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Mabbott NA. How do PrP Sc Prions Spread between Host Species, and within Hosts? Pathogens 2017; 6:pathogens6040060. [PMID: 29186791 PMCID: PMC5750584 DOI: 10.3390/pathogens6040060] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 11/16/2017] [Accepted: 11/21/2017] [Indexed: 12/22/2022] Open
Abstract
Prion diseases are sub-acute neurodegenerative diseases that affect humans and some domestic and free-ranging animals. Infectious prion agents are considered to comprise solely of abnormally folded isoforms of the cellular prion protein known as PrPSc. Pathology during prion disease is restricted to the central nervous system where it causes extensive neurodegeneration and ultimately leads to the death of the host. The first half of this review provides a thorough account of our understanding of the various ways in which PrPSc prions may spread between individuals within a population, both horizontally and vertically. Many natural prion diseases are acquired peripherally, such as by oral exposure, lesions to skin or mucous membranes, and possibly also via the nasal cavity. Following peripheral exposure, some prions accumulate to high levels within the secondary lymphoid organs as they make their journey from the site of infection to the brain, a process termed neuroinvasion. The replication of PrPSc prions within secondary lymphoid organs is important for their efficient spread to the brain. The second half of this review describes the key tissues, cells and molecules which are involved in the propagation of PrPSc prions from peripheral sites of exposure (such as the lumen of the intestine) to the brain. This section also considers how additional factors such as inflammation and aging might influence prion disease susceptibility.
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Affiliation(s)
- Neil A Mabbott
- The Roslin Institute & Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Easter Bush, Midlothian EH25 9RG, UK
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2
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Adams DB. Prenatal transmission of scrapie in sheep and goats: A case study for veterinary public health. Open Vet J 2016; 6:194-214. [PMID: 27928518 PMCID: PMC5133396 DOI: 10.4314/ovj.v6i3.8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 10/26/2016] [Indexed: 01/11/2023] Open
Abstract
Unsettled knowledge as to whether scrapie transmits prenatally in sheep and goats and transmits by semen and preimplantation embryos has a potential to compromise measures for controlling, preventing and eliminating the disease. The remedy may be analysis according to a systematic review, allowing comprehensive and accessible treatment of evidence and reasoning, clarifying the issue and specifying the uncertainties. Systematic reviews have clearly formulated questions, can identify relevant studies and appraise their quality and can summarise evidence and reasoning with an explicit methodology. The present venture lays a foundation for a possible systematic review and applies three lines of evidence and reasoning to two questions. The first question is whether scrapie transmits prenatally in sheep and goats. It leads to the second question, which concerns the sanitary safety of artificial breeding technologies, and is whether scrapie transmits in sheep and goats by means of semen and washed or unwashed in vivo derived embryos. The three lines of evidence derive from epidemiological, field and clinical studies, experimentation, and causal reasoning, where inferences are made from the body of scientific knowledge and an understanding of animal structure and function. Evidence from epidemiological studies allow a conclusion that scrapie transmits prenatally and that semen and embryos are presumptive hazards for the transmission of scrapie. Evidence from experimentation confirms that semen and washed or unwashed in vivo derived embryos are hazards for the transmission of scrapie. Evidence from causal reasoning, including experience from other prion diseases, shows that mechanisms exist for prenatal transmission and transmission by semen and embryos in both sheep and goats.
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Affiliation(s)
- D B Adams
- 24 Noala Street, Aranda, ACT 2614, Australia
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Konold T, Thorne L, Simmons HA, Hawkins SAC, Simmons MM, González L. Evidence of scrapie transmission to sheep via goat milk. BMC Vet Res 2016; 12:208. [PMID: 27640200 PMCID: PMC5027119 DOI: 10.1186/s12917-016-0807-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 08/19/2016] [Indexed: 11/25/2022] Open
Abstract
Background Previous studies confirmed that classical scrapie can be transmitted via milk in sheep. The current study aimed to investigate whether scrapie can also be transmitted via goat milk using in vivo (new-born lambs fed milk from scrapie-affected goats due to the unavailability of goat kids from guaranteed scrapie-free herds) and in vitro methods (serial protein misfolding cyclic amplification [sPMCA] on milk samples). Results In an initial pilot study, new-born lambs of two different prion protein gene (PRNP) genotypes (six VRQ/VRQ and five ARQ/ARQ) were orally challenged with 5 g brain homogenate from two scrapie-affected goats to determine susceptibility of sheep to goat scrapie. All sheep challenged with goat scrapie brain became infected based on the immunohistochemical detection of disease-associated PrP (PrPsc) in lymphoid tissue, with an ARQ/ARQ sheep being the first to succumb. Subsequent feeding of milk to eight pairs of new-born ARQ/ARQ lambs, with each pair receiving milk from a different scrapie-affected goat, resulted in scrapie in the six pairs that received the largest volume of milk (38–87 litres per lamb), whereas two pairs fed 8–9 litres per lamb, and an environmental control group raised on sheep milk from healthy ewes, did not show evidence of infection when culled at up to 1882 days of age. Infection in those 12 milk recipients occurred regardless of the clinical status, PrPsc distribution, caprine arthritis-encephalitis virus infection status and PRNP polymorphisms at codon 142 (II or IM) of the donor goats, but survival time was influenced by PRNP polymorphisms at codon 141. Serial PMCA applied to a total of 32 milk samples (four each from the eight donor goats collected throughout lactation) detected PrPsc in one sample each from two goats. Conclusions The scrapie agent was present in the milk from infected goats and was able to transmit to susceptible species even at early preclinical stage of infection, when PrPsc was undetectable in the brain of the donor goats. Serial PMCA as a PrPsc detection method to assess the risk of scrapie transmission via milk in goats proved inefficient compared to the bioassay. Electronic supplementary material The online version of this article (doi:10.1186/s12917-016-0807-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Timm Konold
- Animal Sciences Unit, Animal and Plant Health Agency Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK.
| | - Leigh Thorne
- Virology Department, Animal and Plant Health Agency Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Hugh A Simmons
- Animal Sciences Unit, Animal and Plant Health Agency Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Steve A C Hawkins
- Pathology Department, Animal and Plant Health Agency Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Marion M Simmons
- Pathology Department, Animal and Plant Health Agency Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK
| | - Lorenzo González
- Pathology Department, Animal and Plant Health Agency Lasswade, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK
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Jeffrey M, Witz JP, Martin S, Hawkins SAC, Bellworthy SJ, Dexter GE, Thurston L, González L. Dynamics of the natural transmission of bovine spongiform encephalopathy within an intensively managed sheep flock. Vet Res 2015; 46:126. [PMID: 26511838 PMCID: PMC4625529 DOI: 10.1186/s13567-015-0269-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/09/2015] [Indexed: 11/29/2022] Open
Abstract
Sheep are susceptible to the bovine spongiform encephalopathy (BSE) agent and in the UK they may have been exposed to BSE via contaminated meat and bone meal. An experimental sheep flock was established to determine whether ovine BSE could be naturally transmitted under conditions of intensive husbandry. The flock consisted of 113 sheep of different breeds and susceptible PRNP genotypes orally dosed with BSE, 159 sheep subsequently born to them and 125 unchallenged sentinel controls. BSE was confirmed in 104 (92%) orally dosed sheep and natural transmission was recorded for 14 of 79 (18%) lambs born to BSE infected dams, with rates varying according to PRNP genotype. The likelihood of natural BSE transmission was linked to stage of incubation period of the dam: the attack rate for lambs born within 100 days of the death of BSE infected dams was significantly higher (9/22, 41%) than for the rest (5/57, 9%). Within the group of ewes lambing close to death, those rearing infected progeny (n = 8, for 9/12 infected lambs) showed a significantly greater involvement of lymphoid tissues than those rearing non-infected offspring (n = 8, for 0/10 infected lambs). Horizontal transmission to the progeny of non-infected mothers was recorded only once (1/205, 0.5%). This low rate of lateral transmission was attributed, at least partly, to an almost complete absence of infected placentas. We conclude that, although BSE can be naturally transmitted through dam-lamb close contact, the infection in this study flock would not have persisted due to low-efficiency maternal and lateral transmissions.
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Affiliation(s)
- Martin Jeffrey
- Animal and Plant Health Agency (APHA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK.
| | - Janey P Witz
- Animal and Plant Health Agency (APHA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK.
| | - Stuart Martin
- Animal and Plant Health Agency (APHA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK.
| | | | | | | | - Lisa Thurston
- APHA-Weybridge, New Haw, Addlestone, Surrey, KT15 3NB, UK.
| | - Lorenzo González
- Animal and Plant Health Agency (APHA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK.
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Chianini F, Cosseddu GM, Steele P, Hamilton S, Hawthorn J, Síso S, Pang Y, Finlayson J, Eaton SL, Reid HW, Dagleish MP, Di Bari MA, D’Agostino C, Agrimi U, Terry L, Nonno R. Correlation between infectivity and disease associated prion protein in the nervous system and selected edible tissues of naturally affected scrapie sheep. PLoS One 2015; 10:e0122785. [PMID: 25807559 PMCID: PMC4373927 DOI: 10.1371/journal.pone.0122785] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/12/2015] [Indexed: 01/19/2023] Open
Abstract
The transmissible spongiform encephalopathies (TSEs) or prion diseases are a group of fatal neurodegenerative disorders characterised by the accumulation of a pathological form of a host protein known as prion protein (PrP). The validation of abnormal PrP detection techniques is fundamental to allow the use of high-throughput laboratory based tests, avoiding the limitations of bioassays. We used scrapie, a prototype TSE, to examine the relationship between infectivity and laboratory based diagnostic tools. The data may help to optimise strategies to prevent exposure of humans to small ruminant TSE material via the food chain. Abnormal PrP distribution/accumulation was assessed by immunohistochemistry (IHC), Western blot (WB) and ELISA in samples from four animals. In addition, infectivity was detected using a sensitive bank vole bioassay with selected samples from two of the four sheep and protein misfolding cyclic amplification using bank vole brain as substrate (vPMCA) was also carried out in selected samples from one animal. Lymph nodes, oculomotor muscles, sciatic nerve and kidney were positive by IHC, WB and ELISA, although at levels 100-1000 fold lower than the brain, and contained detectable infectivity by bioassay. Tissues not infectious by bioassay were also negative by all laboratory tests including PMCA. Although discrepancies were observed in tissues with very low levels of abnormal PrP, there was an overall good correlation between IHC, WB, ELISA and bioassay results. Most importantly, there was a good correlation between the detection of abnormal PrP in tissues using laboratory tests and the levels of infectivity even when the titre was low. These findings provide useful information for risk modellers and represent a first step toward the validation of laboratory tests used to quantify prion infectivity, which would greatly aid TSE risk assessment policies.
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Affiliation(s)
- Francesca Chianini
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
- * E-mail:
| | - Gian Mario Cosseddu
- Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
| | - Philip Steele
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Scott Hamilton
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Jeremy Hawthorn
- Animal and Plant Health Agency (APHA -Weybridge), New Haw, Addlestone, Surrey, KT15 3NB, United Kingdom
| | - Sílvia Síso
- Animal and Plant Health Agency (APHA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Yvonne Pang
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Jeanie Finlayson
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Samantha L. Eaton
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Hugh W. Reid
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Mark P. Dagleish
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, United Kingdom
| | - Michele Angelo Di Bari
- Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
| | - Claudia D’Agostino
- Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
| | - Umberto Agrimi
- Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
| | - Linda Terry
- Animal and Plant Health Agency (APHA -Weybridge), New Haw, Addlestone, Surrey, KT15 3NB, United Kingdom
| | - Romolo Nonno
- Department of Food Safety and Veterinary Public Health, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy
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Head MW, Yull HM, Törö K, Keller E, Rozsa C, Ironside JW, Kovacs GG. Pathological and biochemical investigation of a woman diagnosed with genetic Creutzfeldt-Jakob disease shortly after parturition. Neuropathol Appl Neurobiol 2014; 41:676-80. [PMID: 25486858 DOI: 10.1111/nan.12204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 12/03/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Mark W Head
- National CJD Research & Surveillance Unit, Bryan Matthews Building, Western General Hospital, Edinburgh, Scotland, UK
| | - Helen M Yull
- National CJD Research & Surveillance Unit, Bryan Matthews Building, Western General Hospital, Edinburgh, Scotland, UK
| | - Klara Törö
- Department of Forensic and Insurance Medicine, Semmelweis University, Budapest, Hungary
| | - Eva Keller
- Department of Forensic and Insurance Medicine, Semmelweis University, Budapest, Hungary
| | - Csilla Rozsa
- Department of Neurology, Jahn Ferenc Delpesti Hospital, Budapest, Hungary
| | - James W Ironside
- National CJD Research & Surveillance Unit, Bryan Matthews Building, Western General Hospital, Edinburgh, Scotland, UK
| | - Gabor G Kovacs
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
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Jeffrey M, Martin S, Chianini F, Eaton S, Dagleish MP, González L. Incidence of infection in Prnp ARR/ARR sheep following experimental inoculation with or natural exposure to classical scrapie. PLoS One 2014; 9:e91026. [PMID: 24614120 PMCID: PMC3948952 DOI: 10.1371/journal.pone.0091026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 02/06/2014] [Indexed: 12/02/2022] Open
Abstract
The prion protein gene (Prnp) is highly influential in determining risk and susceptibility of sheep exposed to classical scrapie. Sheep homozygous for alanine at codon 136 and arginine at codons 154 and 171 (ARR/ARR) of the Prnp gene are historically considered to be highly resistant to classical scrapie, although they form a significant fraction of cases of atypical scrapie. To date, experimental transmission of prions to ARR/ARR sheep has only been achieved with the BSE agent and mostly by the intracerebral route. We summarise here the results of six separate studies, in which 95 sheep of the ARR/ARR genotype were naturally exposed to (n = 18) or experimentally challenged with (n = 77) natural or experimental sources of classical scrapie by the oral, intra-intestinal, subcutaneous or intracerebral routes and allowed to survive for periods of up to 94 months post-infection. Only the intracerebral route resulted in disease and/or amplification of disease associated PrP (PrPd), and only in two of 19 sheep that survived for longer than 36 months. Discriminatory immunohistochemistry and Western blot confirmed the scrapie, non-BSE signature of PrPd in those two sheep. However, the neuropathological phenotype was different from any other scrapie (classical or atypical) or BSE source previously reported in sheep of any Prnp genotype. These studies confirm the widely held view that ARR/ARR sheep are highly resistant to classical scrapie infection, at least within their commercial lifespan. Moreover, within the constraints of the present studies (only two infected sheep), these results do not support the suggestion that atypical scrapie or BSE are generated by adaptation or mutation of classical scrapie in sheep of resistant ARR/ARR genotype.
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Affiliation(s)
- Martin Jeffrey
- Animal Health and Veterinary Laboratories Agency (AHVLA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
- * E-mail:
| | - Stuart Martin
- Animal Health and Veterinary Laboratories Agency (AHVLA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
| | - Francesca Chianini
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
| | - Samantha Eaton
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
| | - Mark P. Dagleish
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
| | - Lorenzo González
- Animal Health and Veterinary Laboratories Agency (AHVLA-Lasswade), Pentlands Science Park, Bush Loan, Penicuik, Midlothian, Scotland, United Kingdom
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Foster JD, Goldmann W, Hunter N. Evidence in sheep for pre-natal transmission of scrapie to lambs from infected mothers. PLoS One 2013; 8:e79433. [PMID: 24260219 PMCID: PMC3832582 DOI: 10.1371/journal.pone.0079433] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 09/19/2013] [Indexed: 01/09/2023] Open
Abstract
Natural scrapie transmission from infected ewes to their lambs is thought to occur by the oral route around the time of birth. However the hypothesis that scrapie transmission can also occur before birth (in utero) is not currently favoured by most researchers. As scrapie is an opportunistic infection with multiple infection routes likely to be functional in sheep, definitive evidence for or against transmission from ewe to her developing fetus has been difficult to achieve. In addition the very early literature on maternal transmission of scrapie in sheep was compromised by lack of knowledge of the role of the PRNP (prion protein) gene in control of susceptibility to scrapie. In this study we experimentally infected pregnant ewes of known PRNP genotype with a distinctive scrapie strain (SSBP/1) and looked for evidence of transmission of SSBP/1 to the offspring. The sheep were from the NPU Cheviot flock, which has endemic natural scrapie from which SSBP/1 can be differentiated on the basis of histology, genetics of disease incidence and strain typing bioassay in mice. We used embryo transfer techniques to allow sheep fetuses of scrapie-susceptible PRNP genotypes to develop in a range of scrapie-resistant and susceptible recipient mothers and challenged the recipients with SSBP/1. Scrapie clinical disease, caused by both natural scrapie and SSBP/1, occurred in the progeny but evidence (including mouse strain typing) of SSBP/1 infection was found only in lambs born to fully susceptible recipient mothers. Progeny were not protected from transmission of natural scrapie or SSBP/1 by washing of embryos to International Embryo Transfer Society standards or by caesarean derivation and complete separation from their birth mothers. Our results strongly suggest that pre-natal (in utero) transmission of scrapie may have occurred in these sheep.
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Affiliation(s)
- James D. Foster
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian, Scotland, United Kingdom
| | - Wilfred Goldmann
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian, Scotland, United Kingdom
| | - Nora Hunter
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian, Scotland, United Kingdom
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Influence of polymorphisms in the prion protein gene on the pathogenesis and neuropathological phenotype of sheep scrapie after oral infection. J Comp Pathol 2013; 150:57-70. [PMID: 24342584 DOI: 10.1016/j.jcpa.2013.10.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 09/06/2013] [Accepted: 10/02/2013] [Indexed: 11/20/2022]
Abstract
The prion protein gene (Prnp) plays a crucial role in the susceptibility of sheep to scrapie in terms of attack rate and/or incubation period. However, the influence of Prnp on the pathogenesis of the disease, specifically the involvement of tissues of the lymphoreticular system (LRS), pathways of neuroinvasion and neuropathological phenotypes, remains controversial. This study reports the onset and progression of disease-associated prion protein (PrP(d)) accumulation in the LRS and nervous tissues of sheep of six different Prnp genotypes infected by oral administration of the same mixed scrapie brain homogenate. Sheep homozygous for glutamine (Q) at codon 171 of PrP, with either valine (V) or alanine (A) at codon 136 (i.e. VRQ/VRQ, VRQ/ARQ and ARQ/ARQ), showed early and consistent PrP(d) accumulation in LRS tissues of the pharynx and gut. In contrast, LRS involvement was minimal, inconsistent and occurred late in the incubation period in sheep heterozygous for arginine (R) at codon 171 (i.e. VRQ/ARR and ARQ/ARR). Despite this difference, all five groups were susceptible to infection and developed clinical disease, albeit with significantly different incubation periods (shortest in VRQ/VRQ and longest in ARQ/ARR sheep). The remaining group of ARR/ARR homozygous sheep did not show evidence of infection at the end of the experiment or at previous predetermined time points. As for LRS tissues, the sites of initial PrP(d) accumulation in the brain were determined immunohistochemically. These were the same in all susceptible sheep (except for ARR/ARR sheep), regardless of their Prnp genotype which, together with an early and consistent accumulation of PrP(d) in circumventricular organs and a late or inconsistent involvement of the enteric and autonomic nervous system and of the spinal cord, suggests neuroinvasion occurring via the blood. The neuropathological phenotype (PrP(d) profile in the central nervous system) of clinically affected sheep was similar in the three V136 carrier groups, but showed some differences in the two A136 homozygous groups, suggesting a codon 136-driven selection of different strains from the mixture contained in the inoculum. ARQ/ARR sheep showed an irregular distribution of brain PrP(d), contrasting with the more widespread distribution of the other four groups. The results indicate that (1) ARQ/ARR sheep are more susceptible to oral scrapie infection than would be predicted from incidence figures in natural disease, (2) amplification and accumulation of PrP(d) in LRS tissues is host genotype dependent, but does not necessarily have a marked effect on the outcome of the infection and (3) the neuropathological phenotype of scrapie is related to the host genotype, but possibly in combination with the infecting source.
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Identical pathogenesis and neuropathological phenotype of scrapie in valine, arginine, glutamine/valine, arginine, glutamine sheep infected experimentally by the oral and conjunctival routes. J Comp Pathol 2013; 150:47-56. [PMID: 24035191 DOI: 10.1016/j.jcpa.2013.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/02/2013] [Accepted: 06/23/2013] [Indexed: 01/06/2023]
Abstract
The pathogenesis of scrapie in sheep after natural or oral exposure to the infectious agent generally involves the early accumulation of disease-associated prion protein (PrP(d)) in the lymphoreticular system (LRS). This phase is followed by neuroinvasion, for which two routes, ascending neural and haematogenous, have been postulated. The present study reports the use of immunohistochemistry to track the tissue progression of PrP(d) deposition in sheep of a single, highly scrapie-susceptible PrP genotype administered by the oral or conjunctival routes. Regardless of the route of infection, the earliest detection of PrP(d) was in gut- and pharynx-associated LRS tissues. Subsequently, the brain became PrP(d) positive simultaneously with other LRS tissues, but before the spinal cord and peripheral nervous tissues of the enteric, parasympathetic and sympathetic systems. The sites of initial PrP(d) accumulation in the brain were the dorsal motor nucleus of the vagus and the hypothalamus and their related circumventricular organs (the area postrema and the median eminence, respectively). These were the same for both routes of infection. Rapid progression to clinical disease was observed in sheep infected orally or conjunctivally, with definite signs of scrapie recorded at around 6 and 8 months after infection, respectively. Longer incubation periods in sheep infected by the conjunctival route were probably due to them receiving a lower dose than those infected orally. Irrespective of the route of infection, clinically affected sheep showed the same pathological phenotype (PrP(d) profile) and PrP(d) distribution throughout the brain. The identical peripheral and central pathogenesis observed in sheep of both groups suggests early dissemination of the infectious agent in the bloodstream and a common neuroinvasion pathway. The late involvement of the enteric and autonomic nervous system supports a haematogenous route of infection to the brain.
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Jeffrey M. Review: Membrane-associated misfolded protein propagation in natural transmissible spongiform encephalopathies (TSEs), synthetic prion diseases and Alzheimer's disease. Neuropathol Appl Neurobiol 2013; 39:196-216. [DOI: 10.1111/nan.12004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 11/06/2012] [Indexed: 12/17/2022]
Affiliation(s)
- M. Jeffrey
- Lasswade Laboratory; Animal Health and Veterinary Laboratories Agency; Penicuik; UK
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12
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Thorne L, Holder T, Ramsay A, Edwards J, Taema MM, Windl O, Maddison BC, Gough KC, Terry LA. In vitro amplification of ovine prions from scrapie-infected sheep from Great Britain reveals distinct patterns of propagation. BMC Vet Res 2012; 8:223. [PMID: 23153009 PMCID: PMC3559253 DOI: 10.1186/1746-6148-8-223] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 10/30/2012] [Indexed: 11/12/2022] Open
Abstract
Background Protein misfolding cyclic amplification (PMCA) is a method that facilitates the detection of prions from many sources of transmissible spongiform encephalopathy (TSE). Sheep scrapie represents a unique diversity of prion disease agents in a range of susceptible PRNP genotypes. In this study PMCA was assessed on a range of Great Britain (GB) sheep scrapie isolates to determine the applicability to veterinary diagnosis of ovine TSE. Results PrPSc amplification by protein misfolding cyclic amplification (PMCA) was assessed as a diagnostic tool for field cases of scrapie. The technique was initially applied to thirty-seven isolates of scrapie from diverse geographical locations around GB, and involved sheep of various breeds and PRNP genotypes. All samples were amplified in either VRQ and/or ARQ PrPC substrate. For PrPSc from sheep with at least one VRQ allele, all samples amplified efficiently in VRQ PrPC but only PrPSc from ARH/VRQ sheep amplified in both substrates. PrPSc from ARQ/ARQ sheep displayed two amplification patterns, one that amplified in both substrates and one that only amplified in ARQ PrPC. These amplification patterns were consistent for a further 14/15 flock/farm mates of these sheep. Furthermore experimental scrapie strains SSBP1, Dawson, CH1641 and MRI were analysed. SSBP1 and Dawson (from VRQ/VRQ sheep) amplified in VRQ but not ARQ substrate. MRI scrapie (from ARQ/ARQ sheep) nor CH1641 did not amplify in ARQ or VRQ substrate; these strains required an enhanced PMCA method incorporating polyadenylic acid (poly(A)) to achieve amplification. Conclusions PrPsc from 52 classical scrapie GB field isolates amplified in VRQ or ARQ or both substrates and supports the use of PMCA as a rapid assay for the detection of a wide range of ovine classical scrapie infections involving multiple PRNP genotypes and scrapie strains.
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Affiliation(s)
- Leigh Thorne
- Animal Health Veterinary Laboratories Agency (AHVLA), New Haw, Addlestone, Surrey, UK
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González L, Jeffrey M, Dagleish MP, Goldmann W, Sisó S, Eaton SL, Martin S, Finlayson J, Stewart P, Steele P, Pang Y, Hamilton S, Reid HW, Chianini F. Susceptibility to scrapie and disease phenotype in sheep: cross-PRNP genotype experimental transmissions with natural sources. Vet Res 2012; 43:55. [PMID: 22748008 PMCID: PMC3460791 DOI: 10.1186/1297-9716-43-55] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 06/14/2012] [Indexed: 11/10/2022] Open
Abstract
It has long been established that the sheep Prnp genotype influences the susceptibility to scrapie, and some studies suggest that it can also determine several aspects of the disease phenotype. Other studies, however, indicate that the source of infection may also play a role in such phenotype. To address this question an experiment was set up in which either of two different natural scrapie sources, AAS from AA136 Suffolk and VVC from VV136 Cheviot sheep, were inoculated into AA136, VA136 and VV136 sheep recipients (n = 52). The immunohistochemical (IHC) profile of disease-associated PrP (PrPd) accumulation in the brain of recipient sheep was highly consistent upon codon 136 homologous and semi-homologous transmission, but could be either similar to or different from those of the inoculum donors. In contrast, the IHC profiles were highly variable upon heterologous transmission (VVC to AA136 and AAS to VV136). Furthermore, sheep of the same Prnp genotype could exhibit different survival times and PrPd profiles depending on the source of infection, and a correlation was observed between IHC and Western blot profiles. It was found that additional polymorphisms at codons 112 or 141 of AA136 recipients resulted in a delayed appearance of clinical disease or even in protection from infection. The results of this study strongly suggest that the scrapie phenotype in sheep results from a complex interaction between source, donor and recipient factors, and that the Prnp genotype of the recipient sheep does not explain the variability observed upon codon 136 heterologous transmissions, arguing for other genetic factors to be involved.
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Affiliation(s)
- Lorenzo González
- Animal Health and Veterinary Laboratories Agency, Pentlands Science Park, Bush Loan, Midlothian, EH26 0PZ, United Kingdom.
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