Atypical prion proteins and IBNC in cattle DEFRA project code SE1796 FOIA Final report
Atypical prion proteins and IBNC in cattle DEFRA project code SE1796 FOIA Final report
Executive Summary
Studies of Bovine Spongiform Encephalopathy (BSE), carried out in the UK, showed it to be a single strain of prion disease based on histopathological (Simmons et al., 1996) and transmission data (Bruce et al., 1992 ). First reported in the 1980s (Wells et al., 1987) there appears to have been little change in the characteristics of the disease throughout the epidemic and BSE maintains a distinct molecular profile even following cross species transmission. However, during surveillance programmes in Europe and in North America two other distinct isolates of bovine prion disease have come to light, H and L type, so-called to reflect their unique molecular profiles (Yamakawa et al., 2003; Biacabe et al., 2004).
Reports were also emerging of atypical forms of scrapie that were distinct from classical scrapie isolates and were less easily recognised by the then current diagnostic tests (Benestad et al., 2003; Buschman et al., 2004). This led to concerns that cattle could also harbour a prion disease that was not detected by the current diagnostic tests for BSE. Importantly, approximately 15-20% of the clinical cases submitted for investigation were indeed negative and this proportion of negative cattle did not appear to vary despite increasing awareness of BSE clinical signs by the farming and veterinary community. While there maybe other explanations for this discrepancy (McGill et al., 1993), another underlying undiagnosed prion disease of cattle distinct from classical BSE could not be ruled out.
The study reported here investigated a small number of these BSE negative clinical cases by using more sensitive and modified diagnostic tests for abnormal PrP.
The majority of the cases that we studied were negative by all the tests employed and based on this observation we conclude that there was not a simultaneous epidemic of another form of bovine prion disease. However, we observed a number of classical cases that were missed prior to the advent of sensitive and rapid diagnostic tests and this provides an estimate of the number of cattle that were mis-diagnosed before 2000. In addition, we observed a few rare cases where the diagnostic tests were not in agreement and these cases were investigated further. One of these unusual samples emerged as a case of idiopathic bovine neuronal chromatolysis (IBNC).
During the study we also reported the first H-type BSE case in the UK (Terry et al., 2007).
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Scientific Objectives as prescribed in the project:
All of the objectives have been met and are described in detail below. Three annexes accompany this report, one with the figures for the results below and two papers for submission to peer-reviewed journals.
Objective 1:
To determine the variation of PK sensitivity of bovine PrPc from uninfected cattle brains and compare with bovine PrPsc from classical cases of BSE in order to set thresholds for negative, weak and strong positive values in commercially available rapid diagnostic tests.
Objective 2:
Determine whether there are a greater proportion of bovine brain samples positive for the rapid diagnostic tests (hereby called reactors) in the clinically-suspect, negative subset of cattle than in healthy negative cattle. (True positives will be determined on the basis of evaluation by IHC but should be strongly positive in both the rapid diagnostic tests).
Objective 3:
Determine whether the phenotypic and molecular characteristics of PrP from cattle identified in 2 are distinct from normal PrPc and from bovine PrPsc normally associated with classical BSE.
Studies of Bovine Spongiform Encephalopathy (BSE), carried out in the UK, showed it to be a single strain of prion disease based on histopathological (Simmons et al., 1996) and transmission data (Bruce et al., 1992). First reported in the 1980s (Wells et al., 1987) there appears to have been little change in the these characteristics of the disease throughout the epidemic; BSE also appear to maintain a distinct molecular profile in cattle and even when experimentally (or naturally) transmitted to other species such as humans and cats. However, during surveillance programmes in Europe, Japan and in North America, two other distinct isolates of bovine prion disease have come to light, H and L type, so-called to reflect their unique molecular profiles (Yamakawa et al., 2003; Biacabe et al., 2004).
In the late 1990’s, a novel prion disease was discovered in sheep (Benestad et al., 2003; Buschman et al., 2004); this Nor98 or atypical scrapie is widespread in Europe but had previously been missed by histopathological or immunohistological examination. This led to concerns that cattle could also harbour a prion disease that, unlike H- and L-type BSE, was not detected by the current diagnostic tests for BSE. Importantly, approximately 15-20% of the clinical cases submitted for investigation were indeed negative and this proportion of negative cattle did not appear to vary despite increasing awareness of BSE clinical signs by the farming and veterinary community. While there maybe other explanations for this discrepancy (McGill et al., 1993), another underlying undiagnosed prion disease of cattle distinct from classical BSE could not be ruled out.
The study reported here investigated a small number of these BSE negative clinical cases by using more sensitive and modified diagnostic tests for abnormal PrP. The majority of the cases that we studied were negative by all the tests employed and based on this observation we conclude that there was not a simultaneous epidemic of another form of bovine prion disease. However, we observed a number of cases of BSE in this “BSE negative” sub-set that were missed prior to the advent of more sensitive and rapid diagnostic tests and this provides an estimate of the number of cattle that were mis-diagnosed before 2000. In addition, we observed a few rare cases where the diagnostic tests were not in agreement and these cases were investigated further. One of these unusual samples emerged as a case of idiopathic bovine neuronal chromatolysis (IBNC) (Jeffrey & Wilesmith, 1992; 1996; Jeffrey et al., 2009).
During the study we also reported the first H-type BSE case in the UK (Terry et al., 2007).
Materials and Methods
Tissue samples.
Test samples: Frozen brain stem from 501 bovine BSE suspects with neurological signs, a) that were negative at the level of the obex for vacuolation by standard histopathological techniques from years 1991-1999 and b) by IHC and diagnostic Bio-Rad PlateliaTM from 2000 onwards. These tissues have been stored at the VLA at –80oC since submission.
Negative controls: Frozen brain stem from 90 cattle investigated as part of the active surveillance programme. These samples were submitted in 2006 to LGC for rapid testing by Bio-Rad TeSeE diagnostic ELISA and were negative. These samples were stored at –80oC prior to testing and were stored for a maximum of 36 months and therefore considerably less time than all experimental samples under investigation.
Cattle with suppurative encephalitis: 10 additional cattle samples were retrieved from the VLA Archive that were negative for BSE but showed signs of suppurative encephalitis and inflammation (lymphocyte cuffing and gliosis). These signs were consistent with listeria infection.
Tests for disease-associated PrP
IDEXX BSE Herdchek BSE antigen test kit
All samples were assayed using the IDEXX Herdchek Bovine Spongiform Encephalopathy (BSE) Antigen Test Kit, EIA according to the manufacturer’s instructions and without modification. Briefly, brains were homogenised in the buffer provided by the manufacturer and diluted prior to adding to the seprion (polyanion) coated multiwell plate and incubated prior to washing. The samples were then treated with a conditioning buffer to expose the antigen epitopes. PrPsc was detected by PrP specific antibodies conjugated to horseradish peroxidase and visualised with TMB substrate. Samples were read using a microtitre plate reader (Victor-Perkin-Elmer). The method has no Proteinase K digestion step and has only a mild trypsin treatment that is not required for specificity but aids in the epitope exposure step. The normal curve of negative control samples is provided by the manufacturer and shows the diagnostic cut off value is set higher than most negative controls. The amount of brain added to a single well is approximately 20 mg.
Diagnostic Bio-Rad TeSeE EIA
Sample extraction and detection was carried out according to the manufacturer’s instructions for the Bio-Rad TeSeE BSE ELISA. Briefly brain samples were homogenised in buffer provided by the manufacturer and then treated for 10 mins with Proteinase K at 37oC . The PK concentration is not provided by the manufacturer so we refer to it as 4 ul/ml which is the quantity of stock PK to final solution directed by Bio-Rad. A comparison with sigma PK indicated that the concentration is approximately 40 ug/ml. The samples were then precipitated and concentrated by centrifugation. Pellets were reconstituted and diluted in the buffers provided by the manufacturer. The PrPsc was then detected by a sandwich ELISA provided by the manufacturer. Details of the antibodies are not provided. Samples are read using a microtitre plate as above. Cut off values for the ELISA are calculated using the mean of four negative control ODs. The manufacturers indicate that a value of 0.14 should be added to the negative control mean and samples equal to or greater than this value should be further analysed. The amount of brain added to a single well is approximately 65 mg.
BioRad TeSeE EIA with reduced PK digestion (0.3 Bio-Rad TeSeE ELISA)
The PrPsc associated with atypical scrapie is believed to be less PK resistant than classical scrapie (Everest et al., 2006). In order to investigate whether an atypical form of BSE in cattle exists biochemically similar to atypical scrapie a modified version of the Bio-Rad TeSeE protocol, using sub-diagnostic levels of Proteinase K (0.3ul/ml), was used. This quantity of PK was arrived at by titration of PK and digestion of PrPc from 47 cattle brains negative for TSEs.
The Bio-Rad TeSeE BSE diagnostic test was used as directed by the manufacturer with the addition of DNAse prior to the Proteinase K (0.3 ul/ml PK) treatment and Pefabloc was added alongside the kit PK stopping solution. The PK dilution for these assays was prepared from a Sigma stock solution and 0.3 units/ml was the equivalent activity as 0.3 ul/ml of Biorad PK.
Bio-Rad TeSeE Western Blot
Sample extraction was carried out according to the manufacturer’s instructions (Bio-Rad TeSeE Western Blot) with several modifications. In brief, brain tissue was ribolysed to give 20 % (w/v) homogenate and subsequently incubated with DNAse. The samples were then digested with 0.3, 1, 4 or 20 units/ml PK (Sigma; where units/ml is an in-house nomenclature and 0.3 units/ml is equivalent to 0.3 µl of the Bio-Rad test PK in terms of activity as compared using the TAME test -Pierce) and the reaction stopped with Pefabloc. Following precipitation and centrifugation at 15,000 g for 7 minutes, in accordance with the Bio-Rad TeSeE Western blot protocol, the pellets were re-suspended in Laemmli sample buffer.
For analysis, the supernatants were heated at 100oC for 5 minutes, loaded on a 12% Criterion XT Bis-tris SDS gel (Bio-Rad) and subjected to electrophoresis in XT-MOPS running buffer (Bio-Rad) at 200 V for 50 minutes. Proteins were transferred to a PVDF membrane (Bio-Rad) at 115 V, 60 min using Tris/CAPS transfer buffer (Bio-Rad).
Blots to be evaluated using the Sha31 (Bio-Rad) antibody were incubated for one hour with the blocking solution provided by the manufacturers; and antibodies SAF84 (aa 175-180), P4 (aa 89-104) and FH11 (aa 55-65) using a 5% milk powder in PBS supplemented with Tween 20 (PBST). The membranes were incubated for one hour with the primary antibody and then with goat anti-mouse IgG antibody conjugated to horseradish peroxidase (Bio-Rad) prior to visualization by chemiluminescence (ECL; Amersham).
Immunohistochemical analysis
Formalin-fixed, paraffin wax-embedded tissue blocks were sectioned at 4mm, collected onto frosted charged slides (GmbH) and melted on at 60°C overnight to improve adhesion. Sections were de-waxed in xylene and alcohol and washing in water. They were subsequently put into 98% formic acid (Merck) for 30 minutes, washed in running tap water for 15 minutes and then fully immersed into citrate buffer (200mM trisodium citrate dehydrate (Sigma), 30mM citric acid (Sigma), pH 6.1) prior to being autoclaved for 30 minutes at 121°C. Endogenous peroxidase activity was quenched using 3% hydrogen peroxide (Sigma) and the sections immersed in purified water and stored at 4°C overnight. After warming to room temperature, non-specific antibody binding sites were blocked using normal goat serum (Vector Laboratories) for 20 minutes. Rat monoclonal anti-PrP R145 (VLA) was diluted to 2mg/ml and applied for one hour at ambient (19°C-24°C) temperature. Biotinylated rabbit-anti-mouse IgG (Vector Laboratories) was diluted appropriately and applied for 30 minutes at ambient temperature. Elite ABC (Vector Laboratories) was prepared according to the manufacturers’ directions and applied for 20 minutes at ambient temperature. Sections were washed between each stage using 5mM tris buffered saline supplemented with Tween-20 (5mM tris, 0.85% NaCl, 0.05% tween-20 (all from Sigma), pH 7.6). Diaminobenzidine tablets (Sigma) were prepared in McIlvanes buffer (200mM disodium hydrogen orthophosphate, 100mM citric acid (both from Sigma), pH 6.4) and applied for 10 minutes at ambient temperature. Sections were counterstained in Mayer’s haematoxylin and “blued” in running tap water, before being dehydrated through three changes each of absolute alcohol and xylene for three minutes each and finally mounted in DPX (Sigma).
Definition of terms
Disease associated isoforms of PrP may be distinguished from normal PrP by its increased resistance to Proteinase digestion in immunoblotting or ELISA tests (PrPres), binding to polyanions or labelling with PrP specific antibodies in fixed and treated paraffin-embedded section (PrPd). Included within the operational definition of PrPd are all those detection systems that do not use Proteinase K digestion. The correlation between prion infectivity and PrPres or PrPd is inexact, and infectivity has been dissociated from PrPres or PrPd in several experiments, putatively this is because only a fraction of abnormal PrP isoforms are infectious. We will therefore use operational definitions for detected abnormal PrP forms and PrPsc for the hypothetical infectious sub-population of PrP isoforms detected by bioassay.
Results
Brains from cattle previously diagnosed as negative for BSE based on histopathological examination were investigated in this study for evidence of unusual prion diseases. The majority of the cattle investigated were submitted to the VLA as BSE suspect during the years 1997-2005 and were reported to have clinical signs similar to BSE. We applied a combination of modified and previously unused diagnostic tests to this subgroup of cattle including lower concentrations of PK for protein digestion, tests that do not use PK for PrPsc detection and standard Western blot (WB) procedures with Mabs reactive with different regions of the PrP glycoprotein. A flow chart detailing the sequence for the investigation of potential unusual prion diseases of cattle are shown in Figure 1.
1) Determination of the lowest PK concentration that digests PrPc from brains of cattle
The minimum concentration of PK required for the elimination of PrPc in the majority of non-exposed control cattle samples, resulting in a negative value in the Bio-Rad TeSeE ELISA, was determined. PK titrations were performed on BSE positive and negative control reference material (CRM) and subsequently on 47 individual confirmed negative brainstems. The brainstems had previously tested negative with the diagnostic Bio-Rad TeSeE ELISA by LGC and were obtained from active surveillance and therefore unlikely to have had clinical signs of disease. An amount of 0.3 µl/ml PK was selected for use in the adapted Bio-Rad TeSeE ELISA (0.3 Bio-Rad) (Table 1).
2) Determination of threshold values for the IDEXX HerdChek and 0.3 modified Bio-Rad rapid tests
The diagnostic tests have cut-off values that are set by the manufacturers. For the 0.3 Bio-Rad ELISA new cut-off values were determined to take account of the modifications. While no modifications were made to the IDEXX HerdChek assay cut-off values were calculated using the same test samples for consistency. 90 confirmed BSE negative brainstems were assayed and threshold values calculated as 3 standard deviations above the mean (Table 2). Threshold values of 0.166 Absorbance Units (AU) and 0.137 AU were set for the 0.3 Bio-Rad TeSeE and IDEXX Herdchek EIAs respectively. A single confirmed negative sample gave a value above the IDEXX threshold limit (0.240AU) on first assay. However, when repeated this sample was negative (0.016AU).
3) Results of assays applied to the test BSE cattle population
The assays described above and mapped in Figure 1 were then applied to the brains from 501 clinically suspect cattle. Following analysis the cattle were divided into five groups and these are described below. The results are summarised in Table 3.
Group1: Confirmed negative diagnosis of clinically suspect cattle
Brainstems from 501 cattle submitted to the VLA for BSE diagnosis between the years 1991 and 2005 that were subsequently diagnosed as negative by the tests used at time of slaughter, were assayed using the IDEXX and 0.3 Bio-Rad immunoassays for detection of abnormal PrP. 436 (87%) were negative by both tests. All of the samples submitted after 1999 were confirmed negative (see below) (Figure 8). By these criteria we were unable to detect abnormal PrP in the brainstems of these cattle and this subset of clinically suspect cattle is unlikely to harbour a prion disease. However, we were unable to test other areas of the brain from these cattle and PrPsc distribution patterns distinct from classical BSE cannot be ruled out. In addition to the 501 brainstems we also tested 191 cerebella by the same methods, all of which were negative by standard tests.
Group 2: Confirmed positive for BSE by all diagnostic tests
Sixty five samples remained that were positive in either the IDEXX or the 0.3 Bio-Rad assays or in both of these tests. Of these, 40 were positive by both tests (modified as above) and following retesting were positive using diagnostic concentrations of PK for the Bio-Rad TeSeE (figure 2). Immunohistochemical evaluation of abnormal PrP in the obex demonstrated normal distribution of PrPsc deposits similar to those observed for classical BSE (Figure 8).
To confirm that the PK resistant glycoproteins of abnormal PrP resembled the molecular profile of classical BSE, all 40 cases were immunoblotted using SHa31 MAb (figure 3). In all cases a signature 3 glycoprotein banding pattern was observed with relative mass and glycoprotein ratios indistinguishable from classical BSE. These animals ranged in age from 5 years to 12 years, with a mean age of 6 years, 10 months. All 40 animals were female and comprised 32 Friesians, 2 Holsteins, 2 Herefords, 1 Limousin/Friesian Cross, 2 Holstein/Friesian Cross and 1 Simmental.
The 40 confirmed positive samples were from cattle slaughtered between the years 1997 and 1999. We tested a total of 285 from this period and this represents 14.0% of the clinical suspects that were confirmed negative for BSE at this time. If this is representative of the entire clinical suspect unconfirmed cattle (total 2,426) during this period (1997-1999 inclusive) a total of 340 BSE positive cattle would have been missed. This under-diagnosis is likely to be a result of the diagnostic tests applied at the time. Up until the year 2000, all BSE cases were diagnosed by detection of vacuolation and gliosis in the obex. It is clear that this method is not 100% sensitive for prion diseases either because not all cases present with vacuolation or that vacuolation is a late onset phenomenon during clinical disease (Arnold et al., 2007). Our data showed that there were no additional cases of under-diagnosis after more sensitive diagnostic tests were introduced in 2000. During the years 1997-1999, a total of 12,171 clinical cases were submitted for BSE diagnosis of which 9,745 (80.1%) were confirmed positive with an estimated 2.8% of the total suspects submitted under-diagnosed by our calculations.
Assuming no other factors influenced the levels of correct diagnosis and that the numbers estimated for 1997 to 1999 were a true representation of the potential under-diagnosis of the entire epidemic up until 1999, then the total number of missed cases positive for BSE could have been in the region of 5,500.
A draft version of this manuscript has been prepared.
Group 3: Confirmed positive for BSE by all rapid diagnostic tests but negative by IHC
2 of the 501 negative subset brainstem tested were positive by standard biochemical, diagnostic tests (Table 4) but abnormal PrP deposits were not observed in the obex when evaluated by IHC (Figure 8). This is clearly an unusual finding and both cases were rigorously audited prior to further investigation to determine that the sample for biochemistry was identical to the paraffin-embedded sample. As far as can be determined no errors in sampling and dispatch occurred for these two samples. Further DNA profiling and matching frozen sample to histology processed sample would confirm this. There was insufficient sample to perform any further analysis on one case, but the other case was further investigated using the modified TeSeE Western blot protocol described above – at the diagnostic standard PK concentration of 4 µl/ml for PrPsc digestion. Western blotting of abnormal PrP from this sample confirmed the ELISA data with intense labelling of PK resistant PrP using the PrP-specific antibodies Sha31 and SAF84 (Figure 4a and 4b). The glycoprofile and molecular mass of the PrP bands were indistinguishable from classical BSE A band was labelled strongly with FH11 Mab (that recognises an N terminal PrP epitope) and is therefore likely to represent undigested PrP (Figure 4c). In addition, at 4 µl/ml PK, strong reactivity is also observed with the P4 mAb (Figure 4d). Molecular comparison of this case with classical BSE and with scrapie – using different levels of PK, different dilutions of positive sample and different PrP-specific antibodies, indicates that there is no discernible difference of the test sample with classical BSE. Both cases were extensively followed up by IHC using Mabs to different regions of the PrP molecule but were negative in all cases (data not shown).
Why the PrPsc could not be detected by IHC is unclear. Further analysis by transmission to rodent models of prion disease may shed further light on the characteristics of this sample. Indeed, murine models of prion disease have been reported where PrPsc cannot be detected in the brains but these studies confirmed the lack of PrPsc by all assays including Western Blot.
Group 4: IDEXX Herdchek positive, 0.3 Bio-Rad negative, IHC positive.
Two brainstem samples (98/00819; 98/02316) were positive by the IDEXX Herdchek EIA (Table 5) but Bio-Rad test negative even following PK digestion at sub-optimal concentrations. Both of these samples demonstrated abnormal PrP deposition in the obex by IHC evaluation (Figure 8). Western blot analysis of PK resistant PrP glycoprotein from sample 98/2316 indicated that low amounts of PrPres could be detected using Sha31 and SAF84 Mabs. From these blots and taking into account the low levels of PrPres detected the banding patterns appeared indistinguishable from classical BSE (Figure 5a and 5b). No further sample was available for 98/00819.
The sample contained very low levels of PrPres as shown by the WB data and this is likely to be the reason for lack of signal in the Bio-Rad ELISA. At these levels of abnormal PrP we are at the threshold of detection. The IDEXX HerdChek assay has consistently shown a higher analytical sensitivity for classical scrapie in our hands than the Bio-Rad assays. The values for the IDEXX HerdChek were in the region of 0.15-0.88 and these values are much lower than any of the other samples we have tested in this study. These data suggest that the IDEXX assay is more analytically sensitive than the Bio-Rad TeSeE for BSE.
However, there are alternative explanations for the discordance in test results. The Bio-Rad TeSeE ELISA detects PrPres with Mabs that detect 2 regions of the molecule. Any changes in PrP sequence in the region of Mab binding could alter analytical sensitivity. Therefore the bovine PrP open reading frame from 98/02316 was compared with that of two classical BSE samples, all three samples were 6:6 with respect to the octapeptide repeat. The only mutation seen in this unusual sample was at codon 78 and this is a “silent” mutation in that it does not affect the PrP protein sequence (glutamine, Q78). The Western blot results suggest that the PK cleavage sites of sample 98/02316 were not different from classical cases of BSE. Therefore we conclude that PrPres concentration in this sample was low, as indicated by the control BSE positive brain homogenate, when diluted to a level of 1/250, still producing bands of a far greater density than the test sample when assayed neat.
Group 5: Diagnostic Bio-Rad and IDEXX negative, IHC negative but 0.3 Bio-Rad positive
Twenty-one of the clinical suspect brainstems tested by 0.3 Bio-Rad modified protocol had OD values above the calculated cut off point (range 0.166 to 0.857) (Figure 6) but were IDEXX Herdchek negative and IHC negative (figure 8). The samples were also diagnostic Bio-Rad TeSeE negative and the cattle, all female, ranged in age from 3 years to 11.5 years. They comprised Friesian, Friesian/Holsten, Hereford Cross, Aberdeen Angus Cross, Simmental Cross and Limousin Cross breeds. These samples, where sufficient tissue was available, were analysed, for the presence of partially PK resistant PrP, using the Bio-Rad Western blot protocol with digestion carried out at 20 and 0.3 µl/ml of PK and detected using the SHa31 Mab. Following digestion of the samples with 20 µl/ml PK the samples were shown to be negative for the characteristic PrPsc banding patterns when compared to three individual BSE-negative samples and a classical BSE positive sample (Fig 7a). However, faint bands were observed at approximately 16 and 25 KDa for 4 of the samples (T5, T8-T10) but this faint banding is consistent with partially digested PrPc but could also be a result of variable amounts of protein loaded per lane. At 0.3 µl/ml PK, banding is observed for all test samples, with banding consistent with partially digested PrPC, as also observed for the three known BSE-negative samples. In contrast, the classical BSE-positive sample gave a distinct banding pattern, different from that observed for the BSE-negative samples (Fig.7b). Consistent with the above results samples T5 and T8-T10 demonstrated increased intensity of labelling that could result from an up-regulation or increase in PrPc and could also account for the high signals in the modified ELISA.
Variable banding intensity between lanes may also be a result of inconsistent loading of amounts of protein per lane. However, our previous experience of testing protein concentrations PRIOR to PK digestion in the individual samples showed that they were very consistent to within <5% of the total amount. In addition, although we add pefabloc to stop PK digestion it is also likely that there is variation in the PK digestion amongst samples. Both variables could account for the differences in intensities between lanes. However, we cannot exclude the possibilitity that a PK sensitive variant of abnormal PrP is present as demonstrated by Barron et al 2007 who also demonstrated a 22 KDa band following sub optimal PK digestion. The samples were further investigated as below. Encephalitis may up regulate PrPc One explanation for high values in the immunoassay following digestion with suboptimal concentrations of PK could be high levels of PrPc in the sample. Increased levels of PrPc may occur as a result of up-regulation of PrPc on tissue resident cells or from the influx of inflammatory cells into the site following infection. Differential diagnoses were available for 9 of the 21 animals and nine had confirmed encephalitic lesions and inflammation. Further to this observation we therefore analysed brainstems from 10 BSE negative cattle (but also clinical suspects) by both modified rapid tests that had confirmed encephalitis. The brainstems from 9 encephalitis cattle were negative by both the 0.3 Bio-Rad TeSeE and IDEXX assays. The brainstem from 1 animal was positive by the 0.3 Bio-Rad assay but negative by the IDEXX EIA. The result from this sample is similar to the 21 observed above in group 5. It is unclear therefore whether the high levels of PrP are a result of concurrent infection as there is not a 100% correlation. However, PrPc is more susceptible to endogenous proteases and a low signal could be partly explained by inappropriate handling of the tissue at post-mortem. Loss of PrP detection following retesting of group 5 samples. When all 21 samples were re-analysed from a fresh piece of tissue from the archive (likely to have been frozen and thawed by the archive staff) only one retested as positive (figure 6). Further analysis of this sample (sample number 99/00514) by Western blot has not shown any bands suggesting the presence of an atypical form of prion protein. Any PK sensitive PrP, whether PrPc or unusual prion disease-associated PrP, is likely to be affected by tissue handling techniques including freezing, thawing and the amount of time in storage. This could explain loss of signal. These samples may also represent a small number of outliers in the negative population. This is still higher than we would expect given that only 1/90 negative control samples were outliers in the original testing. Identification of Idiopathic Brainstem Neuronal Chromatolysis (IBNC) in group 5 samples One of the 21 samples identified in group 5 was shown to have IBNC following histological investigation (03/00002) (figure 8). Concurrently, we investigated the PrP distribution in known cases of IBNC (Jeffrey et al 2008; “Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?” BMC Vet Res. 2008 Sep 30;4:38. The IHC and histology profile of this case was very similar to that of the known IBNC cases. Investigation of the distribution and molecular characteristics of PrP from known IBNC See also: Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle? Jeffrey M, Perez BB, Martin S, Terry L, González L. BMC Vet Res. 2008 Sep 30;4:38 Further investigations demonstrated that 57% the assays performed on the confirmed IBNC samples, using the 0.3 Bio-Rad TeSeE assay (n=42), gave values above those of the test kit control and also the BSE negative brain pool control. Half brains from six IBNC affected animals were retrieved from the TSE archive alongside the brainstem from a seventh animal. The cortex, brainstem, cerebellum and midbrain from these brains were sub-sampled and the adapted Bio-Rad TeSeE EIA, IDEXX Herdchek and Western Blot protocols applied to these tissues, in order to determine whether they could represent a form of atypical BSE. These samples had previously been found to be negative using the commercial Bio-Rad EIA and re-testing using this assay and the IDEXX Herdchek assay confirmed their negative status. When assayed using the adapted Bio-Rad protocol at 0.3µl/ml PK, 24/42 (57%) of the sample assays performed gave values above those of the test kit control and also the BSE negative brain pool control. Values above twice that of the calculated cut-off levels were found for each case but not for each brain site No PrPres was detected when Western blotting these samples at either 20 or 4µl/ml PK but a signal was detected on the gels when blotted at the 0.12 and 0.3µl/ml PK levels. At 0.12µl/ml PK the IBNC samples were indistinguishable from the negative controls but at the 0.3µl/ml level more PrPres was detected in the IBNC cases than in the controls with each of the antibodies tested (SHA31, F99, SAF84 and P4). Illustrations of the F99 blot are shown in the paper. Other data not shown. These data suggest that IBNC affected cattle abnormally express or accumulate PrP in brain and that the abnormal PrP is not strongly resistant to protease digestion. The results suggest that either the range of prion diseases is still wider than previously thought or that abnormalities of prion protein expression may be associated with brain lesions unconnected with prion disorders. Biochemical and transmission studies are planned in order to investigate further (under SE2014). First case of H-type BSE identified in GB During the course of this study, 1/5 frozen brainstem from bovine BSE cases when immunoblotted using the Bio-Rad TeSeE Western blot with antibodies P4, L42, 6H4, Sha31 and SAF84, was found to have a PrP profile indistinguishable from French H-type BSE. This sample was the first case of H-type BSE to be identified in GB. It was a fallen 13-year-old Galloway cow, first tested and confirmed as a case of BSE in November 2005. Due to autolysis its brain was unsuitable for further characterisation by IHC. Its age and reported absence of clinical signs are consistent with other cases of H-type BSE. When blotting the samples, mAbs Sha31 and 6H4 revealed, in this sample, an unglycosylated band with relative mobility less than BSE, and mAb P4, labelled the sample more strongly than the BSE samples hence supporting the observed similarities with the French H-type sample. Additionally, this study revealed in both this unusual sample and the French H-type a lower molecular weight band with relative mobility of between 6 and 10 kD labelled with the P4 and L42 mAbs. This band is not seen in BSE samples. This data was published in June 2007 (L. A. Terry et al. Veterinary record (2007) 160, 873-875). Discussion and Conclusions Here we report the investigation of 501 cattle samples that were submitted to the VLA for BSE diagnosis but subsequently confirmed as negative by the diagnostic test used at the time of submission. Prior to 2000 this was by histology alone and positive diagnosis was made solely upon the observation of vacuolation and gliosis in the relevant brain regions. As a result, using more sensitive diagnostic assays, we were able to diagnose BSE positive cattle from the years 1997-1999 inclusive that were originally negative by vacuolation. From these data we have estimated that approximately 3% of the total suspect cases submitted up until the year 1999 were mis-diagnosed. This is likely to be due to the relative sensitivities of the methods. In addition, it has been demonstrated in cattle that vacuolation occurs after PrPsc can be detected in the brain stem and that PrPsc is detected prior to clinical disease (Arnold et al, 2007). Thus these cattle may have suffering very early clinical signs. However, we have not ruled out the possibility that there may be a subset of BSE affected cattle where vacuolation at the obex does not occur. The two cattle that were positive by the rapid biochemical tests but negative by IHC is an unexplained observation. The samples both contained high amounts of abnormal prion protein as determined by the OD values from the rapid tests that according to our experience of confirmatory testing should have been easily detected by IHC. Furthermore, epitope mapping of the PK cleaved proteins demonstrated no unusual glycoform patterns and IHC evaluation with the same antibodies still did not reveal PrPd deposition in the wax embedded sections. Thus it is unlikely that lack of detection by IHC is the result of an unusual conformation of the PrPd that masks the epitope of R145, the antibody of choice for IHC evaluation at the VLA. The two cattle that were positive by all tests except Bio-Rad ELISA are easier to explain. Previously we have demonstrated that the IDEXX HerdChek scrapie antigen EIA is more analytically sensitive for scrapie than the Bio-Rad ELISA (project SE2007) and this also appears to be the case for bovine BSE. Indeed the two samples were positive by the Bio-Rad Western blot but with significantly reduced signals compared to a bovine positive control. Samples in group 5 were only positive in the Bio-Rad ELISA and only if sub-optimal concentrations of PK were used. Several explanations could account for this result. First, the samples may contain a subset of PrP molecules that have a slightly higher resistance to PK digestion than normal PrPc and that it is not sufficiently aggregated to be detected by the IDEXX assay; whether this is related to a prion disease or some other event that confers such properties on normal PrP remains unanswered. There are notable descriptions in the literature of TSE models where disease is not accompanied by the characteristic accumulation of PK resistant PrP or was found at extremely low levels (Piccardo et al., 2007; Barron et al 2007; Nazor et al., 2005). These findings together might suggest an additional family of neurodegenerative diseases where the infectious form of PrP is not readily detected by our current diagnostic tests. Second, the higher signal could be the result of an increase in the overall amount of PrPc in the samples as discussed in the results and related to up-regulation of PrP in cells resident in the brain or due to influx of inflammatory cells either as a result of damage or the presence of a non-prion related disease. Third, that the PrP in these samples is bound to an unidentified molecule that confers higher PK resistance, or fourth, inhibits proteinase K. IBNC is likely to represent a subset of this group of cattle. Based on these data, our overall conclusion is that a second type of BSE is unlikely to have co-existed at a high prevalence with the classical form in the cattle population during the UK epidemic.
snip...see full text ;
http://randd.defra.gov.uk/Document.aspx?Document=SE1796_8548_FIN.doc
IBNC BSE TSE update ;
Tuesday, November 17, 2009 SEAC NEW RESULTS ON IDIOPATHIC BRAINSTEM NEURONAL CHROMATOLYSIS (IBNC) FROM THE VETERINARY LABORATORIES AGENCY (VLA) SEAC 103/1
http://bse-atypical.blogspot.com/2009/11/seac-new-results-on-idiopathic.html
31 March 2009 - A summary of the 102nd SEAC meeting (35 KB) held on 4th March 2009
snip...
SEAC noted that IBNC appeared to be a rare disease that occurred in older cattle, predominantly as single cases, although it is possible that surveillance may not detect all cases. Biochemical studies suggested that the prion protein may play a role in the disease. However, it is unclear whether the normal form of the protein or an abnormal form is involved. Studies are required to determine whether IBNC is transmissible or not. SEAC concluded, noting that specified risk material controls are in place to prevent cattle brain from entering the food supply, that current data on IBNC do not suggest it presents a risk to human health.
http://www.seac.gov.uk/summaries/seac102_summary.pdf
>>> All of the 15 cattle tested showed that the brains had abnormally accumulated prion protein. <<<
Saturday, February 28, 2009
NEW RESULTS ON IDIOPATHIC BRAINSTEM NEURONAL CHROMATOLYSIS "All of the 15 cattle tested showed that the brains had abnormally accumulated PrP" 2009
SEAC 102/2
http://bse-atypical.blogspot.com/2009/02/new-results-on-idiopathic-brainstem.html
Wednesday, October 08, 2008
Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?
http://bse-atypical.blogspot.com/2008/10/idiopathic-brainstem-neuronal.html
8. I was in receipt of no extra funds beyond those provided by the NHS and the University of London to run my laboratories and pay my salary as a senior lecturer/honorary Consultant and I suffered no constraints over my publications, lectures to my students, or statements to the media. However, I became increasingly aware after 1988 that questioning official dogma about BSE brought difficulties to one’s career. I was myself about to retire from the Charing Cross Hospital, where I worked as a Consultant Neuropathologist, but I observed with horror that the good reputations of dissenting scientists in the field, not least Dr Stephen Dealler and especially Dr Harash Narang were systematically undermined.
http://collections.europarchive.org/tna/20080102135133/http://www.bseinquiry.gov.uk/files/ws/s410.pdf
THEY KNEW 2 DECADES AGO the damn BSE mad cow testing were not finding cases ;
BSE-NON-CONFIRMATION OF DISEASE
3. A question posed by Mr Whaley (para 2) is that classical lesions of BSE may not occur in all cases. Supposing we had a strain variant that produced it's lesions in the cerebrum these would not be detected by our current method. I think this would be unlikely but not impossible - another reason why at least a proportion of complete brains (or blocks) should be retained during the epidemic so if the problem Mr Whaley indicates escalates, it can be investigated.
snip...
5. IF you had the information what benefit would there be ? what would you do with it ?
CONCLUSION
I do not recommend any action. The situation should be accepted. I do not think the VIS can do more at present. The situation should be kept under review particularly if there is an escalation in numbers in this category.
R BRADLEY
15 MAY 1990
90/5.15/3.2
http://collections.europarchive.org/tna/20090505194948/http://bseinquiry.gov.uk/files/yb/1990/05/15003001.pdf
''THE LINE TO TAKE'' ON IBNC $$$ 1995 $$$
1995
page 9 of 14 ;
30. The Committee noted that the results were unusual. the questioned whether there could be coincidental BSE infection or contamination with scrapie. Dr. Tyrell noted that the feeling of the committee was that this did not represent a new agent but it was important to be prepared to say something publicly about these findings. A suggested line to take was that these were scientifically unpublishable results but in line with the policy of openness they would be made publicly available and further work done to test their validity. Since the BSE precautions were applied to IBNC cases, human health was protected. Further investigations should be carried out on isolations from brains of IBNC cases with removal of the brain and subsequent handling under strict conditions to avoid the risk of any contamination.
31. Mr. Bradley informed the Committee that the CVO had informed the CMO about the IBNC results and the transmission from retina and he, like the Committee was satisfied that the controls already in place or proposed were adequate. ...
snip... see full text ;
http://collections.europarchive.org/tna/20080102204938/http://www.bseinquiry.gov.uk/files/yb/1995/06/21005001.pdf
SEAC MINUTES OF THE 19TH MEETING HELD ON 21 JUNE 1995 AT THE CENTRAL VETERINARY LABORATORY
31. Mr Bradley informed the Committee that the CVO had informed the CMO about the IBNC results and the transmission from retina and he, like the Committee was satisfied that the controls already in place or proposed were adequate. ...
http://web.archive.org/web/20030327015011/http://www.bseinquiry.gov.uk/files/yb/1995/06/21005001.pdf
ALSO, please note, atypical BSE-H strain is also transmissible in the humanized transgenic mice with distinct phenotype ;
P26
TRANSMISSION OF ATYPICAL BOVINE SPONGIFORM ENCEPHALOPATHY (BSE) IN HUMANIZED MOUSE MODELS
Liuting Qing1, Fusong Chen1, Michael Payne1, Wenquan Zou1, Cristina Casalone2, Martin Groschup3, Miroslaw Polak4, Maria Caramelli2, Pierluigi Gambetti1, Juergen Richt5*, and Qingzhong Kong1 1Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA; 2CEA, Istituto Zooprofilattico Sperimentale, Italy; 3Friedrich-Loeffler-Institut, Germany; 4National Veterinary Research Institute, Poland; 5Kansas State University, Diagnostic Medicine/Pathobiology Department, Manhattan, KS 66506, USA. *Previous address: USDA National Animal Disease Center, Ames, IA 50010, USA
Classical BSE is a world-wide prion disease in cattle, and the classical BSE strain (BSE-C) has led to over 200 cases of clinical human infection (variant CJD). Two atypical BSE strains, BSE-L (also named BASE) and BSE-H, have been discovered in three continents since 2004. The first case of naturally occurring BSE with mutated bovine PrP gene (termed BSE-M) was also found in 2006 in the USA. The transmissibility and phenotypes of these atypical BSE strains/isolates in humans were unknown. We have inoculated humanized transgenic mice with classical and atypical BSE strains (BSE-C, BSE-L, BSE-H) and the BSE-M isolate. We have found that the atypical BSE-L strain is much more virulent than the classical BSE-C. The atypical BSE-H strain is also transmissible in the humanized transgenic mice with distinct phenotype, but no transmission has been observed for the BSE-M isolate so far.
III International Symposium on THE NEW PRION BIOLOGY: BASIC SCIENCE, DIAGNOSIS AND THERAPY 2 - 4 APRIL 2009, VENEZIA (ITALY)
http://www.istitutoveneto.it/prion_09/Abstracts_09.pdf
BUT yet, USDA scientist even managed to change that science around too, by having the only cow known in the world to date that is familial BSE $ PLEASE NOTE, this so-called BSE with mutated bovine PrP gene (termed BSE-M) that was found in 2006 in the USA. a supposedly new strain of familial BSE ? takes me back to the infamous sporadic FFI, that's not familial ? they don't have a clue, in my opinion. but yet the USDA officials will blame it on anything and everything, but the most likely cause i.e. MAD COW FEED IN COMMERCE. Instead, now we have another new strain of mad cow disease, only this is in the USA, and it is just a spontaneous old cow disease i.e. 'familial h-BSEalabama'.
''We hypothesize that the bovine Prnp E211K mutation most likely has caused BSE in “the approximately 10-year-old cow” carrying the E221K mutation.''
WHAT a hoot. They have now taken the same strain of mad cow disease (h-BSE), that Kong et al in 2009 showed was transmissible to humans via human TG mice, and termed it another new mad cow disease, termed ‘‘U.S. BSE Alabama’’ as being another spontaneous happening from nothing. I swear, this just get's better and better. what about IBNC BSE, no cases yet in the USA ? and just what is IBNC BSE ? (more on that later).
BSE Case Associated with Prion Protein Gene Mutation
Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) of cattle and was first detected in 1986 in the United Kingdom. It is the most likely cause of variant Creutzfeldt-Jakob disease (CJD) in humans. The origin of BSE remains an enigma. Here we report an H-type BSE case associated with the novel mutation E211K within the prion protein gene (Prnp). Sequence analysis revealed that the animal with H-type BSE was heterozygous at Prnp nucleotides 631 through 633. An identical pathogenic mutation at the homologous codon position (E200K) in the human Prnp has been described as the most common cause of genetic CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. A recent epidemiological study revealed that the K211 allele was not detected in 6062 cattle from commercial beef processing plants and 42 cattle breeds, indicating an extremely low prevalence of the E211K variant (less than 1 in 2000) in cattle.
Author Summary Top
Bovine spongiform encephalopathy (BSE or Mad Cow Disease), a transmissible spongiform encephalopathy (TSE) or prion disease of cattle, was first discovered in the United Kingdom in 1986. BSE is most likely the cause of a human prion disease known as variant Creutzfeldt Jakob Disease (vCJD). In this study, we identified a novel mutation in the bovine prion protein gene (Prnp), called E211K, of a confirmed BSE positive cow from Alabama, United States of America. This mutation is identical to the E200K pathogenic mutation found in humans with a genetic form of CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. We hypothesize that the bovine Prnp E211K mutation most likely has caused BSE in “the approximately 10-year-old cow” carrying the E221K mutation.
http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000156
http://www.plospathogens.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.ppat.1000156&representation=PDF
WHAT does this study show. IS it really a novel mutation in the bovine prion protein gene (Prnp), called E211K, of a confirmed BSE positive cow from Alabama, United States of America, the only one in the world ?
How can scientist around the globe continue to believe such junk science coming from the ARS and USDA, and not see through all this, and still continue to want to trade with them ?
maybe I am not suppose to understand all this, or maybe they just wish I couldn't (and I am not claiming to understand all of it). I just know that something is not computing anymore with the UKBSEnvCJD theory, the rest of different atypical TSE, and the USDA and OIE only theory we are suppose to believe in. I see now where Japan and the USA are going to swap out BSE risk for FMD risk, and it's all about trade once again $ I have seen the FDA claim that feeding 5.5 grams of banned mad cow feed at the Purina plant in Gonzales Texas to each cow was not enough of the TSE agent to worry about. I have seen the TDAH and or the USDA et al completely cover up a highly suspect stumbling and staggering mad cow, sent straight to be rendered without any test at all for mad cow disease and then just claim ignorance, but we knew it was ordered from higher up officials. then we watched another mad cow in Texas, that was confirmed by a secret test to be a positive test, but yet this cow was ordered to be negative, until it took an act of Congress, and 7 months later and scientist complaining from around the globe, that this cow should be re-tested. IT was and it was CONFIRMED 7 months later. I have seen, and it was proven that part of the infamous June 2004 enhanced BSE surveillance and testing program was a sham, they were getting healthy brains from cattle they knew did not have mad cow disease and submitting them for testing. The were busted for that too. It was proven to be true. Then another 9,200 cows in the same program used a test least likely to find mad cow disease i.e. the IHC. oh yea, they did everything they could to claim the Washington cow that was positive, was not a USA cow, and in the end it worked, the suspect mad cow that was suppose to be from the USA, well that was not the right cow, it was another one, this one from Canada. after the back to back h-familial-BSE in Alabama, and h-BSE(whatever they come up with later) in Texas, right after these two cows were documented, they saw the writing on the wall and shut the testing down to numbers so low, it's now mathematically impossible to detect a mad cow case in the USA. what I have seen in these 13+ years is politics manipulate science, and it's not pretty.
The OIE and USDA et al sold there soul to the devil, and in doing so, they sold yours too.
EU IBNC BSE, ANOTHER OLD COW DISEASE, is m-BSE i.e. h-familial-BSE in Alabama only, is this EU IBNC BSE ???
OR, is this just another case of mad cow disease officials are trying to pawn off as something else $$$
Let's look at this closer.
h-familial-BSE in Alabama case
Obvious lesions of spongiform encephalopathy diagnostic for BSE were not present in the brainstem, however it was positive for the presence of PrPd by IHC (Figure 1B). Distribution of PrPd in the brainstem of this animal was not as uniform or as intense as seen with the C-type U.S. BSE case from 2003 (Figure 1C) [4]
Immunohistochemistry
Brain tissue was placed in 10% buffered formalin and after a minimum of 4 days of fixation appropriate sections of brainstem in the obex region were put in cassettes and kept in fresh formalin until they were processed for routine paraffin embedding. The procedure was described in detail previously [4]. The IHC results were interpreted as follows: (i) positive for PrPd: pink to red and (ii) background and negative for PrPd: only blue background. As positive controls, slides from the brainstem of a BSE-positive cow, obtained from the United Kingdom and from the U.S. BSE Case 2003 were used. As negative controls, slides from brainstem material of BSE-negative cattle and scrapie-negative sheep were used.
http://www.plospathogens.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.ppat.1000156&representation=PDF
IBNC BSE, that's not BSE, but is another novel prion disease.
Atypical prion proteins in cattle DEFRA project code SE1796 FOIA Final report
snip...
Investigation of the distribution and molecular characteristics of PrP from known IBNC
See also: Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?
Jeffrey M, Perez BB, Martin S, Terry L, González L.
BMC Vet Res. 2008 Sep 30;4:38
Further investigations demonstrated that 57% the assays performed on the confirmed IBNC samples, using the 0.3 Bio-Rad TeSeE assay (n=42), gave values above those of the test kit control and also the BSE negative brain pool control.
Half brains from six IBNC affected animals were retrieved from the TSE archive alongside the brainstem from a seventh animal. The cortex, brainstem, cerebellum and midbrain from these brains were sub-sampled and the adapted Bio-Rad TeSeE EIA, IDEXX Herdchek and Western Blot protocols applied to these tissues, in order to determine whether they could represent a form of atypical BSE. These samples had previously been found to be negative using the commercial Bio-Rad EIA and re-testing using this assay and the IDEXX Herdchek assay confirmed their negative status. When assayed using the adapted Bio-Rad protocol at 0.3µl/ml PK, 24/42 (57%) of the sample assays performed gave values above those of the test kit control and also the BSE negative brain pool control. Values above twice that of the calculated cut-off levels were found for each case but not for each brain site
No PrPres was detected when Western blotting these samples at either 20 or 4µl/ml PK but a signal was detected on the gels when blotted at the 0.12 and 0.3µl/ml PK levels. At 0.12µl/ml PK the IBNC samples were indistinguishable from the negative controls but at the 0.3µl/ml level more PrPres was detected in the IBNC cases than in the controls with each of the antibodies tested (SHA31, F99, SAF84 and P4). Illustrations of the F99 blot are shown in the paper. Other data not shown.
These data suggest that IBNC affected cattle abnormally express or accumulate PrP in brain and that the abnormal PrP is not strongly resistant to protease digestion. The results suggest that either the range of prion diseases is still wider than previously thought or that abnormalities of prion protein expression may be associated with brain lesions unconnected with prion disorders. Biochemical and transmission studies are planned in order to investigate further (under SE2014).
http://randd.defra.gov.uk/Document.aspx?Document=SE1796_8548_FIN.doc
c-BSE, atypical l-BSE, atypical h-BSE, m-BSE and or atypical familial h-BSEalabama, IBNC
just what is this IBNC and or the m-BSE in the bovine, and or could they be the same ?
are they just another strain of BSE ?
TSS
Executive Summary
Studies of Bovine Spongiform Encephalopathy (BSE), carried out in the UK, showed it to be a single strain of prion disease based on histopathological (Simmons et al., 1996) and transmission data (Bruce et al., 1992 ). First reported in the 1980s (Wells et al., 1987) there appears to have been little change in the characteristics of the disease throughout the epidemic and BSE maintains a distinct molecular profile even following cross species transmission. However, during surveillance programmes in Europe and in North America two other distinct isolates of bovine prion disease have come to light, H and L type, so-called to reflect their unique molecular profiles (Yamakawa et al., 2003; Biacabe et al., 2004).
Reports were also emerging of atypical forms of scrapie that were distinct from classical scrapie isolates and were less easily recognised by the then current diagnostic tests (Benestad et al., 2003; Buschman et al., 2004). This led to concerns that cattle could also harbour a prion disease that was not detected by the current diagnostic tests for BSE. Importantly, approximately 15-20% of the clinical cases submitted for investigation were indeed negative and this proportion of negative cattle did not appear to vary despite increasing awareness of BSE clinical signs by the farming and veterinary community. While there maybe other explanations for this discrepancy (McGill et al., 1993), another underlying undiagnosed prion disease of cattle distinct from classical BSE could not be ruled out.
The study reported here investigated a small number of these BSE negative clinical cases by using more sensitive and modified diagnostic tests for abnormal PrP.
The majority of the cases that we studied were negative by all the tests employed and based on this observation we conclude that there was not a simultaneous epidemic of another form of bovine prion disease. However, we observed a number of classical cases that were missed prior to the advent of sensitive and rapid diagnostic tests and this provides an estimate of the number of cattle that were mis-diagnosed before 2000. In addition, we observed a few rare cases where the diagnostic tests were not in agreement and these cases were investigated further. One of these unusual samples emerged as a case of idiopathic bovine neuronal chromatolysis (IBNC).
During the study we also reported the first H-type BSE case in the UK (Terry et al., 2007).
snip...
Scientific Objectives as prescribed in the project:
All of the objectives have been met and are described in detail below. Three annexes accompany this report, one with the figures for the results below and two papers for submission to peer-reviewed journals.
Objective 1:
To determine the variation of PK sensitivity of bovine PrPc from uninfected cattle brains and compare with bovine PrPsc from classical cases of BSE in order to set thresholds for negative, weak and strong positive values in commercially available rapid diagnostic tests.
Objective 2:
Determine whether there are a greater proportion of bovine brain samples positive for the rapid diagnostic tests (hereby called reactors) in the clinically-suspect, negative subset of cattle than in healthy negative cattle. (True positives will be determined on the basis of evaluation by IHC but should be strongly positive in both the rapid diagnostic tests).
Objective 3:
Determine whether the phenotypic and molecular characteristics of PrP from cattle identified in 2 are distinct from normal PrPc and from bovine PrPsc normally associated with classical BSE.
Studies of Bovine Spongiform Encephalopathy (BSE), carried out in the UK, showed it to be a single strain of prion disease based on histopathological (Simmons et al., 1996) and transmission data (Bruce et al., 1992). First reported in the 1980s (Wells et al., 1987) there appears to have been little change in the these characteristics of the disease throughout the epidemic; BSE also appear to maintain a distinct molecular profile in cattle and even when experimentally (or naturally) transmitted to other species such as humans and cats. However, during surveillance programmes in Europe, Japan and in North America, two other distinct isolates of bovine prion disease have come to light, H and L type, so-called to reflect their unique molecular profiles (Yamakawa et al., 2003; Biacabe et al., 2004).
In the late 1990’s, a novel prion disease was discovered in sheep (Benestad et al., 2003; Buschman et al., 2004); this Nor98 or atypical scrapie is widespread in Europe but had previously been missed by histopathological or immunohistological examination. This led to concerns that cattle could also harbour a prion disease that, unlike H- and L-type BSE, was not detected by the current diagnostic tests for BSE. Importantly, approximately 15-20% of the clinical cases submitted for investigation were indeed negative and this proportion of negative cattle did not appear to vary despite increasing awareness of BSE clinical signs by the farming and veterinary community. While there maybe other explanations for this discrepancy (McGill et al., 1993), another underlying undiagnosed prion disease of cattle distinct from classical BSE could not be ruled out.
The study reported here investigated a small number of these BSE negative clinical cases by using more sensitive and modified diagnostic tests for abnormal PrP. The majority of the cases that we studied were negative by all the tests employed and based on this observation we conclude that there was not a simultaneous epidemic of another form of bovine prion disease. However, we observed a number of cases of BSE in this “BSE negative” sub-set that were missed prior to the advent of more sensitive and rapid diagnostic tests and this provides an estimate of the number of cattle that were mis-diagnosed before 2000. In addition, we observed a few rare cases where the diagnostic tests were not in agreement and these cases were investigated further. One of these unusual samples emerged as a case of idiopathic bovine neuronal chromatolysis (IBNC) (Jeffrey & Wilesmith, 1992; 1996; Jeffrey et al., 2009).
During the study we also reported the first H-type BSE case in the UK (Terry et al., 2007).
Materials and Methods
Tissue samples.
Test samples: Frozen brain stem from 501 bovine BSE suspects with neurological signs, a) that were negative at the level of the obex for vacuolation by standard histopathological techniques from years 1991-1999 and b) by IHC and diagnostic Bio-Rad PlateliaTM from 2000 onwards. These tissues have been stored at the VLA at –80oC since submission.
Negative controls: Frozen brain stem from 90 cattle investigated as part of the active surveillance programme. These samples were submitted in 2006 to LGC for rapid testing by Bio-Rad TeSeE diagnostic ELISA and were negative. These samples were stored at –80oC prior to testing and were stored for a maximum of 36 months and therefore considerably less time than all experimental samples under investigation.
Cattle with suppurative encephalitis: 10 additional cattle samples were retrieved from the VLA Archive that were negative for BSE but showed signs of suppurative encephalitis and inflammation (lymphocyte cuffing and gliosis). These signs were consistent with listeria infection.
Tests for disease-associated PrP
IDEXX BSE Herdchek BSE antigen test kit
All samples were assayed using the IDEXX Herdchek Bovine Spongiform Encephalopathy (BSE) Antigen Test Kit, EIA according to the manufacturer’s instructions and without modification. Briefly, brains were homogenised in the buffer provided by the manufacturer and diluted prior to adding to the seprion (polyanion) coated multiwell plate and incubated prior to washing. The samples were then treated with a conditioning buffer to expose the antigen epitopes. PrPsc was detected by PrP specific antibodies conjugated to horseradish peroxidase and visualised with TMB substrate. Samples were read using a microtitre plate reader (Victor-Perkin-Elmer). The method has no Proteinase K digestion step and has only a mild trypsin treatment that is not required for specificity but aids in the epitope exposure step. The normal curve of negative control samples is provided by the manufacturer and shows the diagnostic cut off value is set higher than most negative controls. The amount of brain added to a single well is approximately 20 mg.
Diagnostic Bio-Rad TeSeE EIA
Sample extraction and detection was carried out according to the manufacturer’s instructions for the Bio-Rad TeSeE BSE ELISA. Briefly brain samples were homogenised in buffer provided by the manufacturer and then treated for 10 mins with Proteinase K at 37oC . The PK concentration is not provided by the manufacturer so we refer to it as 4 ul/ml which is the quantity of stock PK to final solution directed by Bio-Rad. A comparison with sigma PK indicated that the concentration is approximately 40 ug/ml. The samples were then precipitated and concentrated by centrifugation. Pellets were reconstituted and diluted in the buffers provided by the manufacturer. The PrPsc was then detected by a sandwich ELISA provided by the manufacturer. Details of the antibodies are not provided. Samples are read using a microtitre plate as above. Cut off values for the ELISA are calculated using the mean of four negative control ODs. The manufacturers indicate that a value of 0.14 should be added to the negative control mean and samples equal to or greater than this value should be further analysed. The amount of brain added to a single well is approximately 65 mg.
BioRad TeSeE EIA with reduced PK digestion (0.3 Bio-Rad TeSeE ELISA)
The PrPsc associated with atypical scrapie is believed to be less PK resistant than classical scrapie (Everest et al., 2006). In order to investigate whether an atypical form of BSE in cattle exists biochemically similar to atypical scrapie a modified version of the Bio-Rad TeSeE protocol, using sub-diagnostic levels of Proteinase K (0.3ul/ml), was used. This quantity of PK was arrived at by titration of PK and digestion of PrPc from 47 cattle brains negative for TSEs.
The Bio-Rad TeSeE BSE diagnostic test was used as directed by the manufacturer with the addition of DNAse prior to the Proteinase K (0.3 ul/ml PK) treatment and Pefabloc was added alongside the kit PK stopping solution. The PK dilution for these assays was prepared from a Sigma stock solution and 0.3 units/ml was the equivalent activity as 0.3 ul/ml of Biorad PK.
Bio-Rad TeSeE Western Blot
Sample extraction was carried out according to the manufacturer’s instructions (Bio-Rad TeSeE Western Blot) with several modifications. In brief, brain tissue was ribolysed to give 20 % (w/v) homogenate and subsequently incubated with DNAse. The samples were then digested with 0.3, 1, 4 or 20 units/ml PK (Sigma; where units/ml is an in-house nomenclature and 0.3 units/ml is equivalent to 0.3 µl of the Bio-Rad test PK in terms of activity as compared using the TAME test -Pierce) and the reaction stopped with Pefabloc. Following precipitation and centrifugation at 15,000 g for 7 minutes, in accordance with the Bio-Rad TeSeE Western blot protocol, the pellets were re-suspended in Laemmli sample buffer.
For analysis, the supernatants were heated at 100oC for 5 minutes, loaded on a 12% Criterion XT Bis-tris SDS gel (Bio-Rad) and subjected to electrophoresis in XT-MOPS running buffer (Bio-Rad) at 200 V for 50 minutes. Proteins were transferred to a PVDF membrane (Bio-Rad) at 115 V, 60 min using Tris/CAPS transfer buffer (Bio-Rad).
Blots to be evaluated using the Sha31 (Bio-Rad) antibody were incubated for one hour with the blocking solution provided by the manufacturers; and antibodies SAF84 (aa 175-180), P4 (aa 89-104) and FH11 (aa 55-65) using a 5% milk powder in PBS supplemented with Tween 20 (PBST). The membranes were incubated for one hour with the primary antibody and then with goat anti-mouse IgG antibody conjugated to horseradish peroxidase (Bio-Rad) prior to visualization by chemiluminescence (ECL; Amersham).
Immunohistochemical analysis
Formalin-fixed, paraffin wax-embedded tissue blocks were sectioned at 4mm, collected onto frosted charged slides (GmbH) and melted on at 60°C overnight to improve adhesion. Sections were de-waxed in xylene and alcohol and washing in water. They were subsequently put into 98% formic acid (Merck) for 30 minutes, washed in running tap water for 15 minutes and then fully immersed into citrate buffer (200mM trisodium citrate dehydrate (Sigma), 30mM citric acid (Sigma), pH 6.1) prior to being autoclaved for 30 minutes at 121°C. Endogenous peroxidase activity was quenched using 3% hydrogen peroxide (Sigma) and the sections immersed in purified water and stored at 4°C overnight. After warming to room temperature, non-specific antibody binding sites were blocked using normal goat serum (Vector Laboratories) for 20 minutes. Rat monoclonal anti-PrP R145 (VLA) was diluted to 2mg/ml and applied for one hour at ambient (19°C-24°C) temperature. Biotinylated rabbit-anti-mouse IgG (Vector Laboratories) was diluted appropriately and applied for 30 minutes at ambient temperature. Elite ABC (Vector Laboratories) was prepared according to the manufacturers’ directions and applied for 20 minutes at ambient temperature. Sections were washed between each stage using 5mM tris buffered saline supplemented with Tween-20 (5mM tris, 0.85% NaCl, 0.05% tween-20 (all from Sigma), pH 7.6). Diaminobenzidine tablets (Sigma) were prepared in McIlvanes buffer (200mM disodium hydrogen orthophosphate, 100mM citric acid (both from Sigma), pH 6.4) and applied for 10 minutes at ambient temperature. Sections were counterstained in Mayer’s haematoxylin and “blued” in running tap water, before being dehydrated through three changes each of absolute alcohol and xylene for three minutes each and finally mounted in DPX (Sigma).
Definition of terms
Disease associated isoforms of PrP may be distinguished from normal PrP by its increased resistance to Proteinase digestion in immunoblotting or ELISA tests (PrPres), binding to polyanions or labelling with PrP specific antibodies in fixed and treated paraffin-embedded section (PrPd). Included within the operational definition of PrPd are all those detection systems that do not use Proteinase K digestion. The correlation between prion infectivity and PrPres or PrPd is inexact, and infectivity has been dissociated from PrPres or PrPd in several experiments, putatively this is because only a fraction of abnormal PrP isoforms are infectious. We will therefore use operational definitions for detected abnormal PrP forms and PrPsc for the hypothetical infectious sub-population of PrP isoforms detected by bioassay.
Results
Brains from cattle previously diagnosed as negative for BSE based on histopathological examination were investigated in this study for evidence of unusual prion diseases. The majority of the cattle investigated were submitted to the VLA as BSE suspect during the years 1997-2005 and were reported to have clinical signs similar to BSE. We applied a combination of modified and previously unused diagnostic tests to this subgroup of cattle including lower concentrations of PK for protein digestion, tests that do not use PK for PrPsc detection and standard Western blot (WB) procedures with Mabs reactive with different regions of the PrP glycoprotein. A flow chart detailing the sequence for the investigation of potential unusual prion diseases of cattle are shown in Figure 1.
1) Determination of the lowest PK concentration that digests PrPc from brains of cattle
The minimum concentration of PK required for the elimination of PrPc in the majority of non-exposed control cattle samples, resulting in a negative value in the Bio-Rad TeSeE ELISA, was determined. PK titrations were performed on BSE positive and negative control reference material (CRM) and subsequently on 47 individual confirmed negative brainstems. The brainstems had previously tested negative with the diagnostic Bio-Rad TeSeE ELISA by LGC and were obtained from active surveillance and therefore unlikely to have had clinical signs of disease. An amount of 0.3 µl/ml PK was selected for use in the adapted Bio-Rad TeSeE ELISA (0.3 Bio-Rad) (Table 1).
2) Determination of threshold values for the IDEXX HerdChek and 0.3 modified Bio-Rad rapid tests
The diagnostic tests have cut-off values that are set by the manufacturers. For the 0.3 Bio-Rad ELISA new cut-off values were determined to take account of the modifications. While no modifications were made to the IDEXX HerdChek assay cut-off values were calculated using the same test samples for consistency. 90 confirmed BSE negative brainstems were assayed and threshold values calculated as 3 standard deviations above the mean (Table 2). Threshold values of 0.166 Absorbance Units (AU) and 0.137 AU were set for the 0.3 Bio-Rad TeSeE and IDEXX Herdchek EIAs respectively. A single confirmed negative sample gave a value above the IDEXX threshold limit (0.240AU) on first assay. However, when repeated this sample was negative (0.016AU).
3) Results of assays applied to the test BSE cattle population
The assays described above and mapped in Figure 1 were then applied to the brains from 501 clinically suspect cattle. Following analysis the cattle were divided into five groups and these are described below. The results are summarised in Table 3.
Group1: Confirmed negative diagnosis of clinically suspect cattle
Brainstems from 501 cattle submitted to the VLA for BSE diagnosis between the years 1991 and 2005 that were subsequently diagnosed as negative by the tests used at time of slaughter, were assayed using the IDEXX and 0.3 Bio-Rad immunoassays for detection of abnormal PrP. 436 (87%) were negative by both tests. All of the samples submitted after 1999 were confirmed negative (see below) (Figure 8). By these criteria we were unable to detect abnormal PrP in the brainstems of these cattle and this subset of clinically suspect cattle is unlikely to harbour a prion disease. However, we were unable to test other areas of the brain from these cattle and PrPsc distribution patterns distinct from classical BSE cannot be ruled out. In addition to the 501 brainstems we also tested 191 cerebella by the same methods, all of which were negative by standard tests.
Group 2: Confirmed positive for BSE by all diagnostic tests
Sixty five samples remained that were positive in either the IDEXX or the 0.3 Bio-Rad assays or in both of these tests. Of these, 40 were positive by both tests (modified as above) and following retesting were positive using diagnostic concentrations of PK for the Bio-Rad TeSeE (figure 2). Immunohistochemical evaluation of abnormal PrP in the obex demonstrated normal distribution of PrPsc deposits similar to those observed for classical BSE (Figure 8).
To confirm that the PK resistant glycoproteins of abnormal PrP resembled the molecular profile of classical BSE, all 40 cases were immunoblotted using SHa31 MAb (figure 3). In all cases a signature 3 glycoprotein banding pattern was observed with relative mass and glycoprotein ratios indistinguishable from classical BSE. These animals ranged in age from 5 years to 12 years, with a mean age of 6 years, 10 months. All 40 animals were female and comprised 32 Friesians, 2 Holsteins, 2 Herefords, 1 Limousin/Friesian Cross, 2 Holstein/Friesian Cross and 1 Simmental.
The 40 confirmed positive samples were from cattle slaughtered between the years 1997 and 1999. We tested a total of 285 from this period and this represents 14.0% of the clinical suspects that were confirmed negative for BSE at this time. If this is representative of the entire clinical suspect unconfirmed cattle (total 2,426) during this period (1997-1999 inclusive) a total of 340 BSE positive cattle would have been missed. This under-diagnosis is likely to be a result of the diagnostic tests applied at the time. Up until the year 2000, all BSE cases were diagnosed by detection of vacuolation and gliosis in the obex. It is clear that this method is not 100% sensitive for prion diseases either because not all cases present with vacuolation or that vacuolation is a late onset phenomenon during clinical disease (Arnold et al., 2007). Our data showed that there were no additional cases of under-diagnosis after more sensitive diagnostic tests were introduced in 2000. During the years 1997-1999, a total of 12,171 clinical cases were submitted for BSE diagnosis of which 9,745 (80.1%) were confirmed positive with an estimated 2.8% of the total suspects submitted under-diagnosed by our calculations.
Assuming no other factors influenced the levels of correct diagnosis and that the numbers estimated for 1997 to 1999 were a true representation of the potential under-diagnosis of the entire epidemic up until 1999, then the total number of missed cases positive for BSE could have been in the region of 5,500.
A draft version of this manuscript has been prepared.
Group 3: Confirmed positive for BSE by all rapid diagnostic tests but negative by IHC
2 of the 501 negative subset brainstem tested were positive by standard biochemical, diagnostic tests (Table 4) but abnormal PrP deposits were not observed in the obex when evaluated by IHC (Figure 8). This is clearly an unusual finding and both cases were rigorously audited prior to further investigation to determine that the sample for biochemistry was identical to the paraffin-embedded sample. As far as can be determined no errors in sampling and dispatch occurred for these two samples. Further DNA profiling and matching frozen sample to histology processed sample would confirm this. There was insufficient sample to perform any further analysis on one case, but the other case was further investigated using the modified TeSeE Western blot protocol described above – at the diagnostic standard PK concentration of 4 µl/ml for PrPsc digestion. Western blotting of abnormal PrP from this sample confirmed the ELISA data with intense labelling of PK resistant PrP using the PrP-specific antibodies Sha31 and SAF84 (Figure 4a and 4b). The glycoprofile and molecular mass of the PrP bands were indistinguishable from classical BSE A band was labelled strongly with FH11 Mab (that recognises an N terminal PrP epitope) and is therefore likely to represent undigested PrP (Figure 4c). In addition, at 4 µl/ml PK, strong reactivity is also observed with the P4 mAb (Figure 4d). Molecular comparison of this case with classical BSE and with scrapie – using different levels of PK, different dilutions of positive sample and different PrP-specific antibodies, indicates that there is no discernible difference of the test sample with classical BSE. Both cases were extensively followed up by IHC using Mabs to different regions of the PrP molecule but were negative in all cases (data not shown).
Why the PrPsc could not be detected by IHC is unclear. Further analysis by transmission to rodent models of prion disease may shed further light on the characteristics of this sample. Indeed, murine models of prion disease have been reported where PrPsc cannot be detected in the brains but these studies confirmed the lack of PrPsc by all assays including Western Blot.
Group 4: IDEXX Herdchek positive, 0.3 Bio-Rad negative, IHC positive.
Two brainstem samples (98/00819; 98/02316) were positive by the IDEXX Herdchek EIA (Table 5) but Bio-Rad test negative even following PK digestion at sub-optimal concentrations. Both of these samples demonstrated abnormal PrP deposition in the obex by IHC evaluation (Figure 8). Western blot analysis of PK resistant PrP glycoprotein from sample 98/2316 indicated that low amounts of PrPres could be detected using Sha31 and SAF84 Mabs. From these blots and taking into account the low levels of PrPres detected the banding patterns appeared indistinguishable from classical BSE (Figure 5a and 5b). No further sample was available for 98/00819.
The sample contained very low levels of PrPres as shown by the WB data and this is likely to be the reason for lack of signal in the Bio-Rad ELISA. At these levels of abnormal PrP we are at the threshold of detection. The IDEXX HerdChek assay has consistently shown a higher analytical sensitivity for classical scrapie in our hands than the Bio-Rad assays. The values for the IDEXX HerdChek were in the region of 0.15-0.88 and these values are much lower than any of the other samples we have tested in this study. These data suggest that the IDEXX assay is more analytically sensitive than the Bio-Rad TeSeE for BSE.
However, there are alternative explanations for the discordance in test results. The Bio-Rad TeSeE ELISA detects PrPres with Mabs that detect 2 regions of the molecule. Any changes in PrP sequence in the region of Mab binding could alter analytical sensitivity. Therefore the bovine PrP open reading frame from 98/02316 was compared with that of two classical BSE samples, all three samples were 6:6 with respect to the octapeptide repeat. The only mutation seen in this unusual sample was at codon 78 and this is a “silent” mutation in that it does not affect the PrP protein sequence (glutamine, Q78). The Western blot results suggest that the PK cleavage sites of sample 98/02316 were not different from classical cases of BSE. Therefore we conclude that PrPres concentration in this sample was low, as indicated by the control BSE positive brain homogenate, when diluted to a level of 1/250, still producing bands of a far greater density than the test sample when assayed neat.
Group 5: Diagnostic Bio-Rad and IDEXX negative, IHC negative but 0.3 Bio-Rad positive
Twenty-one of the clinical suspect brainstems tested by 0.3 Bio-Rad modified protocol had OD values above the calculated cut off point (range 0.166 to 0.857) (Figure 6) but were IDEXX Herdchek negative and IHC negative (figure 8). The samples were also diagnostic Bio-Rad TeSeE negative and the cattle, all female, ranged in age from 3 years to 11.5 years. They comprised Friesian, Friesian/Holsten, Hereford Cross, Aberdeen Angus Cross, Simmental Cross and Limousin Cross breeds. These samples, where sufficient tissue was available, were analysed, for the presence of partially PK resistant PrP, using the Bio-Rad Western blot protocol with digestion carried out at 20 and 0.3 µl/ml of PK and detected using the SHa31 Mab. Following digestion of the samples with 20 µl/ml PK the samples were shown to be negative for the characteristic PrPsc banding patterns when compared to three individual BSE-negative samples and a classical BSE positive sample (Fig 7a). However, faint bands were observed at approximately 16 and 25 KDa for 4 of the samples (T5, T8-T10) but this faint banding is consistent with partially digested PrPc but could also be a result of variable amounts of protein loaded per lane. At 0.3 µl/ml PK, banding is observed for all test samples, with banding consistent with partially digested PrPC, as also observed for the three known BSE-negative samples. In contrast, the classical BSE-positive sample gave a distinct banding pattern, different from that observed for the BSE-negative samples (Fig.7b). Consistent with the above results samples T5 and T8-T10 demonstrated increased intensity of labelling that could result from an up-regulation or increase in PrPc and could also account for the high signals in the modified ELISA.
Variable banding intensity between lanes may also be a result of inconsistent loading of amounts of protein per lane. However, our previous experience of testing protein concentrations PRIOR to PK digestion in the individual samples showed that they were very consistent to within <5% of the total amount. In addition, although we add pefabloc to stop PK digestion it is also likely that there is variation in the PK digestion amongst samples. Both variables could account for the differences in intensities between lanes. However, we cannot exclude the possibilitity that a PK sensitive variant of abnormal PrP is present as demonstrated by Barron et al 2007 who also demonstrated a 22 KDa band following sub optimal PK digestion. The samples were further investigated as below. Encephalitis may up regulate PrPc One explanation for high values in the immunoassay following digestion with suboptimal concentrations of PK could be high levels of PrPc in the sample. Increased levels of PrPc may occur as a result of up-regulation of PrPc on tissue resident cells or from the influx of inflammatory cells into the site following infection. Differential diagnoses were available for 9 of the 21 animals and nine had confirmed encephalitic lesions and inflammation. Further to this observation we therefore analysed brainstems from 10 BSE negative cattle (but also clinical suspects) by both modified rapid tests that had confirmed encephalitis. The brainstems from 9 encephalitis cattle were negative by both the 0.3 Bio-Rad TeSeE and IDEXX assays. The brainstem from 1 animal was positive by the 0.3 Bio-Rad assay but negative by the IDEXX EIA. The result from this sample is similar to the 21 observed above in group 5. It is unclear therefore whether the high levels of PrP are a result of concurrent infection as there is not a 100% correlation. However, PrPc is more susceptible to endogenous proteases and a low signal could be partly explained by inappropriate handling of the tissue at post-mortem. Loss of PrP detection following retesting of group 5 samples. When all 21 samples were re-analysed from a fresh piece of tissue from the archive (likely to have been frozen and thawed by the archive staff) only one retested as positive (figure 6). Further analysis of this sample (sample number 99/00514) by Western blot has not shown any bands suggesting the presence of an atypical form of prion protein. Any PK sensitive PrP, whether PrPc or unusual prion disease-associated PrP, is likely to be affected by tissue handling techniques including freezing, thawing and the amount of time in storage. This could explain loss of signal. These samples may also represent a small number of outliers in the negative population. This is still higher than we would expect given that only 1/90 negative control samples were outliers in the original testing. Identification of Idiopathic Brainstem Neuronal Chromatolysis (IBNC) in group 5 samples One of the 21 samples identified in group 5 was shown to have IBNC following histological investigation (03/00002) (figure 8). Concurrently, we investigated the PrP distribution in known cases of IBNC (Jeffrey et al 2008; “Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?” BMC Vet Res. 2008 Sep 30;4:38. The IHC and histology profile of this case was very similar to that of the known IBNC cases. Investigation of the distribution and molecular characteristics of PrP from known IBNC See also: Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle? Jeffrey M, Perez BB, Martin S, Terry L, González L. BMC Vet Res. 2008 Sep 30;4:38 Further investigations demonstrated that 57% the assays performed on the confirmed IBNC samples, using the 0.3 Bio-Rad TeSeE assay (n=42), gave values above those of the test kit control and also the BSE negative brain pool control. Half brains from six IBNC affected animals were retrieved from the TSE archive alongside the brainstem from a seventh animal. The cortex, brainstem, cerebellum and midbrain from these brains were sub-sampled and the adapted Bio-Rad TeSeE EIA, IDEXX Herdchek and Western Blot protocols applied to these tissues, in order to determine whether they could represent a form of atypical BSE. These samples had previously been found to be negative using the commercial Bio-Rad EIA and re-testing using this assay and the IDEXX Herdchek assay confirmed their negative status. When assayed using the adapted Bio-Rad protocol at 0.3µl/ml PK, 24/42 (57%) of the sample assays performed gave values above those of the test kit control and also the BSE negative brain pool control. Values above twice that of the calculated cut-off levels were found for each case but not for each brain site No PrPres was detected when Western blotting these samples at either 20 or 4µl/ml PK but a signal was detected on the gels when blotted at the 0.12 and 0.3µl/ml PK levels. At 0.12µl/ml PK the IBNC samples were indistinguishable from the negative controls but at the 0.3µl/ml level more PrPres was detected in the IBNC cases than in the controls with each of the antibodies tested (SHA31, F99, SAF84 and P4). Illustrations of the F99 blot are shown in the paper. Other data not shown. These data suggest that IBNC affected cattle abnormally express or accumulate PrP in brain and that the abnormal PrP is not strongly resistant to protease digestion. The results suggest that either the range of prion diseases is still wider than previously thought or that abnormalities of prion protein expression may be associated with brain lesions unconnected with prion disorders. Biochemical and transmission studies are planned in order to investigate further (under SE2014). First case of H-type BSE identified in GB During the course of this study, 1/5 frozen brainstem from bovine BSE cases when immunoblotted using the Bio-Rad TeSeE Western blot with antibodies P4, L42, 6H4, Sha31 and SAF84, was found to have a PrP profile indistinguishable from French H-type BSE. This sample was the first case of H-type BSE to be identified in GB. It was a fallen 13-year-old Galloway cow, first tested and confirmed as a case of BSE in November 2005. Due to autolysis its brain was unsuitable for further characterisation by IHC. Its age and reported absence of clinical signs are consistent with other cases of H-type BSE. When blotting the samples, mAbs Sha31 and 6H4 revealed, in this sample, an unglycosylated band with relative mobility less than BSE, and mAb P4, labelled the sample more strongly than the BSE samples hence supporting the observed similarities with the French H-type sample. Additionally, this study revealed in both this unusual sample and the French H-type a lower molecular weight band with relative mobility of between 6 and 10 kD labelled with the P4 and L42 mAbs. This band is not seen in BSE samples. This data was published in June 2007 (L. A. Terry et al. Veterinary record (2007) 160, 873-875). Discussion and Conclusions Here we report the investigation of 501 cattle samples that were submitted to the VLA for BSE diagnosis but subsequently confirmed as negative by the diagnostic test used at the time of submission. Prior to 2000 this was by histology alone and positive diagnosis was made solely upon the observation of vacuolation and gliosis in the relevant brain regions. As a result, using more sensitive diagnostic assays, we were able to diagnose BSE positive cattle from the years 1997-1999 inclusive that were originally negative by vacuolation. From these data we have estimated that approximately 3% of the total suspect cases submitted up until the year 1999 were mis-diagnosed. This is likely to be due to the relative sensitivities of the methods. In addition, it has been demonstrated in cattle that vacuolation occurs after PrPsc can be detected in the brain stem and that PrPsc is detected prior to clinical disease (Arnold et al, 2007). Thus these cattle may have suffering very early clinical signs. However, we have not ruled out the possibility that there may be a subset of BSE affected cattle where vacuolation at the obex does not occur. The two cattle that were positive by the rapid biochemical tests but negative by IHC is an unexplained observation. The samples both contained high amounts of abnormal prion protein as determined by the OD values from the rapid tests that according to our experience of confirmatory testing should have been easily detected by IHC. Furthermore, epitope mapping of the PK cleaved proteins demonstrated no unusual glycoform patterns and IHC evaluation with the same antibodies still did not reveal PrPd deposition in the wax embedded sections. Thus it is unlikely that lack of detection by IHC is the result of an unusual conformation of the PrPd that masks the epitope of R145, the antibody of choice for IHC evaluation at the VLA. The two cattle that were positive by all tests except Bio-Rad ELISA are easier to explain. Previously we have demonstrated that the IDEXX HerdChek scrapie antigen EIA is more analytically sensitive for scrapie than the Bio-Rad ELISA (project SE2007) and this also appears to be the case for bovine BSE. Indeed the two samples were positive by the Bio-Rad Western blot but with significantly reduced signals compared to a bovine positive control. Samples in group 5 were only positive in the Bio-Rad ELISA and only if sub-optimal concentrations of PK were used. Several explanations could account for this result. First, the samples may contain a subset of PrP molecules that have a slightly higher resistance to PK digestion than normal PrPc and that it is not sufficiently aggregated to be detected by the IDEXX assay; whether this is related to a prion disease or some other event that confers such properties on normal PrP remains unanswered. There are notable descriptions in the literature of TSE models where disease is not accompanied by the characteristic accumulation of PK resistant PrP or was found at extremely low levels (Piccardo et al., 2007; Barron et al 2007; Nazor et al., 2005). These findings together might suggest an additional family of neurodegenerative diseases where the infectious form of PrP is not readily detected by our current diagnostic tests. Second, the higher signal could be the result of an increase in the overall amount of PrPc in the samples as discussed in the results and related to up-regulation of PrP in cells resident in the brain or due to influx of inflammatory cells either as a result of damage or the presence of a non-prion related disease. Third, that the PrP in these samples is bound to an unidentified molecule that confers higher PK resistance, or fourth, inhibits proteinase K. IBNC is likely to represent a subset of this group of cattle. Based on these data, our overall conclusion is that a second type of BSE is unlikely to have co-existed at a high prevalence with the classical form in the cattle population during the UK epidemic.
snip...see full text ;
http://randd.defra.gov.uk/Document.aspx?Document=SE1796_8548_FIN.doc
IBNC BSE TSE update ;
Tuesday, November 17, 2009 SEAC NEW RESULTS ON IDIOPATHIC BRAINSTEM NEURONAL CHROMATOLYSIS (IBNC) FROM THE VETERINARY LABORATORIES AGENCY (VLA) SEAC 103/1
http://bse-atypical.blogspot.com/2009/11/seac-new-results-on-idiopathic.html
31 March 2009 - A summary of the 102nd SEAC meeting (35 KB) held on 4th March 2009
snip...
SEAC noted that IBNC appeared to be a rare disease that occurred in older cattle, predominantly as single cases, although it is possible that surveillance may not detect all cases. Biochemical studies suggested that the prion protein may play a role in the disease. However, it is unclear whether the normal form of the protein or an abnormal form is involved. Studies are required to determine whether IBNC is transmissible or not. SEAC concluded, noting that specified risk material controls are in place to prevent cattle brain from entering the food supply, that current data on IBNC do not suggest it presents a risk to human health.
http://www.seac.gov.uk/summaries/seac102_summary.pdf
>>> All of the 15 cattle tested showed that the brains had abnormally accumulated prion protein. <<<
Saturday, February 28, 2009
NEW RESULTS ON IDIOPATHIC BRAINSTEM NEURONAL CHROMATOLYSIS "All of the 15 cattle tested showed that the brains had abnormally accumulated PrP" 2009
SEAC 102/2
http://bse-atypical.blogspot.com/2009/02/new-results-on-idiopathic-brainstem.html
Wednesday, October 08, 2008
Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?
http://bse-atypical.blogspot.com/2008/10/idiopathic-brainstem-neuronal.html
8. I was in receipt of no extra funds beyond those provided by the NHS and the University of London to run my laboratories and pay my salary as a senior lecturer/honorary Consultant and I suffered no constraints over my publications, lectures to my students, or statements to the media. However, I became increasingly aware after 1988 that questioning official dogma about BSE brought difficulties to one’s career. I was myself about to retire from the Charing Cross Hospital, where I worked as a Consultant Neuropathologist, but I observed with horror that the good reputations of dissenting scientists in the field, not least Dr Stephen Dealler and especially Dr Harash Narang were systematically undermined.
http://collections.europarchive.org/tna/20080102135133/http://www.bseinquiry.gov.uk/files/ws/s410.pdf
THEY KNEW 2 DECADES AGO the damn BSE mad cow testing were not finding cases ;
BSE-NON-CONFIRMATION OF DISEASE
3. A question posed by Mr Whaley (para 2) is that classical lesions of BSE may not occur in all cases. Supposing we had a strain variant that produced it's lesions in the cerebrum these would not be detected by our current method. I think this would be unlikely but not impossible - another reason why at least a proportion of complete brains (or blocks) should be retained during the epidemic so if the problem Mr Whaley indicates escalates, it can be investigated.
snip...
5. IF you had the information what benefit would there be ? what would you do with it ?
CONCLUSION
I do not recommend any action. The situation should be accepted. I do not think the VIS can do more at present. The situation should be kept under review particularly if there is an escalation in numbers in this category.
R BRADLEY
15 MAY 1990
90/5.15/3.2
http://collections.europarchive.org/tna/20090505194948/http://bseinquiry.gov.uk/files/yb/1990/05/15003001.pdf
''THE LINE TO TAKE'' ON IBNC $$$ 1995 $$$
1995
page 9 of 14 ;
30. The Committee noted that the results were unusual. the questioned whether there could be coincidental BSE infection or contamination with scrapie. Dr. Tyrell noted that the feeling of the committee was that this did not represent a new agent but it was important to be prepared to say something publicly about these findings. A suggested line to take was that these were scientifically unpublishable results but in line with the policy of openness they would be made publicly available and further work done to test their validity. Since the BSE precautions were applied to IBNC cases, human health was protected. Further investigations should be carried out on isolations from brains of IBNC cases with removal of the brain and subsequent handling under strict conditions to avoid the risk of any contamination.
31. Mr. Bradley informed the Committee that the CVO had informed the CMO about the IBNC results and the transmission from retina and he, like the Committee was satisfied that the controls already in place or proposed were adequate. ...
snip... see full text ;
http://collections.europarchive.org/tna/20080102204938/http://www.bseinquiry.gov.uk/files/yb/1995/06/21005001.pdf
SEAC MINUTES OF THE 19TH MEETING HELD ON 21 JUNE 1995 AT THE CENTRAL VETERINARY LABORATORY
31. Mr Bradley informed the Committee that the CVO had informed the CMO about the IBNC results and the transmission from retina and he, like the Committee was satisfied that the controls already in place or proposed were adequate. ...
http://web.archive.org/web/20030327015011/http://www.bseinquiry.gov.uk/files/yb/1995/06/21005001.pdf
ALSO, please note, atypical BSE-H strain is also transmissible in the humanized transgenic mice with distinct phenotype ;
P26
TRANSMISSION OF ATYPICAL BOVINE SPONGIFORM ENCEPHALOPATHY (BSE) IN HUMANIZED MOUSE MODELS
Liuting Qing1, Fusong Chen1, Michael Payne1, Wenquan Zou1, Cristina Casalone2, Martin Groschup3, Miroslaw Polak4, Maria Caramelli2, Pierluigi Gambetti1, Juergen Richt5*, and Qingzhong Kong1 1Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA; 2CEA, Istituto Zooprofilattico Sperimentale, Italy; 3Friedrich-Loeffler-Institut, Germany; 4National Veterinary Research Institute, Poland; 5Kansas State University, Diagnostic Medicine/Pathobiology Department, Manhattan, KS 66506, USA. *Previous address: USDA National Animal Disease Center, Ames, IA 50010, USA
Classical BSE is a world-wide prion disease in cattle, and the classical BSE strain (BSE-C) has led to over 200 cases of clinical human infection (variant CJD). Two atypical BSE strains, BSE-L (also named BASE) and BSE-H, have been discovered in three continents since 2004. The first case of naturally occurring BSE with mutated bovine PrP gene (termed BSE-M) was also found in 2006 in the USA. The transmissibility and phenotypes of these atypical BSE strains/isolates in humans were unknown. We have inoculated humanized transgenic mice with classical and atypical BSE strains (BSE-C, BSE-L, BSE-H) and the BSE-M isolate. We have found that the atypical BSE-L strain is much more virulent than the classical BSE-C. The atypical BSE-H strain is also transmissible in the humanized transgenic mice with distinct phenotype, but no transmission has been observed for the BSE-M isolate so far.
III International Symposium on THE NEW PRION BIOLOGY: BASIC SCIENCE, DIAGNOSIS AND THERAPY 2 - 4 APRIL 2009, VENEZIA (ITALY)
http://www.istitutoveneto.it/prion_09/Abstracts_09.pdf
BUT yet, USDA scientist even managed to change that science around too, by having the only cow known in the world to date that is familial BSE $ PLEASE NOTE, this so-called BSE with mutated bovine PrP gene (termed BSE-M) that was found in 2006 in the USA. a supposedly new strain of familial BSE ? takes me back to the infamous sporadic FFI, that's not familial ? they don't have a clue, in my opinion. but yet the USDA officials will blame it on anything and everything, but the most likely cause i.e. MAD COW FEED IN COMMERCE. Instead, now we have another new strain of mad cow disease, only this is in the USA, and it is just a spontaneous old cow disease i.e. 'familial h-BSEalabama'.
''We hypothesize that the bovine Prnp E211K mutation most likely has caused BSE in “the approximately 10-year-old cow” carrying the E221K mutation.''
WHAT a hoot. They have now taken the same strain of mad cow disease (h-BSE), that Kong et al in 2009 showed was transmissible to humans via human TG mice, and termed it another new mad cow disease, termed ‘‘U.S. BSE Alabama’’ as being another spontaneous happening from nothing. I swear, this just get's better and better. what about IBNC BSE, no cases yet in the USA ? and just what is IBNC BSE ? (more on that later).
BSE Case Associated with Prion Protein Gene Mutation
Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) of cattle and was first detected in 1986 in the United Kingdom. It is the most likely cause of variant Creutzfeldt-Jakob disease (CJD) in humans. The origin of BSE remains an enigma. Here we report an H-type BSE case associated with the novel mutation E211K within the prion protein gene (Prnp). Sequence analysis revealed that the animal with H-type BSE was heterozygous at Prnp nucleotides 631 through 633. An identical pathogenic mutation at the homologous codon position (E200K) in the human Prnp has been described as the most common cause of genetic CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. A recent epidemiological study revealed that the K211 allele was not detected in 6062 cattle from commercial beef processing plants and 42 cattle breeds, indicating an extremely low prevalence of the E211K variant (less than 1 in 2000) in cattle.
Author Summary Top
Bovine spongiform encephalopathy (BSE or Mad Cow Disease), a transmissible spongiform encephalopathy (TSE) or prion disease of cattle, was first discovered in the United Kingdom in 1986. BSE is most likely the cause of a human prion disease known as variant Creutzfeldt Jakob Disease (vCJD). In this study, we identified a novel mutation in the bovine prion protein gene (Prnp), called E211K, of a confirmed BSE positive cow from Alabama, United States of America. This mutation is identical to the E200K pathogenic mutation found in humans with a genetic form of CJD. This finding represents the first report of a confirmed case of BSE with a potential pathogenic mutation within the bovine Prnp gene. We hypothesize that the bovine Prnp E211K mutation most likely has caused BSE in “the approximately 10-year-old cow” carrying the E221K mutation.
http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000156
http://www.plospathogens.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.ppat.1000156&representation=PDF
WHAT does this study show. IS it really a novel mutation in the bovine prion protein gene (Prnp), called E211K, of a confirmed BSE positive cow from Alabama, United States of America, the only one in the world ?
How can scientist around the globe continue to believe such junk science coming from the ARS and USDA, and not see through all this, and still continue to want to trade with them ?
maybe I am not suppose to understand all this, or maybe they just wish I couldn't (and I am not claiming to understand all of it). I just know that something is not computing anymore with the UKBSEnvCJD theory, the rest of different atypical TSE, and the USDA and OIE only theory we are suppose to believe in. I see now where Japan and the USA are going to swap out BSE risk for FMD risk, and it's all about trade once again $ I have seen the FDA claim that feeding 5.5 grams of banned mad cow feed at the Purina plant in Gonzales Texas to each cow was not enough of the TSE agent to worry about. I have seen the TDAH and or the USDA et al completely cover up a highly suspect stumbling and staggering mad cow, sent straight to be rendered without any test at all for mad cow disease and then just claim ignorance, but we knew it was ordered from higher up officials. then we watched another mad cow in Texas, that was confirmed by a secret test to be a positive test, but yet this cow was ordered to be negative, until it took an act of Congress, and 7 months later and scientist complaining from around the globe, that this cow should be re-tested. IT was and it was CONFIRMED 7 months later. I have seen, and it was proven that part of the infamous June 2004 enhanced BSE surveillance and testing program was a sham, they were getting healthy brains from cattle they knew did not have mad cow disease and submitting them for testing. The were busted for that too. It was proven to be true. Then another 9,200 cows in the same program used a test least likely to find mad cow disease i.e. the IHC. oh yea, they did everything they could to claim the Washington cow that was positive, was not a USA cow, and in the end it worked, the suspect mad cow that was suppose to be from the USA, well that was not the right cow, it was another one, this one from Canada. after the back to back h-familial-BSE in Alabama, and h-BSE(whatever they come up with later) in Texas, right after these two cows were documented, they saw the writing on the wall and shut the testing down to numbers so low, it's now mathematically impossible to detect a mad cow case in the USA. what I have seen in these 13+ years is politics manipulate science, and it's not pretty.
The OIE and USDA et al sold there soul to the devil, and in doing so, they sold yours too.
EU IBNC BSE, ANOTHER OLD COW DISEASE, is m-BSE i.e. h-familial-BSE in Alabama only, is this EU IBNC BSE ???
OR, is this just another case of mad cow disease officials are trying to pawn off as something else $$$
Let's look at this closer.
h-familial-BSE in Alabama case
Obvious lesions of spongiform encephalopathy diagnostic for BSE were not present in the brainstem, however it was positive for the presence of PrPd by IHC (Figure 1B). Distribution of PrPd in the brainstem of this animal was not as uniform or as intense as seen with the C-type U.S. BSE case from 2003 (Figure 1C) [4]
Immunohistochemistry
Brain tissue was placed in 10% buffered formalin and after a minimum of 4 days of fixation appropriate sections of brainstem in the obex region were put in cassettes and kept in fresh formalin until they were processed for routine paraffin embedding. The procedure was described in detail previously [4]. The IHC results were interpreted as follows: (i) positive for PrPd: pink to red and (ii) background and negative for PrPd: only blue background. As positive controls, slides from the brainstem of a BSE-positive cow, obtained from the United Kingdom and from the U.S. BSE Case 2003 were used. As negative controls, slides from brainstem material of BSE-negative cattle and scrapie-negative sheep were used.
http://www.plospathogens.org/article/fetchObjectAttachment.action?uri=info%3Adoi%2F10.1371%2Fjournal.ppat.1000156&representation=PDF
IBNC BSE, that's not BSE, but is another novel prion disease.
Atypical prion proteins in cattle DEFRA project code SE1796 FOIA Final report
snip...
Investigation of the distribution and molecular characteristics of PrP from known IBNC
See also: Idiopathic Brainstem Neuronal Chromatolysis (IBNC): a novel prion protein related disorder of cattle?
Jeffrey M, Perez BB, Martin S, Terry L, González L.
BMC Vet Res. 2008 Sep 30;4:38
Further investigations demonstrated that 57% the assays performed on the confirmed IBNC samples, using the 0.3 Bio-Rad TeSeE assay (n=42), gave values above those of the test kit control and also the BSE negative brain pool control.
Half brains from six IBNC affected animals were retrieved from the TSE archive alongside the brainstem from a seventh animal. The cortex, brainstem, cerebellum and midbrain from these brains were sub-sampled and the adapted Bio-Rad TeSeE EIA, IDEXX Herdchek and Western Blot protocols applied to these tissues, in order to determine whether they could represent a form of atypical BSE. These samples had previously been found to be negative using the commercial Bio-Rad EIA and re-testing using this assay and the IDEXX Herdchek assay confirmed their negative status. When assayed using the adapted Bio-Rad protocol at 0.3µl/ml PK, 24/42 (57%) of the sample assays performed gave values above those of the test kit control and also the BSE negative brain pool control. Values above twice that of the calculated cut-off levels were found for each case but not for each brain site
No PrPres was detected when Western blotting these samples at either 20 or 4µl/ml PK but a signal was detected on the gels when blotted at the 0.12 and 0.3µl/ml PK levels. At 0.12µl/ml PK the IBNC samples were indistinguishable from the negative controls but at the 0.3µl/ml level more PrPres was detected in the IBNC cases than in the controls with each of the antibodies tested (SHA31, F99, SAF84 and P4). Illustrations of the F99 blot are shown in the paper. Other data not shown.
These data suggest that IBNC affected cattle abnormally express or accumulate PrP in brain and that the abnormal PrP is not strongly resistant to protease digestion. The results suggest that either the range of prion diseases is still wider than previously thought or that abnormalities of prion protein expression may be associated with brain lesions unconnected with prion disorders. Biochemical and transmission studies are planned in order to investigate further (under SE2014).
http://randd.defra.gov.uk/Document.aspx?Document=SE1796_8548_FIN.doc
c-BSE, atypical l-BSE, atypical h-BSE, m-BSE and or atypical familial h-BSEalabama, IBNC
just what is this IBNC and or the m-BSE in the bovine, and or could they be the same ?
are they just another strain of BSE ?
TSS
Labels: bse, familial h-type BSE, H-TYPE BSE, IBNC, L-TYPE-BSE, m-BSE
posted by Terry S. Singeltary Sr. at
4:06 PM
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