B Cells and Platelets Harbor Prion Infectivity in the Blood of Deer Infected with Chronic Wasting Disease

Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
Journal of Virology (Impact Factor: 4.44). 03/2010; 84(10):5097-107. DOI: 10.1128/JVI.02169-09
Source: PubMed


Substantial evidence for prion transmission via blood transfusion exists for many transmissible spongiform encephalopathy
(TSE) diseases. Determining which cell phenotype(s) is responsible for trafficking infectivity has important implications
for our understanding of the dissemination of prions, as well as their detection and elimination from blood products. We used
bioassay studies of native white-tailed deer and transgenic cervidized mice to determine (i) if chronic wasting disease (CWD)
blood infectivity is associated with the cellular versus the cell-free/plasma fraction of blood and (ii) in particular if
B-cell (MAb 2-104+), platelet (CD41/61+), or CD14+ monocyte blood cell phenotypes harbor infectious prions. All four deer transfused with the blood mononuclear cell fraction
from CWD+ donor deer became PrPCWD positive by 19 months postinoculation, whereas none of the four deer inoculated with cell-free plasma from the same source
developed prion infection. All four of the deer injected with B cells and three of four deer receiving platelets from CWD+ donor deer became PrPCWD positive in as little as 6 months postinoculation, whereas none of the four deer receiving blood CD14+ monocytes developed evidence of CWD infection (immunohistochemistry and Western blot analysis) after 19 months of observation.
Results of the Tg(CerPrP) mouse bioassays mirrored those of the native cervid host. These results indicate that CWD blood
infectivity is cell associated and suggest a significant role for B cells and platelets in trafficking CWD infectivity in vivo and support earlier tissue-based studies associating putative follicular B cells with PrPCWD. Localization of CWD infectivity with leukocyte subpopulations may aid in enhancing the sensitivity of blood-based diagnostic
assays for CWD and other TSEs.

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Available from: Candace K Mathiason
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    • "The contribution of plasma to blood infectivity also depends on the experimental paradigm. In rodents, up to fifty percent of blood infectivity is recovered from plasma [18] while plasma does not seem to be infectious in cervids [16]. In sheep, plasma is consistently infectious albeit less than whole blood [20]. "
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    ABSTRACT: Prion transmission can occur by blood transfusion in human variant Creutzfeldt-Jakob disease and in experimental animal models, including sheep. Screening of blood and its derivatives for the presence of prions became therefore a major public health issue. As infectious titer in blood is reportedly low, highly sensitive and robust methods are required to detect prions in blood and blood derived products. The objectives of this study were to compare different methods - in vitro, ex vivo and in vivo assays - to detect prion infectivity in cells prepared from blood samples obtained from scrapie infected sheep at different time points of the disease. Protein misfolding cyclic amplification (PMCA) and bioassays in transgenic mice expressing the ovine prion protein were the most efficient methods to identify infected animals at any time of the disease (asymptomatic to terminally-ill stages). However scrapie cell and cerebellar organotypic slice culture assays designed to replicate ovine prions in culture also allowed detection of prion infectivity in blood cells from asymptomatic sheep. These findings confirm that white blood cells are appropriate targets for preclinical detection and introduce ex vivo tools to detect blood infectivity during the asymptomatic stage of the disease.
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    • "urine and feces, saliva, environmental fomites, blood or blood components, or brain tissue) and by various routes (e.g. orally, intravenously, intracranially, or through environmental exposure) [31–33]. The sources of inoculum included terminally-ill white-tailed or mule deer (Odocoileus hemionus) of unknown PrP genotype (courtesy of Michael Miller, Colorado Division of Parks and Wildlife; Terry Spraker, Colorado State University; the National Park Service; and the Wisconsin Department of Natural Resources), and sub-passage studies in white-tailed deer of either of two genotypes: homozygous for glycine (i.e. "
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    ABSTRACT: Transmissible spongiform encephalopathies (TSEs), or prion diseases, are a uniformly fatal family of neurodegenerative diseases in mammals that includes chronic wasting disease (CWD) of cervids. The early and ante-mortem identification of TSE-infected individuals using conventional western blotting or immunohistochemistry (IHC) has proven difficult, as the levels of infectious prions in readily obtainable samples, including blood and bodily fluids, are typically beyond the limits of detection. The development of amplification-based seeding assays has been instrumental in the detection of low levels of infectious prions in clinical samples. In the present study, we evaluated the cerebrospinal fluid (CSF) of CWD-exposed (n=44) and naïve (n=4) deer (n=48 total) for CWD prions (PrP(d)) using two amplification assays: serial protein misfolding cyclic amplification with polytetrafluoroethylene beads (sPMCAb) and real-time quaking induced conversion (RT-QuIC) employing a truncated Syrian hamster recombinant protein substrate. Samples were evaluated blindly in parallel with appropriate positive and negative controls. Results from amplification assays were compared to one another and to obex immunohistochemistry, and were correlated to available clinical histories including CWD inoculum source (e.g. saliva, blood), genotype, survival period, and duration of clinical signs. We found that both sPMCAb and RT-QuIC were capable of amplifying CWD prions from cervid CSF, and results correlated well with one another. Prion seeding activity in either assay was observed in approximately 50% of deer with PrP(d) detected by IHC in the obex region of the brain. Important predictors of amplification included duration of clinical signs and time of first tonsil biopsy positive results, and ultimately the levels of PrP(d) identified in the obex by IHC. Based on our findings, we expect that both sPMCAb and RT-QuIC may prove to be useful detection assays for the detection of prions in CSF.
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    • "Our results indicate that, in the PG127 scrapie model, plasma displayed limited capacity to transmit the disease by transfusion. This observation concurs with the results recently reported in both BSE infected sheep and Chronic Wasting Diseases infected cervids [24], [36]. The results also support the view that leuco-depletion filters further reduce the risk of transmitting TSE by plasma. "
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