In vitro Detection of Prions in Blood
At A Glance
Researchers at Colorado State University have patented new techniques and methodologies to improve the sensitivity and specificity of prior amplification and detection techniques, while maintaining fast, sensitive and consistent assays for the detection of blood-borne prions.
Consistent and reliable results indicate detection of blood-borne prions in whole blood from prion-infected preclinical white-tailed deer, muntjac deer, and Syrian hamsters, attain sensitivity of >90% while maintaining 100% specificity.
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Blood-borne transmission of infectious prions during the asymptomatic or pre-clinical stage of disease occurs for both human and animal transmissible spongiform encephalopathies (TSEs). The geographical distribution of the cervid TSE (chronic wasting disease (CWD)) continues to spread across North America and the prospective number of individuals harboring an asymptomatic infection of human variant Creutzfeldt-Jakob Disease (vCJD) in the United Kingdom continues to climb.
Variant Creutzfeldt-Jakob disease (vCJD) emerged following the bovine spongiform encephalopathy (BSE) epidemic in the United Kingdom in the 1980s and 90s. Biochemical and strain typing analysis have provided evidence indicating that vCJD originated from human exposure to BSE contaminated material. To date, 225 cases of vCJD have been diagnosed worldwide, four of which have been transmitted by non-leucodepleted blood transfusion. While leucocyte reduction has been implemented to filter prions and prion carrying cells from blood products, current filtration methodologies are unable to remove 100% of TSE infectivity. In addition, recent reports have revealed that approximately 1 in 3000 residents in the United Kingdom may be asymptomatic carriers of vCJD as a result of the BSE epidemic. Thus, concern exists that a secondary outbreak of vCJD may ensue involving blood-borne prion transmission originating from individuals unknowingly carrying a subclinical prion infection.
While traditional assays, such as Western blot and immunohistochemistry (IHC), are effective for detecting large quantities of prions present in nervous and lymphoid tissue, they do not have the ability to detect the minute quantities thought to be present in bodily fluids or peripheral tissues early in infection. Rodent bioassays have the necessary sensitivity and specificity to detect hematogenous prions, but they are not realistic as rapid and cost-effective diagnostic tools.
In vitro prion detection was advanced with the advent of serial protein misfolding cyclic amplification (sPMCA). sPMCA requires less time than bioassay, but has been hampered by a lack of consistent sensitivity and a dependence on protease digestion prior to immunoassay readout. In contrast, the real-time quaking-induced conversion (RT-QuIC) assay relies upon the seeded conversion of recombinant prion protein (rPrP) to PrPD and subsequent binding of thioflavin T (ThT) to the resulting amyloid isoforms, thus offering enhanced ante-mortem prion detection and real-time fluorescence readout. However, improvement in the sensitivity and specificity of RT-QuIC would be very desirable.
- No other test for prions in blood currently exist
Luk CC, et al. Creutzfeldt-Jakob disease in pregnancy: the use of modified RT-QuIC to determine infectivity in placental tissues. Prion. 2021 Dec;15(1):107-111. doi: 10.1080/19336896.2021.1933872.PMID: 34132175
McNulty EE, Nalls AV, Xun R, Denkers ND, Hoover EA, Mathiason CK. “In vitro detection of haematogenous prions in white-tailed deer orally dosed with low concentrations of chronic wasting disease.” J Gen Virol. 2020 Mar; 101(3):347-361. doi: 10.1099/jgv.0.001367. PMID:31846418
Elder AM, Henderson DM, Nalls AV, Hoover EA, Kincaid AE, Bartz JC, Mathiason CK. Immediate and Ongoing Detection of Prions in the Blood of Hamsters and Deer following Oral, Nasal, or Blood Inoculations. J Virol. 2015 Jul;89(14):7421-4. doi: 10.1128/JVI.00760-15. PMID: 25926635; PMCID: PMC4473550.
Elder, Alan M., et al. “In Vitro Detection of Prionemia in TSE-Infected Cervids and Hamsters.” PLOS ONE, Public Library of Science, 2013, journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0080203.
Haley, Nicholas J, et al. “Prion-Seeding Activity in Cerebrospinal Fluid of Deer with Chronic Wasting Disease.” PloS One, Public Library of Science, 25 Nov. 2013, www.ncbi.nlm.nih.gov/pubmed/24282599.
Last updated: April 2022