Real-time quaking-induced conversion (RT-QuIC) allows the amplification of miniscule amounts of scrapie prion protein (PrP Sc ). Recent studies applied the RT-QuIC methodol- ogy to cerebrospinal fluid (CSF) for diagnosing human prion diseases. However, to date, there has not been a formal multi- centre assessment of the reproducibility, validity and stability of RT-QuIC in this context, an indispensable step for establish- ment as a diagnostic test in clinical practice. In the present study, we analysed CSF from 110 prion disease patients and 400 control patients using the RT-QuIC method under various conditions. In addition, "blinded" ring trials between different participating sites were performed to estimate reproducibility. Using the previously established cut-off of 10,000 relative fluo- rescence units (rfu), we obtained a sensitivity of 85 % and a specificity of 99 %. The multi-centre inter-laboratory reproduc- ibility of RT-QuIC revealed a Fleiss'kappa value of 0.83 (95 % CI: 0.40-1.00) indicating an almost perfect agreement. More- over, we investigated the impact of short-term CSF storage at different temperatures, long-term storage, repeated freezing and thawing cycles and the contamination of CSF with blood on the RT-QuIC seeding response. Our data indicated that the PrP Sc seed in CSF is stable to any type of storage condition but sensitive to contaminations with blood (>1250 erythrocytes/ μL), which results in a false negative RT-QuIC response. Fresh blood-contaminated samples (3 days)can be rescued by remov- al of erythrocytes. The present study underlines the reproduc- ibility and high stability of RT-QuIC across various CSF stor- age conditions with a remarkable sensitivity and specificity, suggesting RT-QuIC as an innovative and robust diagnostic method.

/pdf/stability-and-reproducibility-underscore-utility-of-rt-quic-5abboblnt7.pdf

Stability and Reproducibility Underscore Utility of RT-QuIC for Diagnosis of Creutzfeldt-Jakob Disease.

Current ante-mortem techniques for diagnosis of bovine tuberculosis.

Multiple neurodegenerative diseases are characterized by aggregation of tau molecules. Adult humans express six isoforms of tau that contain either 3 or 4 microtubule binding repeats (3R or 4R tau). Different diseases involve preferential aggregation of 3R (e.g Pick disease), 4R (e.g. progressive supranuclear palsy), or both 3R and 4R tau molecules [e.g. Alzheimer disease and chronic traumatic encephalopathy]. Three ultrasensitive cell-free seed amplification assays [called tau real-time quaking induced conversion (tau RT-QuIC) assays] have been developed that preferentially detect 3R, 4R, or 3R/4R tau aggregates in biospecimens. In these reactions, low-fg amounts of a given self-propagating protein aggregate (the seed) are incubated with a vast excess of recombinant tau monomers (the substrate) in multi-well plates. Over time, the seeds incorporate the substrate to grow into amyloids that can then be detected using thioflavin T fluorescence. Here we describe a tau RT-QuIC assay (K12 RT-QuIC) that, using a C-terminally extended recombinant 3R tau substrate (K12CFh), enables sensitive detection of Pick disease, Alzheimer disease, and chronic traumatic encephalopathy seeds in brain homogenates. The discrimination of Pick disease from Alzheimer disease and chronic traumatic encephalopathy cases is then achieved through the quantitative differences in K12 RT-QuIC assay thioflavin T responses, which correlate with structural properties of the reaction products. In particular, Fourier transform infrared spectroscopy analysis of the respective K12CFh amyloids showed distinct β-sheet conformations, suggesting at least partial propagation of the original seed conformations in vitro. Thus, K12 RT-QuIC provides a single assay for ultrasensitive detection and discrimination of tau aggregates comprised mainly of 3R, or both 3R and 4R, tau isoforms.

/pdf/a-single-ultrasensitive-assay-for-detection-and-3zyjga0np6.pdf

A single ultrasensitive assay for detection and discrimination of tau aggregates of Alzheimer and Pick diseases

Chronic wasting disease (CWD) is a prion disease of captive and free-ranging deer (Odocoileus spp), elk (Cervus elaphus nelsonii) and moose (Alces alces shirasi). Unlike in most other prion diseases, in CWD prions are shed in urine and feces, which most likely contributes to the horizontal transmission within and between cervid species. To date, CWD ante-mortem diagnosis is only possible by immunohistochemical detection of protease resistant prion protein (PrPSc) in tonsil or recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsies, which requires anesthesia of animals. We report on detection of CWD prions in urine collected from pre-symptomatic deer and in fecal extracts by using real time quaking-induced conversion (RT-QuIC). This assay can be useful for non-invasive pre-symptomatic diagnosis and surveillance of CWD.

Early detection of chronic wasting disease prions in urine of pre-symptomatic deer by real-time quaking-induced conversion assay.

Bovine tuberculosis, caused by Mycobacterium bovis, is a zoonotic disease of international public health importance. Ante-mortem surveillance is essential for control; however, current surveillance tests are hampered by limitations affecting ease of use or quality of results. There is an emerging interest in human and veterinary medicine in diagnosing disease via identification of volatile organic compounds produced by pathogens and host-pathogen interactions. The objective of this pilot study was to explore application of existing human breath collection and analysis methodologies to cattle as a means to identify M. bovis infection through detection of unique volatile organic compounds or changes in the volatile organic compound profiles present in breath. Breath samples from 23 male Holstein calves (7 non-infected and 16 M. bovis-infected) were collected onto commercially available sorbent cartridges using a mask system at 90 days post-inoculation with M. bovis. Samples were analyzed using gas chromatography-mass spectrometry, and chromatographic data were analyzed using standard analytical chemical and metabolomic analyses, principle components analysis, and a linear discriminant algorithm. The findings provide proof of concept that breath-derived volatile organic compound analysis can be used to differentiate between healthy and M. bovis-infected cattle.

/pdf/a-pilot-study-exploring-the-use-of-breath-analysis-to-22ptputpzu.pdf

A pilot study exploring the use of breath analysis to differentiate healthy cattle from cattle experimentally infected with Mycobacterium bovis.

Currently, the Bovigam assay is used as an official supplemental test within bovine tuberculosis control programs. The objectives of the present study were to evaluate two Mycobacterium bovis-specific peptide cocktails and purified protein derivatives (PPDs) from two sources, liquid and lyophilized antigen preparations. PPDs and peptide cocktails were also used for comparison of a second-generation gamma interferon (IFN-γ) release assay kit with the currently licensed first-generation kit (Bovigam; Prionics AG). Three strains of M. bovis were used for experimental challenge: M. bovis 95-1315, M. bovis Ravenel, and M. bovis 10-7428. Additionally, samples from a tuberculosis-affected herd (i.e., naturally infected) were evaluated. Robust responses to both peptide cocktails, HP (PC-HP) and ESAT-6/CFP10 (PC-EC), and the PPDs were elicited as early as 3 weeks after challenge. Only minor differences in responses to Commonwealth Serum Laboratories (CSL) and Lelystad PPDs were detected with samples from experimentally infected animals. For instance, responses to Lelystad M. avium-derived PPD (PPDa) exceeded the respective responses to the CSL PPDa in M. bovis Ravenel-infected and control animals. However, a 1:4 dilution of stimulated plasma demonstrated greater separation of PPDb from PPDa responses (i.e., PPDb minus PPDa) with the use of Lelystad PPDs, suggesting that Lelystad PPDs provide greater diagnostic sensitivity than CSL PPDs. The responses to lyophilized and liquid antigen preparations did not differ. Responses detected with first- and second-generation IFN-γ release assay kits (Bovigam) did not differ throughout the study. In conclusion, antigens may be stored in a lyophilized state without loss in potency, PC-HP and PC-EC are dependable biomarkers for aiding in the detection of bovine tuberculosis, and second-generation Bovigam kits are comparable to currently used kits.

https://cvi.asm.org/content/cdli/20/12/1827.full.pdf

Clinical and diagnostic developments of a gamma interferon release assay for use in bovine tuberculosis control programs.

A prion disease blood test using immunoprecipitation and enhanced quaking-induced conversion.

Clinical and Diagnostic Developments of a Gamma Interferon Release Assay (Bovigam

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Clinical and diagnostic developments of a gamma interferon release assay for use in bovine tuberculosis control programs.

A prion disease blood test using immunoprecipitation and enhanced quaking-induced conversion.

Clinical and Diagnostic Developments of a Gamma Interferon Release Assay (Bovigam