Transmission of Chronic Wasting Disease Identifies a Prion Strain Causing Cachexia and Heart Infection in Hamsters
Richard A. Bessen1*, Cameron J. Robinson2, Davis M. Seelig3, Christopher P. Watschke1, Diana Lowe1, Harold Shearin1, Scott Martinka1, Alex M. Babcock2
1 Department of Immunology and Infectious Diseases, Montana State University, Bozeman, Montana, United States of America,
2 Department of Psychology, Montana State University, Bozeman, Montana, United States of America,
3 Department of Microbiology, Immunology, and Pathology, Colorado State University, Ft. Collins, Colorado, United States of America
Chronic wasting disease (CWD) is an emerging prion disease of free-ranging and captive cervids in North America. In this study we established a rodent model for CWD in Syrian golden hamsters that resemble key features of the disease in cervids including cachexia and infection of cardiac muscle. Following one to three serial passages of CWD from white-tailed deer into transgenic mice expressing the hamster prion protein gene, CWD was subsequently passaged into Syrian golden hamsters. In one passage line there were preclinical changes in locomotor activity and a loss of body mass prior to onset of subtle neurological symptoms around 340 days. The clinical symptoms included a prominent wasting disease, similar to cachexia, with a prolonged duration. Other features of CWD in hamsters that were similar to cervid CWD included the brain distribution of the disease-specific isoform of the prion protein, PrPSc, prion infection of the central and peripheral neuroendocrine system, and PrPSc deposition in cardiac muscle. There was also prominent PrPSc deposition in the nasal mucosa on the edge of the olfactory sensory epithelium with the lumen of the nasal airway that could have implications for CWD shedding into nasal secretions and disease transmission. Since the mechanism of wasting disease in prion diseases is unknown this hamster CWD model could provide a means to investigate the physiological basis of cachexia, which we propose is due to a prion-induced endocrinopathy. This prion disease phenotype has not been described in hamsters and we designate it as the ‘wasting’ or WST strain of hamster CWD.
A prominent feature of CWD in deer is a progressive loss of body mass and adiposity over a period of weeks to months . This observation is not unique among prion diseases since a wasting phenotype is also found in sheep and goats with scrapie . Despite interspecies transmission of CWD and scrapie to rodents, a similar progressive wasting disease has not been described in SGH except in the terminal stages of disease . In the current study, we describe a progressive loss of body mass and cachexia over several weeks in SGH with CWD that resulted in an average of >50% weight loss at the time of animal sacrifice when hamsters were still active, but not yet moribund. We have termed this progressive disease in SGH the ‘wasting’ phenotype or WST strain of CWD since overt symptoms of neurological symptoms were not prominent for most of the disease phase. The loss of body mass in WST CWD in SGH was distinct from that reported for other natural prion diseases adapted to SGH including transmissible mink encephalopathy (e.g., HY and DY strains) , , , scrapie (e.g., 263K, 22AH, Me7H strains) , , CWD , , bovine spongiform encephalopathy , , and Creutzfeldt-Jakob disease  in which changes in body mass were not evident until the late phases of clinical disease or were not described. Changes in body weight have been reported in sheep scrapie that was adapted to SGH, but in these cases there is a preclinical obesity that is characterized by a >25% increase in body mass for the 22CH and 139H scrapie agent strains –, . The cellular basis for either prion-induced cachexia or obesity is not completely understood, but an analysis of energy homeostasis in 139H scrapie in SGH revealed a preclinical hyperphagia, non-fasted hyperinsulinemia with hyperglycemia, and fasted hyperleptinemia that is consistent with an anabolic syndrome that had similarities to type II diabetes mellitus , . A similar analysis was performed for HY TME in SGH that exhibit a loss of body mass during the late clinical phase of disease and these animals have a different profile that includes hypersecretion of glucagon, increased fasted ß-ketones, fasted hypoglycemia, and suppressed, non-fasted leptin . It was proposed that in HY TME the SGH had a catabolic syndrome and we would predict that WST CWD in SGH would exhibit a more severe catabolic syndrome than found in HY TME since the weight loss was longer in duration and more pronounced. Additional factors that may have also contributed to the severe loss of body mass in WST CWD in SGH include the increased locomotor activity (e.g., distance traveled, average speed, number of rotations) that was first observed at 43 weeks postinfection and hypophagia that was first recorded at 48 weeks postinfection. These preceded the average time of animal sacrifice at 54 weeks postinfection. This data is suggestive of an increased energy expenditure without an increase in energy intake for several weeks. These prion-induced changes resulted in an imbalance between caloric expenditure and intake and could have exacerbated the loss of body mass.
The observed changes in open field behavior in WST CWD-infected SGH, which proceeded the appearance of clinical signs, are consistent with previous studies that reported increased locomotor activity in rodent prion infections –. The present study confirms and extends these findings by demonstrating preclinical hyperactivity in the CWD SGH model. Increased locomotor activity can represent a hyper-reactivity to novel stimuli or impaired novelty-induced exploration. The detailed analysis of open field behavior in the present study revealed no difference in the thigmotaxis between control and infected SGH subjects, which is indicative of normal emotionality . In contrast, WST CWD in SGH resulted in increased rotational behavior that has not been previously reported. The direction (clockwise vs counterclockwise) of increased rotational behavior observed in experimental hamsters was not consistent and may represent differences in the intra-hemispheric deposition of PrPSc in brain structures following CWD infection. Although speculative, the wide spread distribution of PrPSc in structures including the cerebellar white matter, thalamus, hippocampus and substantia nigra can be link to the observed changes in behavior. In addition, abnormal behavior and motor deficits in prion disease models have been associated with changes in the hypothalamo-pituitary-adrenal (HPA) axis . Prion-induced changes in the HPA are also consistent with the wasting syndrome observed in WST CWD in SGH and in cervids with CWD. Irrespective of the origin or mechanism(s), early behavioral markers of prion infection are of epidemiological importance.
Prion-induced endocrinopathies have been proposed to be the primary cause of either obesity or cachexia observed in natural and experimental prion diseases , . These can be explained by prion infection of the HPA that results in altered secretion of neuroendocrine hormones or pituitary hormones , . These in turn regulate endocrine gland function that can affect body mass and adiposity. Alternatively, prions may directly infect peripheral endocrine glands and alter hormone secretion. Support for these mechanisms can be found in CWD in cervids, sheep scrapie, BSE in cattle, and some human prion diseases in which prion infection has been found in hypothalamic nuclei, the pituitary gland, pancreas, and/or adrenal gland , , , , , –. In the current study PrPSc deposition was also found in several hypothalamic nuclei, the pancreas, and adrenal gland in WST CWD in SGH. In both the adrenal gland and pancreas, PrPSc deposition was associated with markers for neural structures within these tissues suggesting that prion-induced changes in neural control of these endocrine glands could alter hormone secretion. For example, localization of PrPSc to PGP 9.5-positive structures in the medulla of the adrenal gland could result in a prion effect on sympathetic regulation of adrenaline and noradrenaline, and previous studies have demonstrated increased levels of catecholamines in blood of scrapie infected mice and hamsters , , and humans with fatal familial insomnia . Similarly, in the pancreas of WST CWD in SGH, PrPSc deposition was associated with synaptophysin-positive structures in the Islet of Langerhans, which is the region containing the hormone producing cells. In several prion diseases infection of the Islet of Langerhans is reported as well as altered levels of pancreatic hormones in serum including insulin and glucagons suggesting that these endocrinopathies are associated with prion infection of the endocrine system –. In other studies, elevated serum levels of leptin, which acts on the hypothalamus to suppress appetite, was described in 139H scrapie in SGH despite evidence of hyperphagia and obesity . These studies suggest that the dysregulation of the endocrine system in prion diseases is complex and could be due to the targeting of prion infection to multiple sites in both the central and peripheral endocrine system. To understand the cellular basis of wasting disease in CWD additional studies are needed to investigate metabolite and hormone serum levels involved in endocrine function and we propose that the WST CWD in SGH can provide a model to investigate the basis of prion-induced cachexia.
Transmission of CWD from white-tailed deer, mule deer, and elk to TgMo-sghPrP and SGH was undertaken in a previous study , and our transmission data of CWD from white-tailed deer into the same founder line of TgMo-sghPrP and outbred SGH produced some different findings. Raymond et al  demonstrate a very long incubation period on interspecies transmission of white-tailed deer CWD into TgMo-sghPrP (632±73 days with 4 of 9 mice affected, but 8 of 9 mice were PrPSc-positive in brain) that shortened to 272±62 days on second serial passage, and 212±32 and 237±13 days on third serial passage. Our data resulted in a 100% attack rate and a shorter incubation period on interspecies passage (417±23 days) that stabilized to 198±3 days on second serial passage, and did not significantly shorten on third serial passage (189±5 and 198±3 days). Our transmission data on CWD from TgMo-sghPrP into SGH was also distinct from the previous study  in which the mean incubation periods ranged from 408 to 462 days, while in the current study they consistently resulted in mean incubation periods ranging from 322 to 379 days on first and second serial passage into SGH. In passage line B we did observe a longer incubation period (477±15 days) that was consistent with the studies by Raymond et al , but this occurred after inoculation of brain material from a CWD infected TgMo-sghPrP that had an incubation period that was 157 days while in the earlier study the inocula was from CWD infected TgMo-sghPrP that had incubation periods significantly longer (>270 days). Therefore, the serial passage history of CWD in TgMo-sghPrP was different between these two studies despite a similar incubation period in a subset of SGH. A comparison of the findings from these two studies may suggest that distinct strains of CWD were isolated upon interspecies passage into TgMo-sghPrP and serial passage into SGH, but these conclusions cannot be reached based solely on incubation periods. More extensive analysis of the biological and biochemical phenotypes of hamster adapted CWD isolates would be necessary in order to identify distinct strains of CWD in SGH. Despite intensive efforts to identify CWD strains using TgMo-cervidPrP, which is a more appropriate model for CWD strain identification, only two distinct strains of CWD have been identified and these are strongly influenced by a normal polymorphism in the cervid Prnp .
The WST CWD strain in SGH has several similarities to CWD in cervids including a progressive wasting disease, a similar brain distribution of PrPSc, and targeting of prion infection to the neuroendocrine portion of the adrenal gland and pancreas. Additionally, in natural prion diseases of humans and animals, infection of cardiac muscle has only been described in elk and white-tailed deer with CWD . In WST CWD of SGH, PrPSc was also prominent in heart by western blot and cardiac muscle by immunofluoresence. These findings provide another parallel between CWD infection of cervids and WST SGH. Prion infectivity has been described in muscle from CWD deer  and PrPSc can also be enriched from the tongue of deer and elk infected with CWD . Although low levels of PrPSc were also described in heart of SGH infected with 263K scrapie and BSE adapted to SGH , , the levels described in WST CWD appear to be moderately high since more PrPSc was present in heart than in tongue. Previous studies demonstrate that PrPSc is not detected in heart while the tongue has higher levels of prion infectivity than other muscle types in 263K scrapie infected SGH . Prion protein deposition in cardiac tissue has also been described in red deer that were experimentally infected with CWD . Other observations such as altered locomotor activity and the distinct distribution of PrPSc in the olfactory sensory epithelium in WST CWD of SGH have not been directly compared to cervids with CWD in order to determine whether parallel findings are maintained. An advantage of the WST CWD strain in SGH over other rodent models of CWD could be its usefulness in determining the mechanism of prion-induced wasting disease since this key phenotype is maintained for CWD between the deer host and the WST CWD hamster model.
Citation: Bessen RA, Robinson CJ, Seelig DM, Watschke CP, Lowe D, et al. (2011) Transmission of Chronic Wasting Disease Identifies a Prion Strain Causing Cachexia and Heart Infection in Hamsters. PLoS ONE 6(12): e28026. doi:10.1371/journal.pone.0028026
Editor: Andrew Francis Hill, University of Melbourne, Australia
Received: August 25, 2011; Accepted: October 30, 2011; Published: December 12, 2011
Copyright: © 2011 Bessen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by Public Health Service grants R01 AI055043 and P20 RR020185 from the National Institutes of Health, by the National Research Initiative of the United States Department of Agriculture grant 2006-35201-16626, and The Murphy Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
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40,000 human heart valves a year from BSE herds
Sun, 3 Sep 2000.
Unpublished Inquiry documents obtained by CJD activist Terry S. Singeltary Sr. of Bacliff, Texas
Opinion (webmaster): Below are some shocking documents. Here is a British company preparing 40,000 heart valves a year from bovine pericardium, primarily for export, and they are not required to source this material from BSE-free herds even in peak epidemic years. It is amazing to watch health "authorities" grovelling on their bellies to wring petty concessions from middle management at obscure little companies. The main worry is not the practise of using 800 potentially infected cows a week for human heart transplant material but that the press or recipients will get wind of it, hurting business. BSE wasn't the problem, it was awkward queries from importing countries like the US. The cows are stunned using brain penetration -- can't do anything about the chunks of bovine brain blasted into the circulatory system, it's the norm. Can't use younger lower-risk animals either, patch would not be big enough. It is fascinating to see the British government worrying about, but doing nothing, with pigs with BSE 10 years ago. While scrapie was long used as an excuse for continuing with human use of BSE-tainted material, little sheep material was used medically. Bovine transplants, vaccines, insulin doeses, etc. are far more dangerous than dietary material as injections, and are done on a very wide scale. So scrapie was never a valid analogy to BSE, as MAFF knew full well. The British government deferred to the manufacturer's rep for an opinion on how contaminated pericardium might be, just as this appeared showing that this tissue is extremely dangerous:
CJD in a patient who received homograft [was it really?] tissue for tympanic membrane closure.
Eur Arch Otorhinolaryngol 1990;247(4):199-201
Tange RA, Troost D, Limburg M
We report the case history of a 54-year-old man who developed a fatal neurological disorder 4 years after a successful tympanoplasty with homograft pericardium... COMMERCIAL IN CONFIDENCE
snip...see full text ;
Friday, March 25, 2011
Detection of Prion Protein in Urine-Derived Injectable Fertility Products by a Targeted Proteomic Approach
Sunday, May 1, 2011
W.H.O. T.S.E. PRION Blood products and related biologicals May 2011
DATA ON 2ND CWD STRAIN
Wednesday, September 08, 2010CWD PRION CONGRESS SEPTEMBER 8-11 2010
Saturday, November 12, 2011
Human Prion Disease and Relative Risk Associated with Chronic Wasting Disease
Fri, 22 Sep 2006 09:05:59 -0500
Monday, June 27, 2011
Zoonotic Potential of CWD: Experimental Transmissions to Non-Human Primates
EFSA Journal 2011
The European Response to BSE: A Success Story
This is an interesting editorial about the Mad Cow Disease debacle, and it's ramifications that will continue to play out for decades to come ;
Monday, October 10, 2011
EFSA Journal 2011
The European Response to BSE: A Success Story
EFSA and the European Centre for Disease Prevention and Control (ECDC) recently delivered a scientific opinion on any possible epidemiological or molecular association between TSEs in animals and humans (EFSA Panel on Biological Hazards (BIOHAZ) and ECDC, 2011). This opinion confirmed Classical BSE prions as the only TSE agents demonstrated to be zoonotic so far but the possibility that a small proportion of human cases so far classified as "sporadic" CJD are of zoonotic origin could not be excluded. Moreover, transmission experiments to non-human primates suggest that some TSE agents in addition to Classical BSE prions in cattle (namely L-type Atypical BSE, Classical BSE in sheep, transmissible mink encephalopathy (TME) and chronic wasting disease (CWD) agents) might have zoonotic potential.
see follow-up here about North America BSE Mad Cow TSE prion risk factors, and the ever emerging strains of Transmissible Spongiform Encephalopathy in many species here in the USA, including humans ;
Saturday, June 25, 2011
Transmissibility of BSE-L and Cattle-Adapted TME Prion Strain to Cynomolgus Macaque
"BSE-L in North America may have existed for decades"
Thursday, June 23, 2011
Experimental H-type bovine spongiform encephalopathy characterized by plaques and glial- and stellate-type prion protein deposits
And last but not least, similarities of PrPres between Htype BSE and human prion diseases like CJD or GSS have been put forward , as well as between L-type BSE and CJD . These findings raise questions about the origin and inter species transmission of these prion diseases that were discovered through the BSE active surveillance.
full text 18 pages ;
please see full text ;
R.I.P. MOM DECEMBER 14, 1997 HEIDENHAIN VARIANT OF CREUTZFELDT JAKOB DISEASE