Classical BSE emergence from Nor98/atypical scrapie: Unraveling the shift vs. selection dichotomy in the prion field
Classical BSE emergence from Nor98/atypical scrapie: Unraveling the shift vs. selection dichotomy in the prion field
Sara Canoyra https://orcid.org/0000-0001-6371-8122, Alba Marín-Moreno https://orcid.org/0000-0002-4023-6398, Juan Carlos Espinosa https://orcid.org/0000-0002-6719-9902, +5 , and Juan María Torres https://orcid.org/0000-0003-0443-9232 jmtorres@inia.csic.esAuthors Info & Affiliations
Edited by Byron Caughey, National Institute of Allergy and Infectious Diseases (National Institutes of Health), Hamilton, MT; received January 17, 2025; accepted June 7, 2025 by Editorial Board Member Lila M. Gierasch
July 15, 2025 122 (29) e2501104122
Classical bovine spongiform encephalopathy (c-BSE) is a fatal cattle prion disease transmissible to humans as variant Creutzfeldt–Jakob Disease (vCJD). Understanding how c-BSE emerges is crucial for preventing future outbreaks and protecting public health. Two main hypotheses explain prion adaptation during cross-species transmission: “conformational shift or deformed templating,” where the species barrier forces a change to a different pathological prion protein, and “conformational selection,” where the species barrier filters preexisting conformers. Our results demonstrate that the conformational shift mechanism explains the emergence of c-BSE when Nor98/atypical scrapie (AS) is transmitted to cattle. This is significant because AS, found in sheep and goats worldwide, can convert to c-BSE. Preventing AS from entering the food chain is crucial to reduce c-BSE/vCJD risks. Abstract
Prion diseases can manifest with distinct phenotypes in a single species, a phenomenon known as prion strains. Upon cross-species transmission, alterations in the disease phenotype can occur, interpreted as the emergence of a new strain. Two main and non–mutually exclusive evolutionary hypotheses have been proposed to explain this phenomenon: the “conformational shift” or “deformed templating” and the “conformational selection.” The conformational shift hypothesis proposes that the introduction of a new host prion protein (PrPC) forces a change in the conformation of the pathological prion protein (PrPSc), causing the new prion strain emergence. On the contrary, the conformational selection model postulates that prion isolates are a conglomerate of PrPSc conformations with relative distribution frequencies, wherein the species barrier acts as a filter selecting the one fittest for the new species environment. Previous studies reported the emergence of the classical bovine spongiform encephalopathy agent (c-BSE) upon transmission of Nor98/atypical scrapie (AS) onto a bovine PrP. This study investigates the evolutionary dichotomy of this c-BSE emergence by using prion strain thermostability combined with protein misfolding cyclic amplification to distinguish between both strains. Our results suggest that the conformational shift could be the principal mechanism responsible for the c-BSE emergence. Furthermore, the selection model was dismissed as the key mechanism based on the analysis of an artificial c-BSE and AS mixture. The ability of the AS conformers to shift conformation to a c-BSE one supports the hypothesis that the epidemic c-BSE prion may have originated from the transmission of AS in cattle.
***> 19 Nor98-like cases since the beginning of RSSS
Nor98-like scrapie was confirmed in 1 sheep sampled in June 2023. The most recent case that tested positive for classical scrapie was in one sheep sampled at slaughter in January of FY 2021. This sheep had resided in a flock in Wisconsin, and VS attributed the flock of origin to Arkansas; it was not completely traceable due to lack of identification to flock of origin.
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There have been 491 NVSL confirmed positive animals (474 classical cases - 471 sheep and 3 goats) and 19 Nor98-like cases since the beginning of RSSS. Figure 3 depicts RSSS collection sites in FY 2023.
Six of the seven cases of BSE identified in the United States have been diagnosed as atypical BSE. In most cases, the animals were 10 years of age or older. Two of the six detections of atypical BSE involved animals aged approximately 5 years or older.
USA BSE Testing and Surveillance?
Bottom line, USA is testing so few cows for BSE (<25k tested annually)
BUT, even at those low testing figures, the USA did just confirm another case of BSE just here recently. Feed ban has failed terribly, and CWD is spreading in the USA, at an alarming rate. Recent transmission studies show oral transmission of CWD of Cervid to cattle. Studies also show links of sporadic CJD to BSE, Scrapie, and CWD. It’s a Whole new game of Prion poker now$$$
Wednesday, May 24, 2023
***> WAHIS, WOAH, OIE, United States of America Bovine spongiform encephalopathy Immediate notification
SATURDAY, MAY 20, 2023
***> Tennessee State Veterinarian Alerts Cattle Owners to Disease Detection Mad Cow atypical L-Type BSE
MAY 19, 2023
2 weeks before the announcement of this recent mad cow case in the USA, i submitted this to the APHIS et al;
***> APPRX. 2 weeks before the recent mad cow case was confirmed in the USA, in Tennessee, atypical L-Type BSE, I submitted this to the APHIS et al;
Document APHIS-2023-0027-0001 BSE Singeltary Comment Submission May 2, 2023
''said 'burden' cost, will be a heavy burden to bear, if we fail with Bovine Spongiform Encephalopathy BSE TSE Prion disease, that is why this information collection is so critical''...
Bovine Spongiform Encephalopathy BSE TSE Prion Origin USA?, what if?
Research Project: Pathobiology, Genetics, and Detection of Transmissible Spongiform Encephalopathies Location: Virus and Prion Research
Title: Sheep are susceptible to the agent of TME by intracranial inoculation and have evidence of infectivity in lymphoid tissues
Author item CASSMANN, ERIC - Oak Ridge Institute For Science And Education (ORISE) item MOORE, SARA - Oak Ridge Institute For Science And Education (ORISE) item SMITH, JODI - Iowa State University item Greenlee, Justin
Submitted to: Frontiers in Veterinary Science Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/14/2019 Publication Date: 11/29/2019 Citation: Cassmann, E.D., Moore, S.J., Smith, J.D., Greenlee, J.J. 2019.
Sheep are susceptible to the agent of TME by intracranial inoculation and have evidence of infectivity in lymphoid tissues.
Frontiers in Veterinary Science. 6:430. https://doi.org/10.3389/fvets.2019.00430. DOI: https://doi.org/10.3389/fvets.2019.00430
Interpretive Summary: Prion diseases are protein misfolding diseases that are transmissible between animals. The outcome of prion infection is irreversible brain damage and death. Transmission can occur between animals of the same or different species, however, transmission between different species is usually less efficient due to the species barrier, which results from differences in the amino acid sequence of the prion protein between the donor and recipient species. The present work evaluated whether transmissible mink encephalopathy (TME) can infect sheep. Our results demonstrate that sheep are susceptible to the TME agent and that the TME agent has similar properties to the agent of L-type atypical bovine spongiform encephalopathy (L-BSE). This work supports the ideas that L-BSE is a possible source for TME in mink and that the practice of feeding cattle with neurologic disease to mink should be avoided. This information is important to farmers who raise cattle, sheep, or mink.
Technical Abstract: Transmissible mink encephalopathy (TME) is a food borne prion disease. Epidemiological and experimental evidence suggests similarities between the agent of TME and L-BSE. This experiment demonstrates the susceptibility of four different genotypes of sheep to the agent of TME by intracranial inoculation. The four genotypes of sheep used in this experiment had polymorphisms corresponding to codons 136 and 171 of the prion gene: VV136QQ171, AV136QQ171, AA136QQ171, and AA136QR171. All intracranially inoculated sheep without comorbidities (15/15) developed clinical scrapie and had detectable PrPSc by immunohistochemistry, western blot, and enzyme immunoassay (EIA). The mean incubation periods in TME infected sheep correlated with their relative genotypic susceptibility. There was peripheral distribution of PrPSc in the trigeminal ganglion and neuromuscular spindles; however, unlike classical scrapie and C-BSE in sheep, ovine TME did not accumulate in the lymphoid tissue. To rule out the presence of infectious, but proteinase K susceptible PrPSc, the lymph nodes of two sheep genotypes, VV136QQ171 and AA136QQ171, were bioassayed in transgenic ovinized mice. None of the mice (0/32) inoculated by the intraperitoneal route had detectable PrPSc by EIA. Interestingly, mice intracranially inoculated with RPLN tissue from a VV136QQ171 sheep were EIA positive (3/17) indicating that sheep inoculated with TME harbor infectivity in their lymph nodes. Western blot analysis demonstrated similarities in the migration patterns between ovine TME and the bovine TME inoculum. Overall, these results demonstrate that sheep are susceptible to the agent of TME, and that the tissue distribution of PrPSc in TME infected sheep is distinct from classical scrapie.
Previous work has shown that the Stetsonville, WI outbreak of TME could have been precipitated by feeding mink a downer cow with atypical BSE; therefore, it very well may have originated from a cow with L-BSE. The agent of TME appears to remain stable, and it has a high transmission efficiency after a sequence of interspecies transmission events. Although C-BSE is the archetypal foodborne TSE, our findings indicate that L-BSE and bTME have greater transmission efficiencies in bovinized mice. Previous work has demonstrated that L-BSE also is more virulent than C-BSE in mice expressing the human prion protein [46, 55]. Although the documented incidence of L-BSE is low, the propensity of L-BSE and the TME agent to cross species barriers support the continued monitoring for atypical BSE.
***>This work supports the ideas that L-BSE is a possible source for TME in mink and that the practice of feeding cattle with neurologic disease to mink should be avoided. This information is important to farmers who raise cattle, sheep, or mink.<***
1985
Evidence That Transmissible Mink Encephalopathy Results from Feeding Infected Cattle Over the next 8-10 weeks, approximately 40% of all the adult mink on the farm died from TME.
snip...
The rancher was a ''dead stock'' feeder using mostly (>95%) downer or dead dairy cattle...
Re-USA BSE Surveillance, BSE Testing, BSE Feed Regulation (21 CFR 589.2000), SRMs, and CWD
“Conclusion: These results demonstrate the oral transmission potential of atypical BSE in cattle. Surprisingly, regardless of which atypical type of BSE was used for P1 oral challenge, Prpsc in the P2 animals acquired biochemical characteristics similar to that of Prps in C-BSE, suggesting atypical BSE as a possible origin of C-BSE in UK.”
Abstract for Prion 2023
Title: Transmission of atypical BSE: a possible origin of Classical BSE in cattle
Authors: Sandor Dudas'
1, Samuel James Sharpe', Kristina Santiago-Mateo', Stefanie Czub', Waqas Tahirl,2, *
Affiliation: National and WOAH reference Laboratory for Bovine Spongiform Encephalopathy, Canadian Food inspection Agency, Lethbridge Laboratory, Lethbridge, Canada. ?Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada.
*Corresponding and Presenting Author: waqas.tahir@inspection.gc.ca
Background: Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disease of cattle and is categorized into classical and atypical forms. Classical BSE (C-BSE) is linked to the consumption of BSE contaminated feed whereas atypical BSE is considered to be spontaneous in origin. The potential for oral transmission of atypical BSE is yet to be clearly defined. Aims: To assess the oral transmissibility of atypical BSE (H and L type) in cattle. Should transmission be successful, determine the biochemical characteristics and distribution of Prpso in the challenge cattle.
Material and Methods: For oral transmission, calves were fed with 100 g of either H (n=3) or L BSE (n=3) positive brain material. Two years post challenge, 1 calf from each of the H and L BSE challenge groups exhibited behavioural signs and were euthanized.
Various brain regions of both animals were tested by traditional and novel prion detection methods with inconclusive results. To detect infectivity, brain homogenates from these oral challenge animals (P1) were injected intra-cranially (IC) into steer calves. Upon clinical signs of BSE, 3/4 of IC challenged steer calves were euthanized and tested for Prpsc with ELISA, immunohistochemistry and immunoblot.
Results: After 6 years of incubation, 3/4 animals (2/2 steers IC challenged with brain from P1 L-BSE oral challenge and 1/2 steer IC challenged with brain from P1 H-BSE oral challenge) developed clinical disease. Analysis of these animals revealed high levels of Prpsc in their brains, having biochemical properties similar to that of Prps in C-BSE.
Conclusion: These results demonstrate the oral transmission potential of atypical BSE in cattle. Surprisingly, regardless of which atypical type of BSE was used for P1 oral challenge, Prpsc in the P2 animals acquired biochemical characteristics similar to that of Prps in C-BSE, suggesting atypical BSE as a possible origin of C-BSE in UK.
Presentation Type: Oral Presentation
Funded by: CFIA, Health Canada, Alberta Livestock and Meat Agency, Alberta Prion Research Institute
Grant Number: ALMA/APRI: 201400006, HC 414250
“Conclusion: These results demonstrate the oral transmission potential of atypical BSE in cattle. Surprisingly, regardless of which atypical type of BSE was used for P1 oral challenge, Prpsc in the P2 animals acquired biochemical characteristics similar to that of Prps in C-BSE, suggesting atypical BSE as a possible origin of C-BSE in UK.”
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Molecular phenotype shift after passage of low-type bovine spongiform encephalopathy (L-BSE).
Zoe J. Lambert, M. Heather West Greenlee, Jifeng Bian, Justin J. Greenlee Ames, USA
Aims: The purpose of this study is to compare the molecular phenotypes of L-BSE in wild type cattle and cattle with the E211K polymorphism to samples of other cattle TSEs, such as classical BSE (C-BSE), hightype BSE (H-BSE), and transmissible mink encephalopathy (TME).
Materials and Methods: Two wild type cattle (EE211 PRNP) and one steer with the E211K polymorphism (EK211) were intracranially inoculated with 1 mL of brain homogenate that originated from a 2005 French L-BSE case. Multiple assays were used to compare and differentiate tissues, including enzyme immunoassay, western blot (Sha31, 12B2, SAF84), stability (Sha31), and immunohistochemistry (F99/97).
Results: Approximately 16.6 months post-inoculation, Steer 6 (EK211 L-BSE) developed neurologic signs, including agitation, difficulty eating accompanied by weight loss, head tremor, ataxia, and fasciculations in the forelimbs, and was necropsied. Enzyme immunoassays demonstrated misfolded prion protein in the brainstem (4.0 O.D) but not in peripheral tissues, such as the retropharyngeal lymph node and palatine tonsil. When compared by western blot, the molecular phenotype of the brainstem of Steer 6 (EK211 L-BSE) is higher than that of wildtype cattle inoculated with L-BSE, requiring careful differentiation from C-BSE. Ongoing mouse studies in bovinized mice (K211 and TgBov) will provide data to compare to all other BSE strains available, including L-BSE, C-BSE, H-BSE, E211K H-BSE, and TME.
Conclusions: Further study of L-BSE in EK211 cattle with a higher molecular phenotype in the brainstem may give more insight into the origin of C-BSE.
Funded by: This research was funded in its entirety by congressionally appropriated funds to the United States Department of Agriculture, Agricultural Research Service. The funders of the work did not influence study design, data collection and analysis, decision to publish, or preparation of the manuscript. This research was supported in part by an appointment to the Agricultural Research Service (ARS) Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA). ORISE is managed by ORAU under DOE contract number DE-SC0014664. All opinions expressed in this paper are the author’s and do not necessarily reflect the policies and views of USDA, ARS, DOE, or ORAU/ORISE.
Grant number: DOE contract number DE-SC0014664 Acknowledgements: NA Theme: Animal prion diseases
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PRION 2023 CONTINUED;
The L-type BSE prion is much more virulent in primates and in humanized mice than is the classical BSE prion, which suggests the possibility of zoonotic risk associated with the L-type BSE prion
Consumption of L-BSE–contaminated feed may pose a risk for oral transmission of the disease agent to cattle.
Thus, it is imperative to maintain measures that prevent the entry of tissues from cattle possibly infected with the agent of L-BSE into the food chain.
Atypical L-type bovine spongiform encephalopathy (L-BSE) transmission to cynomolgus macaques, a non-human primate
Fumiko Ono 1, Naomi Tase, Asuka Kurosawa, Akio Hiyaoka, Atsushi Ohyama, Yukio Tezuka, Naomi Wada, Yuko Sato, Minoru Tobiume, Ken'ichi Hagiwara, Yoshio Yamakawa, Keiji Terao, Tetsutaro Sata
Affiliations expand
PMID: 21266763
Abstract
A low molecular weight type of atypical bovine spongiform encephalopathy (L-BSE) was transmitted to two cynomolgus macaques by intracerebral inoculation of a brain homogenate of cattle with atypical BSE detected in Japan. They developed neurological signs and symptoms at 19 or 20 months post-inoculation and were euthanized 6 months after the onset of total paralysis. Both the incubation period and duration of the disease were shorter than those for experimental transmission of classical BSE (C-BSE) into macaques. Although the clinical manifestations, such as tremor, myoclonic jerking, and paralysis, were similar to those induced upon C-BSE transmission, no premonitory symptoms, such as hyperekplexia and depression, were evident. Most of the abnormal prion protein (PrP(Sc)) was confined to the tissues of the central nervous system, as determined by immunohistochemistry and Western blotting. The PrP(Sc) glycoform that accumulated in the monkey brain showed a similar profile to that of L-BSE and consistent with that in the cattle brain used as the inoculant. PrP(Sc) staining in the cerebral cortex showed a diffuse synaptic pattern by immunohistochemistry, whereas it accumulated as fine and coarse granules and/or small plaques in the cerebellar cortex and brain stem. Severe spongiosis spread widely in the cerebral cortex, whereas florid plaques, a hallmark of variant Creutzfeldt-Jakob disease in humans, were observed in macaques inoculated with C-BSE but not in those inoculated with L-BSE.
see full text;
See also;
OIE 2019 atypical BSE
Given that cattle have been successfully infected by the oral route, at least for L-BSE, it is reasonable to conclude that atypical BSE is potentially capable of being recycled in a cattle population if cattle are exposed to contaminated feed. In addition, based on reports of atypical BSE from several countries that have not had C-BSE, it appears likely that atypical BSE would arise as a spontaneous disease in any country, albeit at a very low incidence in old cattle. In the presence of livestock industry practices that would allow it to be recycled in the cattle feed chain, it is likely that some level of exposure and transmission may occur. As a result, since atypical BSE can be reasonably considered to pose a potential background level of risk for any country with cattle, the recycling of both classical and atypical strains in the cattle and broader ruminant populations should be avoided.
Annex 7 (contd) AHG on BSE risk assessment and surveillance/March 2019
34 Scientific Commission/September 2019
3. Atypical BSE
The Group discussed and endorsed with minor revisions an overview of relevant literature on the risk of atypical BSE being recycled in a cattle population and its zoonotic potential that had been prepared ahead of the meeting by one expert from the Group. This overview is provided as Appendix IV and its main conclusions are outlined below. With regard to the risk of recycling of atypical BSE, recently published research confirmed that the L-type BSE prion (a type of atypical BSE prion) may be orally transmitted to calves1 . In light of this evidence, and the likelihood that atypical BSE could arise as a spontaneous disease in any country, albeit at a very low incidence, the Group was of the opinion that it would be reasonable to conclude that atypical BSE is potentially capable of being recycled in a cattle population if cattle were to be exposed to contaminated feed. Therefore, the recycling of atypical strains in cattle and broader ruminant populations should be avoided.
4. Definitions of meat-and-bone meal (MBM) and greaves
Consumption of L-BSE–contaminated feed may pose a risk for oral transmission of the disease agent to cattle.
Thus, it is imperative to maintain measures that prevent the entry of tissues from cattle possibly infected with the agent of L-BSE into the food chain.
''H-TYPE BSE AGENT IS TRANSMISSIBLE BY THE ORONASAL ROUTE''
This study demonstrates that the H-type BSE agent is transmissible by the oronasal route. These results reinforce the need for ongoing surveillance for classical and atypical BSE to minimize the risk of potentially infectious tissues entering the animal or human food chains.
Previous studies have demonstrated that L-BSE can be orally transmitted to cattle (7) and might have caused prion disease in farm-raised minks (6), indicating that L-BSE could naturally affect various animal species. Our findings suggest that L-BSE can also be orally transmitted to macaques. Therefore, current control measures aimed at preventing primary C-BSE in cattle and humans may also need to consider the potential risk of spontaneous L-BSE transmission.
Volume 31, Number 5—May 2025
Dispatch
Administration of L-Type Bovine Spongiform Encephalopathy to Macaques to Evaluate Zoonotic Potential
Morikazu Imamura1Comments to Author , Ken’ichi Hagiwara, Minoru Tobiume, Minako Ohno, Hiromi Iguchi, Hanae Takatsuki, Tsuyoshi Mori, Ryuichiro Atarashi, Hiroaki Shibata, and Fumiko Ono1 Author affiliation: University of Miyazaki, Miyazaki, Japan (M. Imamura, M. Ohno, H. Iguchi, H. Takatsuki, T. Mori, R. Atarashi); National Institute of Infectious Diseases, Tokyo, Japan (K. Hagiwara, M. Tobiume); The Corporation for Production and Research of Laboratory Primates, Tsukuba, Japan (H. Shibata); Okayama University of Science, Imabari, Japan (F. Ono) Cite This Article
Abstract
We administered L-type bovine spongiform encephalopathy prions to macaques to determine their potential for transmission to humans. After 75 months, no clinical symptoms appeared, and prions were undetectable in any tissue by Western blot or immunohistochemistry. Protein misfolding cyclic amplification, however, revealed prions in the nerve and lymphoid tissues.
Worldwide emergence of classical bovine spongiform encephalopathy (C-BSE) is associated with variant Creutzfeldt-Jakob disease in humans (1). Two other naturally occurring BSE variants have been identified, L-type (L-BSE) and H-type. Studies using transgenic mice expressing human normal prion protein (PrPC) (2) and primates (3–5) have demonstrated that L-BSE is more virulent than C-BSE. Although L-BSE is orally transmissible to minks (6), cattle (7), and mouse lemurs (5), transmissibility to cynomolgus macaques, a suitable model for investigating human susceptibility to prions, remains unclear. We orally inoculated cynomolgus macaques with L-BSE prions and explored the presence of abnormal prion proteins (PrPSc) in tissues using protein misfolding cyclic amplification (PMCA) along with Western blot (WB) and immunohistochemistry (IHC). PMCA markedly accelerates prion replication in vitro, and its products retain the biochemical properties and transmissibility of seed prion strains (8).
The Study
Two macaques orally inoculated with L-BSE prions remained asymptomatic and healthy but were euthanized and autopsied at 75 months postinoculation. WB showed no PrPSc accumulation in any tissue (Table), IHC revealed no PrPSc accumulation, hematoxylin and eosin staining revealed no spongiform changes in brain sections, and pathologic examination revealed no abnormalities.
Snip…
Conclusion We noted no detectable evidence of PrPSc by WB or IHC in any tissues of L-BSE orally inoculated macaques. Nevertheless, PMCA successfully amplified PrPres from lymphatic and neural tissues. The PrPres exhibited electrophoretic patterns distinct from those detected by PMCA using L-BSE–affected cattle BH as the seed (Figure 3, panel C), indicating that the PrPSc used as the template for PrPres amplification in orally inoculated macaques did not originate from the bovine L-BSE prions used as inoculum. Instead, PrPSc were newly generated by the conversion of macaque PrPC by bovine L-BSE prions. Our results provide strong evidence that L-BSE can infect macaques via the oral route.
We found no evidence that PrPSc reached the brain in orally inoculated macaques; however, the macaques euthanized 6 years postinoculation might have been in the preclinical period. At low infection levels, lymph nodes play a vital role in prion spread to the central nervous system (11). Therefore, had the macaques been maintained for a longer period, they might have developed prion disease. Retrospective surveillance studies using the appendix and tonsil tissues suggested a considerable number of humans harboring vCJD in a carrier state (12). Thus, we cannot exclude that L-BSE orally inoculated macaques could similarly remain in a potentially infectious state.
The brain of L-BSE intracerebrally inoculated macaque accumulated prions with biochemical properties resembling bovine L-BSE prions (Figure 3, panel C; Appendix Figure 2); however, we observed no PrPSc accumulation in lymphoid tissues by WB or IHC (4). In contrast, macaques orally inoculated with C-BSE prions showed PrPSc accumulation in lymphoid tissues, including the spleen, tonsils, and mesenteric lymph nodes by WB and IHC (13). In our study, L-BSE orally inoculated macaques harbored C-BSE–like prions in their lymphoid and neural tissues. Interspecies transmission of L-BSE prions to ovine PrP transgenic mice can result in a shift toward C-BSE–like properties (14,15). Our data suggest that L-BSE prions may alter biophysical and biochemical properties, depending on interspecies transmission and inoculation route, acquiring traits similar to those of C-BSE prions. This transformation might result from structural changes in the L-BSE prion to C-BSE–like prions and other lymphotropic prions within lymphoid tissues or from the selective propagation of low-level lymphotropic substrains within the L-BSE prion population.
The first limitation of our study is that the oral inoculation experiment involved only 2 macaques and tissues collected at 6 years postinoculation, before disease onset. Consequently, subsequent progression of prion disease symptoms remains speculative. A larger sample size and extended observation periods are required to conclusively establish infection in orally inoculated macaques. Furthermore, we performed no bioassays for PMCA-positive samples, leaving the relationship between PMCA results and infectious titers undefined. Considering that PrPres amplifications from tissues from the orally inoculated macaque tissues required 2 rounds of PMCA, the PrPSc levels in positive tissues might have been extremely low and undetectable in the bioassay.
Previous studies have demonstrated that L-BSE can be orally transmitted to cattle (7) and might have caused prion disease in farm-raised minks (6), indicating that L-BSE could naturally affect various animal species. Our findings suggest that L-BSE can also be orally transmitted to macaques. Therefore, current control measures aimed at preventing primary C-BSE in cattle and humans may also need to consider the potential risk of spontaneous L-BSE transmission.
Dr. Imamura is an associate professor in the Division of Microbiology, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, Miyazaki, Japan. His research interests are focused on elucidating the mechanisms underlying prion formation.
Acknowledgment This study was supported by the Health Labor Sciences Research Grant (H29-Shokuhin-Ippan-004, 20KA1003, and 23KA1004).
References…snip…end
MONDAY, JUNE 09, 2025
The naturally occurring lysine to glutamic acid substitution (E211K in the bovine prion protein) results in short incubation periods for H-type bovine spongioform encephalopathy (BSE), Singeltary Review
THURSDAY, JUNE 5, 2025
World Organisation for Animal Health (WOAH) downgrades UK’s BSE risk rating to negligible, what could go wrong?
Monday, May 22, 2023
BSE TSE Prion MAD COW TESTING IN THE USA COMPARED TO OTHER COUNTRIES?
FRIDAY, JULY 07, 2023
TME, 589.2000 (21 C.F.R. 589.2000), atypical L-BSE, who’s testing MINK for TSE?
posted by Terry S. Singeltary Sr. at
10:50 AM
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