Protective Effect of Val129-PrP against Bovine Spongiform Encephalopathy but not Variant Creutzfeldt-Jakob Disease
Natalia Fernández-Borges,1 Juan Carlos Espinosa,1 Alba Marín-Moreno, Patricia Aguilar-Calvo, Emmanuel A. Asante, Tetsuyuki Kitamoto, Shirou Mohri, Olivier Andréoletti, Juan María Torres
Bovine spongiform encephalopathy (BSE) is the only known zoonotic prion that causes variant Creutzfeldt-Jakob disease (vCJD) in humans. The major risk determinant for this disease is the polymorphic codon 129 of the human prion protein (HuPrP), where either methionine (Met129) or valine (Val129) can be encoded. To date, all clinical and neuropathologically confirmed vCJD cases have been Met129 homozygous, with the exception of 1 recently reported Met/Val heterozygous case. Here, we found that transgenic mice homozygous for Val129 Hu-PrP show severely restricted propagation of the BSE prion strain, but this constraint can be partially overcome by adaptation of the BSE agent to the Met129 Hu-PrP. In addition, the transmission of vCJD to transgenic mice homozygous for Val129 Hu-PrP resulted in a prion with distinct strain features. These observations may indicate increased risk for vCJD secondary transmission in Val129 Hu-PrP–positive humans with the emergence of new strain features.
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Discussion
We report a detailed comparison of the transmission properties of BSE and vCJD prions among humanized transgenic mice with different PRNP codon 129 genotypes. Because a high expression level of PrP in transgenic mice directly influences prion disease susceptibility and incubation time, these transgenic mice have an advantage over knock-in mice for evaluating these features in the different human PrP genotypes. In addition, the 3 mouse models used in our study have equivalent PrP expression levels, making them suitable for studying comparative susceptibilities across the different PRNP codon 129 genotypes.
In previous reports, we demonstrated that Met129 homozygous individuals might be susceptible to a sheep or goat BSE agent to a higher degree than to cattle BSE and that these agents might transmit with molecular and neuropathological properties indistinguishable from those of vCJD (31). In this study, we wanted to extend these results to the other human PRNP genotypes: Met/Val129 and Val/ Val129. We gained a different perspective when several BSE isolates adapted to different species inoculated in TgVal129 mice showed an apparent lack of transmission. In addition, almost all inoculated TgMet/Val129 mice did not transmit BSE; this finding supports the interpretation by Wadsworth et al. that human PrP Val129 severely restricts propagation of the BSE prion strain (27).
An unexpected result of this study was the finding that 1 BSE isolate from a goat (Ca-BSE/Go) was clinically transmitted to 1 of 10 TgMet/Val129 mice and subclinically transmitted to TgVal129 mice. This particular isolate is characterized by a high infectious titer (35) that could explain the potential for this inoculum to overcome the restriction on BSE prions to propagate in TgVal129 mice.
Although cattle BSE did not transmit to TgMet/Val129 mice directly, adaptation of the BSE agent to human PrP Met129 sequence and subsequent inoculation of the resultant vCJD prions to TgMet/Val129 mice produced a 100% attack rate. However, we did not detect clinical prion disease, supporting a slower rate of vCJD conversion compared with that among TgMet129 mice. This slow but potential conversion rate in TgMet/Val129 mice correlates well with the single vCJD case of a human carrying the PrP Met/Val129 genotype (22) and with the description of subclinical secondary transmissions through human vCJD–infected tissues (4–7,47).
TgVal129 mice challenged with Hu-vCJD2 did not produce detectable brain PrPres and clinical signs, in spite of the overexpression of HuPrP-Val129 and the use of the more efficient intracerebral route of infection. However, subclinical infection in these TgVal129 mice was demonstrated in BoPrP-Tg110 mice. These data suggest that PrP Val129 could sustain a very slow and limited vCJD conversion rate that is consistent with the detection of PrPres in tonsils and appendixes of asymptomatic PrP Val129 persons (23–25). Previous studies of other transgenic mice expressing PrP Val129 have also shown a low transmission efficiency of vCJD (2,27,30).
The fluctuating subclinical transmissibility of both vCJD inocula in TgVal129 mice (negative for Hu-vCJD1 and positive for Hu-vCJD2 ) might be caused by differences in prion titer between inocula. This assessment was strengthened after the transmission of both vCJDs to TgMet129 mice, in which a shorter incubation period was observed in animals inoculated with Hu-vCJD2 . A certain variability in subclinical transmissibility and incubation time between different vCJD isolates is not uncommon, as has been previously reported (2,27,30), suggesting that a Val129 transmission barrier can only be overcome with highly infectious vCJD isolates.
The dramatic changes in the susceptibility of TgVal129 mice (Table 3) challenged with vCJD isolates first passaged in TgMet129 mice suggest an apparent increase in titer of both vCJD prion isolates; however, adaptation of the inocula to the new host mouse cannot be disregarded as being partly responsible for this increased susceptibility. We observed a 100% infection rate, but without clinical signs of prion disease. We observed similar transmission features when we passaged vCJD in TgMet/Val129 mice. In addition, the apparent PrPVal129 restricted propagation of cattle BSE and BSE from other species was completely abolished after its adaptation to human PrPMet129.
Although PrP overexpression and the inoculation route can affect transmission efficiency, our results and those previously reported in both overexpressing and knock-in transgenic mice (2,27,30) suggest that the Val129 PrP variant could sustain a very slow and limited vCJD conversion rate, and is unable to completely prevent vCJD transmission. Biochemical and neuropathological features of vCJD transmission to TgVal129 mice showed substantial differences compared to TgMet129 or TgMet/ Val129 mice. Similar to previous reports (2,27,28,48), a type 5 PrPSc associated with very weak and diffuse PrP plaques without a florid morphology was the hallmark among these mice. In addition, our demonstration of previously unreported type 5 PrPSc in brain samples of vCJDchallenged knock-in Ki-Hu129V/V mice (30) establishes that the evolution of type 5 PrPSc associated with the transmission of vCJD prions to the Val129 genotype is not an artifact of PrP overexpression. This finding further reinforces the specific biochemical features of vCJD when transmitted to the human-PrP Val129 sequence.
Extrapolation of results from prion transmission studies based on transgenic mice has to be done with caution, especially when human susceptibility to prions is analyzed. However, our results clearly indicate that PrPVal129 individuals are highly resistant to transmission of cattle BSE or BSE passaged in other species. Also, PrPVal129 individuals might be susceptible to infection with human-passaged BSE (vCJD) prions, and the propagated agents might transmit with molecular and neuropathological properties distinguishable from those of type 4 PrPres. Although the resultant type 5 PrPSc shares the same fragment sizes as those of type 2 PrPSc, the 2 PrPSc types can be distinguished by the predominance of the diglycosylated glycoform associated with type 5 PrPSc. Overall, our results indicate that human Val129-PrP polymorphic variant is a strong molecular protector against BSE zoonotic transmission but fails to prevent human-to-human vCJD transmission. Because potential late-onset vCJD cases could appear in the population (49,50) these findings underline the need for continued investigation of all forms of human prion disease.
''Overall, our results indicate that human Val129-PrP polymorphic variant is a strong molecular protector against BSE zoonotic transmission but fails to prevent human-to-human vCJD transmission. Because potential late-onset vCJD cases could appear in the population (49,50) these findings underline the need for continued investigation of all forms of human prion disease.''
THURSDAY, AUGUST 17, 2017
JAVMA NEWS Atypical BSE found in Alabama cow September 01, 2017
MONDAY, AUGUST 21, 2017
Chronic Wasting Disease Prion Strain Emergence and Host Range Expansion
THURSDAY, AUGUST 17, 2017
Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States revisited 2017
''It remains a remote possibility that when older people contract CJD from BSE the resulting phenotype is like sporadic CJD and is distinct from the vCJD phenotype in younger people.''
Volume 2: Science
4. The link between BSE and vCJD
Summary
4.29 The evidence discussed above that vCJD is caused by BSE seems overwhelming. Uncertainties exist about the cause of CJD in farmers, their wives and in several abattoir workers. It seems that farmers at least might be at higher risk than others in the general population. 1 Increased ascertainment (ie, increased identification of cases as a result of greater awareness of the condition) seems unlikely, as other groups exposed to risk, such as butchers and veterinarians, do not appear to have been affected. The CJD in farmers seems to be similar to other sporadic CJD in age of onset, in respect to glycosylation patterns, and in strain-typing in experimental mice. Some farmers are heterozygous for the methionine/valine variant at codon 129, and their lymphoreticular system (LRS) does not contain the high levels of PrPSc found in vCJD. It remains a remote possibility that when older people contract CJD from BSE the resulting phenotype is like sporadic CJD and is distinct from the vCJD phenotype in younger people.
4.30 Estimates of the likely scale of a possible epidemic of vCJD are wide-ranging and the subject of much debate. To know the likely number of cases is very important, not least to enable preparations to be made for the care of victims, as well as to be able to draw up guidelines to reduce the risk of transmission from infected but asymptomatic people. Preliminary results of the study examining tonsil and appendix material for signs of infection were not informative in this regard and full results are awaited. A blood test that would allow the widespread screening of the population by a simple method is still being sought.
BSE INQUIRY
Volume 2: Science
4. The link between BSE and vCJD
Summary
4.29 The evidence discussed above that vCJD is caused by BSE seems overwhelming. Uncertainties exist about the cause of CJD in farmers, their wives and in several abattoir workers. It seems that farmers at least might be at higher risk than others in the general population. 1 Increased ascertainment (ie, increased identification of cases as a result of greater awareness of the condition) seems unlikely, as other groups exposed to risk, such as butchers and veterinarians, do not appear to have been affected. The CJD in farmers seems to be similar to other sporadic CJD in age of onset, in respect to glycosylation patterns, and in strain-typing in experimental mice. Some farmers are heterozygous for the methionine/valine variant at codon 129, and their lymphoreticular system (LRS) does not contain the high levels of PrPSc found in vCJD. It remains a remote possibility that when older people contract CJD from BSE the resulting phenotype is like sporadic CJD and is distinct from the vCJD phenotype in younger people.
4.30 Estimates of the likely scale of a possible epidemic of vCJD are wide-ranging and the subject of much debate. To know the likely number of cases is very important, not least to enable preparations to be made for the care of victims, as well as to be able to draw up guidelines to reduce the risk of transmission from infected but asymptomatic people. Preliminary results of the study examining tonsil and appendix material for signs of infection were not informative in this regard and full results are awaited. A blood test that would allow the widespread screening of the population by a simple method is still being sought.
BSE INQUIRY
PRION 2015 CONFERENCE
O.05: Transmission of prions to primates after extended silent incubation periods: Implications for BSE and scrapie risk assessment in human populations
Emmanuel Comoy, Jacqueline Mikol, Valerie Durand, Sophie Luccantoni, Evelyne Correia, Nathalie Lescoutra, Capucine Dehen, and Jean-Philippe Deslys Atomic Energy Commission; Fontenay-aux-Roses, France
Prion diseases (PD) are the unique neurodegenerative proteinopathies reputed to be transmissible under field conditions since decades. The transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that an animal PD might be zoonotic under appropriate conditions. Contrarily, in the absence of obvious (epidemiological or experimental) elements supporting a transmission or genetic predispositions, PD, like the other proteinopathies, are reputed to occur spontaneously (atpical animal prion strains, sporadic CJD summing 80% of human prion cases). Non-human primate models provided the first evidences supporting the transmissibiity of human prion strains and the zoonotic potential of BSE. Among them, cynomolgus macaques brought major information for BSE risk assessment for human health (Chen, 2014), according to their phylogenetic proximity to humans and extended lifetime. We used this model to assess the zoonotic potential of other animal PD from bovine, ovine and cervid origins even after very long silent incubation periods.
*** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period,
***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold long incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014),
***is the third potentially zoonotic PD (with BSE and L-type BSE),
***thus questioning the origin of human sporadic cases.
We will present an updated panorama of our different transmission studies and discuss the implications of such extended incubation periods on risk assessment of animal PD for human health.
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***thus questioning the origin of human sporadic cases***
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***our findings suggest that possible transmission risk of H-type BSE to sheep and human. Bioassay will be required to determine whether the PMCA products are infectious to these animals.
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PRION 2016 CONFERENCE
Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice.
Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion.
These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.
SPONTANEOUS ATYPICAL BOVINE SPONGIFORM ENCEPHALOPATHY
***Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility.***
ELEPHANT IN THE ROOM $$$
LOOKING FOR CWD IN HUMANS AS nvCJD or as an ATYPICAL CJD, LOOKING IN ALL THE WRONG PLACES $$$
*** These results would seem to suggest that CWD does indeed have zoonotic potential, at least as judged by the compatibility of CWD prions and their human PrPC target. Furthermore, extrapolation from this simple in vitro assay suggests that if zoonotic CWD occurred, it would most likely effect those of the PRNP codon 129-MM genotype and that the PrPres type would be similar to that found in the most common subtype of sCJD (MM1).***
PRION 2017 CONFERENCE
First evidence of intracranial and peroral transmission of Chronic Wasting Disease (CWD) into Cynomolgus macaques: a work in progress
Stefanie Czub1, Walter Schulz-Schaeffer2, Christiane Stahl-Hennig3, Michael Beekes4, Hermann Schaetzl5 and Dirk Motzkus6 1
University of Calgary Faculty of Veterinary Medicine/Canadian Food Inspection Agency; 2Universitatsklinikum des Saarlandes und Medizinische Fakultat der Universitat des Saarlandes; 3 Deutsches Primaten Zentrum/Goettingen; 4 Robert-Koch-Institut Berlin; 5 University of Calgary Faculty of Veterinary Medicine; 6 presently: Boehringer Ingelheim Veterinary Research Center; previously: Deutsches Primaten Zentrum/Goettingen
This is a progress report of a project which started in 2009. 21 cynomolgus macaques were challenged with characterized CWD material from white-tailed deer (WTD) or elk by intracerebral (ic), oral, and skin exposure routes. Additional blood transfusion experiments are supposed to assess the CWD contamination risk of human blood product. Challenge materials originated from symptomatic cervids for ic, skin scarification and partially per oral routes (WTD brain). Challenge material for feeding of muscle derived from preclinical WTD and from preclinical macaques for blood transfusion experiments. We have confirmed that the CWD challenge material contained at least two different CWD agents (brain material) as well as CWD prions in muscle-associated nerves.
Here we present first data on a group of animals either challenged ic with steel wires or per orally and sacrificed with incubation times ranging from 4.5 to 6.9 years at postmortem. Three animals displayed signs of mild clinical disease, including anxiety, apathy, ataxia and/or tremor. In four animals wasting was observed, two of those had confirmed diabetes. All animals have variable signs of prion neuropathology in spinal cords and brains and by supersensitive IHC, reaction was detected in spinal cord segments of all animals. Protein misfolding cyclic amplification (PMCA), real-time quaking-induced conversion (RT-QuiC) and PET-blot assays to further substantiate these findings are on the way, as well as bioassays in bank voles and transgenic mice.
At present, a total of 10 animals are sacrificed and read-outs are ongoing. Preclinical incubation of the remaining macaques covers a range from 6.4 to 7.10 years. Based on the species barrier and an incubation time of > 5 years for BSE in macaques and about 10 years for scrapie in macaques, we expected an onset of clinical disease beyond 6 years post inoculation.
PRION 2017 DECIPHERING NEURODEGENERATIVE DISORDERS
Subject: PRION 2017 CONFERENCE DECIPHERING NEURODEGENERATIVE DISORDERS VIDEO
PRION 2017 CONFERENCE DECIPHERING NEURODEGENERATIVE DISORDERS
PRION 2017 CONFERENCE VIDEO
Chronic Wasting Disease CWD TSE Prion to Humans, who makes that final call, when, or, has it already happened?
TUESDAY, JUNE 13, 2017
PRION 2017 CONFERENCE ABSTRACT First evidence of intracranial and peroral transmission of Chronic Wasting Disease (CWD) into Cynomolgus macaques: a work in progress
Terry S. Singeltary Sr.
