Multiorgan Detection and Characterization of Protease-Resistant Prion Protein in a Case of Variant CJD Examined in the United St
Posted Jan 28 2010 8:26am
PLoS One. 2010; 5(1): e8765. Published online 2010 January 19. doi: 10.1371/journal.pone.0008765. PMCID: PMC2808239
Copyright Notari 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.
Multiorgan Detection and Characterization of Protease-Resistant Prion Protein in a Case of Variant CJD Examined in the United States
Silvio Notari,#1 Francisco J. Moleres,#1 Stephen B. Hunter,2 Ermias D. Belay,3 Lawrence B. Schonberger,3 Ignazio Cali,1 Piero Parchi,4 Wun-Ju Shieh,3 Paul Brown,5 Sherif Zaki,3 Wen-Quan Zou,1 and Pierluigi Gambetti1* 1Institute of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America 2Department of Pathology and Laboratory Medicine, Emory University Hospital, Atlanta, Georgia, United States of America 3National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Center for Disease Control and Prevention, Atlanta, Georgia, United States of America 4Dipartimento di Scienze Neurologiche, Universita' di Bologna, Italy 5CEA/DSV/iMETI/SEPIA, France Delia Goletti, Editor National Institute for Infectious Diseases L. Spallanzani, Italy #Contributed equally. * E-mail: email@example.com Conceived and designed the experiments: SN FJM PG. Performed the experiments: SN FJM IC. Analyzed the data: SN FJM PB WQZ PG. Contributed reagents/materials/analysis tools: SBH WJS SZ PG. Wrote the paper: SN FJM SBH EDB LBS IC PP WJS PB SZ WQZ PG. Received October 19, 2009; Accepted December 18, 2009.
Background Variant Creutzfeldt–Jakob disease (vCJD) is a prion disease thought to be acquired by the consumption of prion-contaminated beef products. To date, over 200 cases have been identified around the world, but mainly in the United Kingdom. Three cases have been identified in the United States; however, these subjects were likely exposed to prion infection elsewhere. Here we report on the first of these subjects.
Methodology/Principal Findings Neuropathological and genetic examinations were carried out using standard procedures. We assessed the presence and characteristics of protease-resistant prion protein (PrPres) in brain and 23 other organs and tissues using immunoblots performed directly on total homogenate or following sodium phosphotungstate precipitation to increase PrPres detectability. The brain showed a lack of typical spongiform degeneration and had large plaques, likely stemming from the extensive neuronal loss caused by the long duration (32 months) of the disease. The PrPres found in the brain had the typical characteristics of the PrPres present in vCJD. In addition to the brain and other organs known to be prion positive in vCJD, such as the lymphoreticular system, pituitary and adrenal glands, and gastrointestinal tract, PrPres was also detected for the first time in the dura mater, liver, pancreas, kidney, ovary, uterus, and skin.
Conclusions/Significance Our results indicate that the number of organs affected in vCJD is greater than previously realized and further underscore the risk of iatrogenic transmission in vCJD.
The oral route of prion infection in vCJD raised the possibility that tissues and organs, beside the central nervous system (CNS), might also be affected. To date, PrPres has been reported in several tissues and organs outside the CNS of vCJD patients (Table 1) [14–19, P. Brown, unpublished data].
Although the amount of PrPres in non-neural tissues is small compared to that in the brain, the risk posed by the spread of even small amounts of PrPres has been underscored by the iatrogenic transmission of vCJD from blood donors in the preclinical phase of the disease .
We examined the main characteristics and tissue distribution of PrPres in a case of vCJD, in which the disease was most likely acquired in the UK but which is officially referred to as an American case because illness onset occurred in the US . In an extensive autopsy examination, sodium phosphotungstate (NaPTA) precipitation, a highly sensitive method of PrPres detection [14,22], was used to establish the presence and estimate the relative amounts of PrPres in several organs and tissues made available to the National Prion Disease Pathology Surveillance Center (NPDPSC).
Results Clinical History Clinical data on the present patient have been reported in detail . Briefly, the patient lived in Britain until the age of 13 and immigrated to the US in 1992. In early November 2001, at the age of 22 years, the patient was evaluated for depression, emotional instability and memory loss, followed one month later by involuntary movements, gait disturbances and incontinence. During the ensuing three months, the patient’s motor and cognitive deficits worsened, and confusion, hallucination, dysarthria, bradykinesia, and spasticity also occurred. The diagnosis of vCJD was made following brain magnetic resonance imaging and confirmed by immunoblot and immunohistochemistry of tonsil tissue. She received an experimental treatment with quinacrine for 3 months, but showed only minimal and transitory improvement. The patient died in June 2004, 32 months after the clinical onset.
Discussion Our study confirms the diagnosis of vCJD in the present case, based on the characteristics of the PrPres and the methionine homozygosity at codon 129 of the PrP gene, the last feature being invariably present in vCJD . However, we also observed two unusual features in this case. The first is the long disease duration of 32 months, which is more than twice the 14 month mean duration of the British cases of vCJD . However, cases of up to 40 months duration after the diseases onset have been reported [3,33]. The second unusual feature is the absence of typical spongiform degeneration which likely stemmed from the long duration of the disease. The long disease duration likely led to extensive loss of neurons, in which most of the vacuoles are formed, with ensuing astroglial scar .
As previously reported , the BSE exposure most likely occurred between the early eighties, when the BSE epidemic emerged in the UK, and 1992, when the patient immigrated to the US. This assumption is consistent with an incubation period of 9 to 21 years, which correlates well with the medium incubation period of 17 years estimated for the UK cases of vCJD . The brain PrPres of the present case displayed the glycoform ratio and electrophoretic mobility characteristic of the PrPres associated with vCJD . One exception is the cerebellum where the monoglycosylated and unglycosylated PrPres isoform migrated slightly faster than the PrPres from other brain regions and resolved in three bands. The variation in PrPres electrophoretic characteristics between the cerebellum and the cerebral cortex is not surprising for it has also been observed in sCJD . Yet to our knowledge it has never been reported in vCJD. Finally, contrary to previous reports , PrPres type 1 did not co-occur with type 2. This discrepancy might stem from our rigorous PrP digestion with PK and from the use of different antibodies, an approach that rules out the possibility that partially cleaved fragments derived by the incomplete digestion of PrPSc be misinterpreted as the type 1 fragment [30,37].
The major finding of the present study is the demonstration that PrPres is present in a number of non-CNS tissues and organs which previous studies had reported as free of PrPres (Table 1 and 2) [14– 19, P. Brown, unpublished data]. These tissues include the dura mater, skin, liver, kidney, pancreas, descending colon, uterus and ovary (Table 2 and Fig. 3). The use of NaPTA, along with the long disease duration, may both have contributed to the undisputed detection of PrPres in these organs in this case. The glycoform ratio of the brain PrPres was not retained in every peripheral organ examined (Fig. 4). In the pituitary gland and the skin the diglycosylated and monoglycosylated PrPres isoforms were about equally represented thus the diglycosylated isoform was not dominant. On the other hand, electrophoretic mobility appeared to match that of the brain. Variations in the glycoform ratio could be assessed only on the TH because the glycoform ratio, as well the electrophoretic mobility, is affected by NaPTA enrichment .
The presence of prion in the human dura mater is not surprising because sCJD has been transmitted following transplantation of dura obtained from sCJD-affected cases . However, to our knowledge this is the first immunoblot demonstration of PrPres in the dura mater in any prion disease. The detection of relatively large amounts of PrPres in the dura mater raises the possibility of contamination with brain tissue at autopsy. Although this possibility cannot be completely ruled out, extensive rinses in PBS were performed before homogenization in some experiments without observing a reduction in the amount of the PrPres detected.
Prion infectivity of kidney and liver has been demonstrated by bioassay in other human prion diseases , and PrPres has been observed in the kidney of scrapie infected sheep . The presence of PrPres has also been reported in kidney, liver and pancreas of scrapie infected mice in association with lymphofollicular proliferation . This last finding is relevant to the present case in which multiple lymphocytic infiltrates with follicular pattern were present in the kidney. However, contrary to this report, we observed no significant inflammatory reaction in any of the other tissues which contained PrPres. A puzzling finding of our study is the presence of PrPres albeit in small amounts in the kidney but not in the urinary bladder. This apparent discrepancy is relevant to the recent demonstrations of prion infectivity in urine
of animals carrying experimental or naturally occurring prion diseases [42–46]. It would indicate that prion infectivity in urine is acquired from the kidney while the urinary bladder acts as a bystander. However the amount of PrPres we observed in the kidney was minimal, and might have not been sufficient to infect the urine and to propagate to the bladder in detectable amounts. Indeed we failed to demonstrate PrPres in the urine in the present case even after hundred-fold urine concentration (data not shown). Obviously more studies are needed to clarify this issue. The present study also demonstrates for the first time the presence of PrPres in the skin in a human prion disease. Previously, PrPres has been detected in the skin from animals with experimental or naturally occurring scrapie  as well as in the antler velvet of elk affected by CWD .
Furthermore, it is remarkable that we observed PrPres in the uterus and the ovary, a finding which implicates the reproductive system, thereby raising the possibility of maternal transmission of vCJD. Vertical transmissibility of prion infection has been demonstrated in transgenic mice infected with BSE . Related literature on human prion diseases is very scanty. Pregnancy completed to delivery has been reported in sCJD, iatrogenic CJD and vCJD [50,51]; however, transmission to the progeny has not been examined in detail or confirmed in any of these cases. The first detailed determination of PrPC and PrPres in the reproductive and gestational tissues from a sCJD patient has been carried out only recently . Although this study failed to detect PrPres, remarkably it showed that, in uterine tissue obtained at biopsy, most of the PK-sensitive PrP is truncated at the N-terminus and matches the C-terminal PrPC fragment C1 which is generated during normal PrPC metabolism . Similarly, in the present case we observed that the C1-like fragment was largely predominant over the full-length PrPC in the uterus, and it was easily digested by PK but it was present along with a significant amount of characteristic vCJD PrPres (Fig. 4). Since the Nterminus of the PrPres type 2 associated with vCJD is at residues 92–99, the uterine PrPres must have formed from the full length PrPC rather than from C1, the N-terminus of which is at residues 111–112 [31,52]. These findings raise the question of the origin of the PrPres found in the uterus, a question that is currently unanswered. A similar question may be raised for the urine, in
which although the prion infectivity has been demonstrated in animals by bioassay [42–46], the only detected form of PrP under normal condition in animals and humans, is a fragment matching the C1 [53, 54, Notari et al., unpublished data].
All these considerations notwithstanding, the widespread presence of PrPres in visceral organs that we observed in the present case further reinforces the concerns over iatrogenic transmission of vCJD. These concerns are already compelling given the multiple reports of vCJD transmission by blood transfusion.