A highly specific blood test for vCJD Jackson, Graham S.; Burk-Rafel, Jesse; Edgeworth, Julie A. ...
Blood,
01/2014, Letnik:
123, Številka:
3
Journal Article
Spontaneous generation of mammalian prions Edgeworth, Julie A.; Gros, Nathalie; Alden, Jack ...
Proceedings of the National Academy of Sciences - PNAS,
08/2010, Letnik:
107, Številka:
32
Journal Article
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Prions are transmissible agents that cause lethal neurodegeneration in humans and other mammals. Prions bind avidly to metal surfaces such as steel wires and, when surface-bound, can initiate ...infection of brain or cultured cells with remarkable efficiency. While investigating the properties of metal-bound prions by using the scrapie cell assay to measure infectivity, we observed, at low frequency, positive assay results in control groups in which metal wires had been coated with uninfected mouse brain homogenate. This phenomenon proved to be reproducible in rigorous and exhaustive control experiments designed to exclude prion contamination. The infectivity generated in cell culture could be readily transferred to mice and had strain characteristics distinct from the mouse-adapted prion strains used in the laboratory. The apparent "spontaneous generation" of prions from normal brain tissue could result if the metal surface, possibly with bound cofactors, catalyzed de novo formation of prions from normal cellular prion protein. Alternatively, if prions were naturally present in the brain at levels not detectable by conventional methods, metal surfaces might concentrate them to the extent that they become quantifiable by the scrapie cell assay.
According to the protein-only hypothesis, infectious mammalian prions, which exist as distinct strains with discrete biological properties, consist of multichain assemblies of misfolded cellular ...prion protein (PrP). A critical test would be to produce prion strains synthetically from defined components. Crucially, high-titre ‘synthetic' prions could then be used to determine the structural basis of infectivity and strain diversity at the atomic level. While there have been multiple reports of production of prions from bacterially expressed recombinant PrP using various methods, systematic production of high-titre material in a form suitable for structural analysis remains a key goal. Here, we report a novel high-throughput strategy for exploring a matrix of conditions, additives and potential cofactors that might generate high-titre prions from recombinant mouse PrP, with screening for infectivity using a sensitive automated cell-based bioassay. Overall, approximately 20 000 unique conditions were examined. While some resulted in apparently infected cell cultures, this was transient and not reproducible. We also adapted published methods that reported production of synthetic prions from recombinant hamster PrP, but again did not find evidence of significant infectious titre when using recombinant mouse PrP as substrate. Collectively, our findings are consistent with the formation of prion infectivity from recombinant mouse PrP being a rare stochastic event and we conclude that systematic generation of prions from recombinant PrP may only become possible once the detailed structure of authentic ex vivo prions is solved.
Summary Background Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative disorder originating from exposure to bovine-spongiform-encephalopathy-like prions. Prion infections are ...associated with long and clinically silent incubations. The number of asymptomatic individuals with vCJD prion infection is unknown, posing risk to others via blood transfusion, blood products, organ or tissue grafts, and contaminated medical instruments. We aimed to establish the sensitivity and specificity of a blood-based assay for detection of vCJD prion infection. Methods We developed a solid-state binding matrix to capture and concentrate disease-associated prion proteins and coupled this method to direct immunodetection of surface-bound material. Quantitative assay sensitivity was assessed with a serial dilution series of 10−7 to 10−10 of vCJD prion-infected brain homogenate into whole human blood, with a baseline control of normal human brain homogenate in whole blood (10−6 ). To establish the sensitivity and specificity of the assay for detection of endogenous vCJD, we analysed a masked panel of 190 whole blood samples from 21 patients with vCJD, 27 with sporadic CJD, 42 with other neurological diseases, and 100 normal controls. Samples were masked and numbered by individuals independent of the assay and analysis. Each sample was tested twice in independent assay runs; only samples that were reactive in both runs were scored as positive overall. Findings We were able to distinguish a 10−10 dilution of exogenous vCJD prion-infected brain from a 10−6 dilution of normal brain (mean chemiluminescent signal, 1·3×105 SD 1·1×104 for vCJD vs 9·9×104 4·5×103 for normal brain; p<0·0001)—an assay sensitivity that was orders of magnitude higher than any previously reported. 15 samples in the masked panel were scored as positive. All 15 samples were from patients with vCJD, showing an assay sensitivity for vCJD of 71·4% (95% CI 47·8–88·7) and a specificity of 100% (95% CIs between 97·8% and 100%). Interpretation These initial studies provide a prototype blood test for diagnosis of vCJD in symptomatic individuals, which could allow development of large-scale screening tests for asymptomatic vCJD prion infection. Funding UK Medical Research Council.
Objective To assess the cost effectiveness of screening, isolation, and decolonisation strategies in the control of meticillin resistant Staphylococcus aureus (MRSA) in intensive care units.Design ...Economic evaluation based on a dynamic transmission model.Setting England and Wales.Population Theoretical population of patients on an intensive care unit.Main outcome measures Infections, deaths, costs, quality adjusted life years (QALYs), incremental cost effectiveness ratios for alternative strategies, and net monetary benefits.Results All decolonisation strategies improved health outcomes and reduced costs. Although universal decolonisation (regardless of MRSA status) was the most cost effective in the short term, strategies using screening to target MRSA carriers may be preferred owing to the reduced risk of selecting for resistance. Among such targeted strategies, universal admission and weekly screening with polymerase chain reaction coupled with decolonisation using nasal mupirocin was the most cost effective. This finding was robust to the size of intensive care units, prevalence of MRSA on admission, proportion of patients classified as high risk, and precise value of willingness to pay for health benefits. All strategies using isolation but not decolonisation improved health outcomes but costs were increased. When the prevalence of MRSA on admission to the intensive care unit was 5% and the willingness to pay per QALY gained was between £20 000 (€23 000; $32 000) and £30 000, the best such strategy was to isolate only those patients at high risk of carrying MRSA (either pre-emptively or after identification by admission and weekly screening for MRSA using chromogenic agar). Universal admission and weekly screening using polymerase chain reaction based detection of MRSA coupled with isolation was unlikely to be cost effective unless prevalence was high (10% of patients colonised with MRSA on admission).Conclusions MRSA control strategies that use decolonisation are likely to be cost saving in an intensive care unit setting provided resistance is lacking, and combining universal screening using polymerase chain reaction with decolonisation is likely to represent good value for money if untargeted decolonisation is considered unacceptable. In intensive care units where decolonisation is not implemented, evidence is insufficient to support universal screening for MRSA outside high prevalence settings.
Improved understanding and management of COVID-19, a potentially life-threatening disease, could greatly reduce the threat posed by its etiologic agent, SARS-CoV-2. Toward this end, we have ...identified a core peripheral blood immune signature across 63 hospital-treated patients with COVID-19 who were otherwise highly heterogeneous. The signature includes discrete changes in B and myelomonocytic cell composition, profoundly altered T cell phenotypes, selective cytokine/chemokine upregulation and SARS-CoV-2-specific antibodies. Some signature traits identify links with other settings of immunoprotection and immunopathology; others, including basophil and plasmacytoid dendritic cell depletion, correlate strongly with disease severity; while a third set of traits, including a triad of IP-10, interleukin-10 and interleukin-6, anticipate subsequent clinical progression. Hence, contingent upon independent validation in other COVID-19 cohorts, individual traits within this signature may collectively and individually guide treatment options; offer insights into COVID-19 pathogenesis; and aid early, risk-based patient stratification that is particularly beneficial in phasic diseases such as COVID-19.
Epidemiological and whole-genome sequencing analysis of an ongoing outbreak of Streptococcus pyogenes (Group A Streptococcus) in London (United Kingdom).
Prospective identification of Group A ...Streptococcus cases from a diagnostic laboratory serving central and south London between 27 November and 10 December 2022. Case notes were reviewed and isolates were retrieved. Case numbers were compared with the previous 5 years. Whole-genome sequencing was performed with long-read, nanopore technology for emm typing and identification of superantigen genes. Associations of pathogen-related factors with an invasive disease were assessed by single-variable and multi-variable logistic regression.
Case numbers began increasing in October 2022 from a baseline of 2.0 cases per day, and in December 2022, the average daily case numbers reached 10.8 cases per day, four-fold the number usually seen in winter. A total of 113 cases were identified during the prospective study period. Three quarters (86/113, 76%) were paediatric cases, including 2 deaths. Of 113 cases, 11 (10%) were invasive. In total, 56 isolates were successfully sequenced, including 10 of 11 (91%) invasive isolates. The emm12 (33/56, 59%) and emm1 (9/56, 16%) types were predominant, with 7 of 9 (78%) emm1 isolates being from the M1uk clone. The majority of invasive isolates had superantigen genes spea (7/10, 70%) and spej (8/10, 80%), whereas, in non-invasive isolates, these superantigen genes were found less frequently (spea: 5/46, 11% and spej: 7/46, 15%). By multivariable analysis of pathogen-related factors, spea (OR 8.9, CI 1.4–57, p 0.020) and spej (OR 12, CI 1.8–78, p 0.011) were associated with invasive disease.
emm12 and emm1 types predominate in the ongoing outbreak, which mainly affects children. In this outbreak, the spea and spej superantigen genes are associated with the severity of presentation.
We demonstrate the reproducible fabrication of single‐walled carbon nanotube (SWNT) networks, via catalyzed chemical vapor deposition (cCVD). Fe nanoparticles are employed as the catalyst, with ...methane as the carbon‐containing gas. cCVD growth under these conditions results in the formation of multiply interconnected, random, two‐dimensional networks of SWNTs. Investigation of the effect of parameters such as methane flow rate and temperature on the growth process enables control over the density of the network, which controls the network conductivity. Low‐density networks demonstrate p‐type semiconductor behavior, whilst high‐density networks exhibit semimetallic behavior. In both cases conductance is demonstrated over macroscopic length scales, up to millimeters, much longer than the individual SWNTs, despite the surface coverage being <1 %. The networks can be defined in regions of a surface by photolithography before or after growth. Controlled growth of SWNT networks thus enables the application of SWNTs as macroscale conductors with controllable, predictable, and reproducible characteristics.
Multiply interconnected, random, 2D networks of single‐walled carbon nanotubes (SWNTs) are formed by chemical vapor deposition. The networks conduct over macroscopic length scales despite the surface coverage being <1 %, they can be patterned on a surface (see image), and they behave like p‐type semiconductors at low density or as semimetals at high density. Controlled growth of SWNT networks enables their application as macroscale conductors with controllable, predictable, and reproducible characteristics.
Studies estimating excess length of stay (LOS) attributable to nosocomial infections have failed to address time-varying confounding, likely leading to overestimation of their impact. We present a ...methodology based on inverse probability-weighted survival curves to address this limitation.
A case study focusing on intensive care unit-acquired bacteremia using data from 2 general intensive care units (ICUs) from 2 London teaching hospitals were used to illustrate the methodology. The area under the curve of a conventional Kaplan-Meier curve applied to the observed data was compared with that of an inverse probability-weighted Kaplan-Meier curve applied after treating bacteremia as censoring events. Weights were based on the daily probability of acquiring bacteremia. The difference between the observed average LOS and the average LOS that would be observed if all bacteremia cases could be prevented was multiplied by the number of admitted patients to obtain the total excess LOS.
The estimated total number of extra ICU days caused by 666 bacteremia cases was estimated at 2453 (95% confidence interval CI, 1803-3103) days. The excess number of days was overestimated when ignoring time-varying confounding (2845 95% CI, 2276-3415) or when completely ignoring confounding (2838 95% CI, 2101-3575).
ICU-acquired bacteremia was associated with a substantial excess LOS. Wider adoption of inverse probability-weighted survival curves or alternative techniques that address time-varying confounding could lead to better informed decision making around nosocomial infections and other time-dependent exposures.
A cCVD method for producing transparent, conducting carbon nanotube (CNT) mats of near complete surface coverage is described. Disk‐shaped UMEs using the CNT mats reveal reversible electrochemistry ...for outer sphere redox species and remarkably low capacitance. CNT mat UMEs can be used for the electrochemical detection of dopamine at micromole concentrations in albumin solution, with no decrease in electrode performance even after extensive use.
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