journal Vol. 21 No. 23 pp. 6358±6366, 2002

Emmanuel A.Asante, Jacqueline M.Linehan,

Melanie Desbruslais, Susan Joiner,

Ian Gowland, Andrew L.Wood, Julie Welch,

Andrew F.Hill, Sarah E.Lloyd,

Jonathan D.F.Wadsworth and

John Collinge1

MRC Prion Unit and Department of Neurodegenerative Disease,

Institute of Neurology, University College, Queen Square,

London WC1N 3BG, UK

1Corresponding author


Variant Creutzfeldt±Jakob disease (vCJD) has been

recognized to date only in individuals homozygous for

methionine at PRNP codon 129. Here we show that

transgenic mice expressing human PrP methionine

129, inoculated with either bovine spongiform

encephalopathy (BSE) or variant CJD prions, may

develop the neuropathological and molecular phenotype

of vCJD, consistent with these diseases being

caused by the same prion strain. Surprisingly, however,

BSE transmission to these transgenic mice, in

addition to producing a vCJD-like phenotype, can also

result in a distinct molecular phenotype that is

from that of sporadic CJD with PrPSc

type 2. These data suggest that more than one BSEderived

prion strain might infect humans; it is therefore

possible that some patients with a phenotype consistent

with sporadic CJD may have a disease arising

from BSE exposure.


These studies further strengthen the evidence that vCJD

is caused by a BSE-like prion strain. Also, remarkably, the

key neuropathological hallmark of vCJD, the presence of

abundant ¯orid PrP plaques, can be recapitulated on BSE

or vCJD transmission to these mice. However, the most

surprising aspect of the studies was the ®nding that an

alternate pattern of disease can be induced in 129MM

Tg35 mice from primary transmission of BSE, with a

molecular phenotype indistinguishable from that of a

of sporadic CJD. This ®nding has important potential

implications as it raises the possibility that some humans

infected with BSE prions may develop a clinical disease

indistinguishable from classical CJD associated with type 2

PrPSc. This is, in our experience, the commonest molecular

sub-type of sporadic CJD. In this regard, it is of interest

that the reported incidence of sporadic CJD has risen
in the

UK since the 1970s (Cousens et al., 1997). This has been

attributed to improved case ascertainment, particularly as

much of the rise is reported from elderly patients and

similar rises in incidence were noted in other European

countries without reported BSE (Will et al., 1998).

However, it is now clear that BSE is present in many

European countries, albeit at a much lower incidence than

was seen in the UK. While improved ascertainment is

likely to be a major factor in this rise, that some of

additional cases may be related to BSE exposure cannot be

ruled out. It is of interest in this regard that a 2-fold

increase in the reported incidence of sporadic CJD in 2001

has recently been reported for Switzerland, a country that

had the highest incidence of cattle BSE in continental

Europe between 1990 and 2002 (Glatzel et al., 2002). No

epidemiological case±control studies with strati®cation of

CJD cases by molecular sub-type have yet been reported.

It will be important to review the incidence of sporadic

CJD associated with PrPSc type 2 and other molecular

in both BSE-affected and unaffected countries in the

light of these ®ndings. If human BSE prion infection can

result in propagation of type 2 PrPSc, it would be expected

that such cases would be indistinguishable on clinical,

pathological and molecular criteria from classical CJD. It

may also be expected that such prions would behave

biologically like those isolated from humans with sporadic

CJD with type 2 PrPSc. The transmission properties of

prions associated with type 2 PrPSc from BSE-inoculated

129MM Tg35 mice are being investigated by serial


We consider these data inconsistent with contamination

of some of the 129MM Tg35 mice with sporadic CJD

prions. These transmission studies were performed according

to rigorous biosafety protocols for preparation of

inocula and both the inoculation and care of mice, which

are all uniquely identi®ed by sub-cutaneous transponders.

However, crucially, the same BSE inocula have been used

on 129VV Tg152 and 129MM Tg45 mice, which are

highly sensitive to sporadic CJD but in which such

transmissions producing type 2 PrPSc were not observed.

Furthermore, in an independent experiment, separate

inbred lines of wild-type mice, which are highly resistant

to sporadic CJD prions, also propagated two distinctive

PrPSc types on challenge with either BSE or vCJD. No

evidence of spontaneous prion disease or PrPSc has been

seen in groups of uninoculated or mock-inoculated aged

129MM Tg35 mice.

While distinctive prion isolates have been derived from

BSE passage in mice previously (designated 301C and

301V), these, in contrast to the data presented here, are

propagated in mice expressing different prion proteins

(Bruce et al., 1994). It is unclear whether our ®ndings

indicate the existence of more than one prion strain in

individual cattle with BSE, with selection and preferential

replication of distinct strains by different hosts, or that

`mutation' of a unitary BSE strain occurs in some types of

host. Western blot analysis of single BSE isolates has not

shown evidence of the presence of a proportion of

monoglycosylated dominant PrPSc type in addition to the

diglycosylated dominant pattern (data not shown).

Extensive strain typing of large numbers of individual

BSE-infected cattle either by biological or molecular

methods has not been reported.

Presumably, the different genetic background of the

different inbred mouse lines is crucial in determining

which prion strain propagates on BSE inoculation. The

transgenic mice described here have a mixed genetic

background with contributions from FVB/N, C57BL/6 and

129Sv inbred lines; each mouse will therefore have a

different genetic background. This may explain the

differing response of individual 129MM Tg35 mice, and

the difference between 129MM Tg35 and 129MM Tg45

mice, which are, like all transgenic lines, populations

derived from single founders. Indeed, the consistent

distinctive strain propagation in FVB and C57BL/6 versus

SJL and RIIIS lines may allow mapping of genes relevant

to strain selection and propagation, and these studies
are in


That different prion strains can be consistently isolated

in different inbred mouse lines challenged with BSE

prions argues that other species exposed to BSE may

develop prion diseases that are not recognizable as being

caused by the BSE strain by either biological or molecular

strain typing methods. As with 129MM Tg35 mice, the

prions replicating in such transmissions may be

from naturally occurring prion strains. It

remains of considerable concern whether BSE has transmitted

to, and is being maintained in, European sheep

¯ocks. Given the diversity of sheep breeds affected by

scrapie, it has to be considered that some sheep might have

become infected with BSE, but propagated a distinctive

strain type indistinguishable from those of natural sheep

scrapie. ...

The EMBO Journal Vol. 21 No. 23 pp. 6358±6366, 2002

6358 ãEuropean Molecular Biology Organization

J Neuropsychiatry Clin Neurosci 17:489-495, November 2005
doi: 10.1176/appi.neuropsych.17.4.489
© 2005 American Psychiatric Publishing, Inc.

Psychiatric Manifestations of Creutzfeldt-Jakob
Disease: A 25-Year Analysis
Christopher A. Wall, M.D., Teresa A. Rummans, M.D.,
Allen J. Aksamit, M.D.,
Lois E. Krahn, M.D. and V. Shane Pankratz, Ph.D.
Received April 20, 2004; revised September 9, 2004;
accepted September 13,
2004. From the Mayo Clinic, Department of Psychiatry
and Psychology,
Rochester, Minnesota; Mayo Clinic, Department of
Neurology, Rochester,
Minnesota. Address correspondence to Dr. Wall, Mayo
Clinic, Department of
Psychiatry and Psychology, Mayo Building-W11A, 200
First St., SW, Rochester,
MN 55905; (E-mail).

This study characterizes the type and timing of
psychiatric manifestations
in sporadic Creutzfeldt-Jakob disease (sCJD).
Historically, sCJD has been
characterized by prominent neurological symptoms, while
the variant form
(vCJD) is described as primarily psychiatric in
presentation and course: A
retrospective review of 126 sCJD patients evaluated at
the Mayo Clinic from
1976-2001 was conducted. Cases were reviewed for
symptoms of depression,
anxiety, psychosis, behavior dyscontrol, sleep
disturbances, and
neurological signs during the disease course. Eighty
percent of the cases
demonstrated psychiatric symptoms within the first 100
days of illness, with
26% occurring at presentation. The most commonly
reported symptoms in this
population included sleep disturbances, psychotic
symptoms, and depression.
Psychiatric manifestations are an early and prominent
feature of sporadic
CJD, often occurring prior to formal diagnosis.



Historically, psychiatric manifestations have been
described as a relatively
infrequent occurrence in the sporadic form of
creutzfeldt-Jakob disease.
However, our findings suggest otherwise. In this study,
a vast majority of
the cases were noted to have at least one psychiatric
symptom during the
course of illness, with nearly one-quarter occurring in
the prodromal or
presenting phase of the illness. After comparing the
frequency of
neuropsychiatric symptoms in sporadic CJD to studies
describing the variant
form of CJD, we found that there are fewer clinical
differences than
previously reported.5-7 While the age of patients
with vCJD presentation
is significantly younger and the course of illness is
longer, the type and
timing of psychiatric manifestations appear similar
between these two
diseases. ...snip...

Personal Communication

-------- Original Message --------

Subject: re-BSE prions propagate as

either variant CJD-like or sporadic CJD Date: Thu, 28
Nov 2002 10:23:43

-0000 From: "Asante, Emmanuel A" To:

Dear Terry,

I have been asked by Professor Collinge to respond to
your request. I am

a Senior Scientist in the MRC Prion Unit and the lead
author on the

paper. I have attached a pdf copy of the paper for your
attention. Thank

you for your interest in the paper.

In respect of your first question, the simple answer
is, yes. As you

will find in the paper, we have managed to associate
the alternate

phenotype to type 2 PrPSc, the commonest sporadic CJD.

It is too early to be able to claim any further
sub-classification in

respect of Heidenhain variant CJD or Vicky Rimmer's
version. It will

take further studies, which are on-going, to establish
if there are

sub-types to our initial finding which we are now
reporting. The main

point of the paper is that, as well as leading to the
expected new

variant CJD phenotype, BSE transmission to the
129-methionine genotype

can lead to an alternate phenotype which is
indistinguishable from type

2 PrPSc.

I hope reading the paper will enlighten you more on the
subject. If I

can be of any further assistance please to not hesitate
to ask. Best wishes.

Emmanuel Asante

<> ____________________________________

Dr. Emmanuel A Asante MRC Prion Unit & Neurogenetics
Dept. Imperial

College School of Medicine (St. Mary's) Norfolk Place,

Tel: +44 (0)20 7594 3794 Fax: +44 (0)20 7706 3272 email: (until 9/12/02)

New e-mail: (active from now)


Human Prion Protein with

Valine 129 Prevents Expression

of Variant CJD Phenotype

Jonathan D. F. Wadsworth, Emmanuel A. Asante,

Melanie Desbruslais, Jacqueline M. Linehan, Susan Joiner,

Ian Gowland, Julie Welch, Lisa Stone, Sarah E. Lloyd,

Andrew F. Hill,* Sebastian Brandner, John Collinge.

Variant Creutzfeldt-Jakob disease (vCJD) is a unique
and highly distinctive

clinicopathological and molecular phenotype of human
prion disease

associated with infection with bovine spongiform
encephalopathy (BSE)-like

prions. Here, we found that generation of this
phenotype in transgenic mice

required expression of human prion protein (PrP) with
methionine 129.

Expression of human PrP with valine 129 resulted in a
distinct phenotype and,

remarkably, persistence of a barrier to transmission of
BSE-derived prions on

subpassage. Polymorphic residue 129 of human PrP
dictated propagation of

distinct prion strains after BSE prion infection. Thus,
primary and secondary

human infection with BSE-derived prions may result in
sporadic CJD-like or

novel phenotypes in addition to vCJD, depending on the
genotype of the prion

source and the recipient.



Characterization of two distinct prion strains

derived from bovine spongiform encephalopathy

transmissions to inbred mice



Follow Ups:

Post a Followup

E-mail: (optional)


Optional Link URL:
Link Title:
Optional Image URL: