Continuous false positive results by SARS-CoV-2 rapid antigen testing: a case report

Efficient and rapid identification of active SARS-CoV-2 infections has been key to monitoring and mitigating the spread of the virus. The implementation of nucleic acid testing (e.g., RT-PCR) was broadly adopted by most public health organizations at the national and community levels across the globe, which was followed by more accessible means of home testing including lateral flow immunochromatographic assay (LFA), also known as a rapid antigen test. Here we report the case of an adult female who repeatedly and consecutively tested positive by RAT (BTNX inc). This sustained false positive was not linked with an active SARS-CoV-2 infection, which was ruled out by RT-PCR and serological analyses. SARS-CoV-2 serology revealed no detectable levels of antibodies against the nucleocapsid suggesting no recent prior infection by SARS-CoV-2. This continuous false positive was limited to BTNX testing devices. This case report aims to describe that such continuous false positives can occur and describes alternative testing approaches that can be performed to confirm RAT results. In addition, broader awareness of such occurrences is warranted in the healthcare and public health community to avoid unnecessary negative impacts on individual’s day to day life

Mutational comparison of the single-domained APOBEC3C and double-domained APOBEC3F/G anti-retroviral cytidine deaminases provides insight into their DNA target site specificities

Human APOBEC3F and APOBEC3G are double-domained deaminases that can catalyze dC→dU deamination in HIV-1 and MLV retroviral DNA replication intermediates, targeting T–C or C–C dinucleotides, respectively. HIV-1 antagonizes their action through its vif gene product, which has been shown (at least in the case of APOBEC3G) to interact with the N-terminal domain of the deaminase, triggering its degradation. Here, we compare APOBEC3F and APOBEC3G to APOBEC3C, a single-domained deaminase that can also act on both HIV-1 and MLV. We find that whereas APOBEC3C contains all the information necessary for both Vif-binding and cytidine deaminase activity in a single domain, it is the C-terminal domain of APOBEC3F and APOBEC3G that confer their target site specificity for cytidine deamination. We have exploited the fact that APOBEC3C, whilst highly homologous to the C-terminal domain of APOBEC3F, exhibits a distinct target site specificity (preferring Y–C dinucleotides) in order to identify residues in APOBEC3F that might affect its target site specificity. We find that this specificity can be altered by single amino acid substitutions at several distinct positions, suggesting that the strong dependence of APOBEC3-mediated deoxycytidine deamination on the 5′-flanking nucleotide is sensitive to relatively subtle changes in the APOBEC3 structure. The approach has allowed the isolation of APOBEC3 DNA mutators that exhibit novel target site preferences

Circulating extracellular vesicles during pregnancy in women with type 1 diabetes: a secondary analysis of the CONCEPTT trial.

BACKGROUND: Extracellular vesicles are membrane vesicles that are released into the extracellular environment and accumulate in the circulation in vascular disease. We aimed to quantify circulating extracellular vesicles in pregnant women with type 1 diabetes and to examine associations between extracellular vesicle levels, continuous glucose measures, and pregnancy outcomes. METHODS: We used plasma samples from the Continuous Glucose Monitoring in Women with Type 1 Diabetes in Pregnancy Trial study and quantified circulating extracellular vesicles by flow cytometry (n = 163). Relationships with clinical variables were assessed by repeated measures correlation. Logistic regression was used to assess associations between elevated extracellular vesicle levels and pregnancy outcomes. RESULTS: Platelet extracellular vesicle levels were inversely associated with glucose time above range and glycaemic variability measures (P < 0.05). A weak positive association was observed between endothelial extracellular vesicles and mean amplitude of glycemic excursion (P < 0.05). In a univariate logistic regression model, high baseline endothelial extracellular vesicles was associated with increased risk of neonatal intensive care unit (NICU) admission (OR: 2.06, 1.03-4.10), and respiratory distress requiring ventilation (OR: 4.98, 1.04-23.92). After adjusting for HbA1c and blood pressure the relationship for NICU admission persisted and an association with hyperbilirubinemia was seen (OR: 2.56, 1.10-5.94). Elevated platelet extracellular vesicles were associated with an increased risk of NICU admission (OR: 2.18, 1.04-4.57), and hyperbilirubinemia (OR: 2.61, 1.11-6.12) after adjusting for HbA1c and blood pressure. CONCLUSIONS: High levels of extracellular vesicles in early pregnancy were associated with adverse neonatal outcomes. Assessment of extracellular vesicles may represent a novel approach to personalized care in type 1 diabetes pregnancy

Étude de la marqueterie d’un secrétaire à gradin du xviiie siècle

Le secrétaire à gradin (inv. V4081) conservé au musée du Louvre a fait l’objet d’une restauration en 2013 dans les ateliers du Centre de recherche et de restauration des musées de France (C2RMF), au pavillon de Flore. L’intervention s’est accompagnée d’une importante étude matérielle de la partie polychromée de la marqueterie. Les procédés de mise en œuvre de la couche picturale et de la couche de corne qui la protège ont nécessité d’adapter la méthodologie par le couplage de multiples techniques d’examens et d’analyses. Le recoupement de l’ensemble des données a permis de caractériser finement les matériaux utilisés pour deux interventions distinctes de polychromies et de mieux cerner les dates de leur mise en œuvre.The Louvre’s drop-front secretary desk with drawers (inv. V4081) was restored in 2013 in the workshops of the Centre de Recherche et de Restauration des Musées de France (C2RMF), in the Pavillon de Flore. The restoration went hand in hand with a detailed material study of the polychromed part of the marquetry. The manner of applying the layer of pigment and the veneer of horn that protected it required the methodology to be adapted through the interaction of multiple tests and analysis techniques. By cross-referencing all the data obtained, the materials used for the two separate polychromy procedures were distinguished and dated more precisely

Towards defining reference materials for extracellular vesicle size, concentration, refractive index and epitope abundance

Accurate characterization of extracellular vesicles (EVs) is critical to explore their diagnostic and therapeutic applications. As the EV research field has developed, so too have the techniques used to characterize them. The development of reference materials is required for the standardization of these techniques. This work, initiated from the ISEV 2017 Biomarker Workshop in Birmingham, UK, and with further discussion during the ISEV 2019 Standardization Workshop in Ghent, Belgium, sets out to elucidate which reference materials are required and which are currently available to standardize commonly used analysis platforms for characterizing EV size, concentration, refractive index, and epitope expression. Due to their predominant use, a particular focus is placed on the optical methods nanoparticle tracking analysis and flow cytometry.Comment: 30 pages, 6 figures, 2 table

RNA-based gene therapies for myotonic dystrophy type 1

Tableau d’honneur de la Faculté des études supérieures et postdoctorales 2003-2004La dystrophie myotonique de type 1 (DM1) est une maladie neuromusculaire grave qui engendre une perte d’autonomie des patients et diminue leur espérance de vie. Cette maladie est la plus fréquente des dystrophies musculaires chez l’adulte avec une incidence mondiale d’une personne atteinte sur 15 000. Au Québec, cette maladie est d’une importance particulière, car elle touche une personne sur 500 dans les régions du Saguenay et de Charlevoix. La DM1 est causée par l’expansion du triplet CTG situé dans la région 3’ non-codante de la myotonine protéine kinase (DMPK). Toutefois, il a été démontré que la grande part des symptômes de la maladie seraient liés à l’accumulation nucléaire de l’ARNm de DMPK portant l’expansion. Ces ARNm mutés se lient à des facteurs nucléaires formant des foci dans les noyaux des cellules DM1, engendrant des effets toxiques sur le métabolisme cellulaire et sur l’épissage alternatif de certains ARNm. Nos travaux avaient comme but premier d’évaluer si la destruction de l’ARNm mutant de DMPK dans des myoblastes provenant de muscle squelettique DM1 permettrait de rétablir certaines fonctions et caractéristiques normales dans ces cellules. Trois technologies à base d’ARNs: les antisens, les ribozymes et les shRNAs ont diminué avec succès ces niveaux d’ARN mutés. Les ARNs antisens et les ribozymes, contrairement aux shRNA, ont permis un ciblage préférentiel des ARNs mutés de DMPK dans le noyau de myoblastes DM1. Ceci permet donc de maintenir un niveau basal de la protéine DMPK dans les myoblastes, un détail important advenant l’utilisation de ces molécules en thérapie génique chez l’humain. En utilisant les ribozymes, nous avons diminué la quantité et l’intensité des foci ce qui a permis de libérer les facteurs cellulaires se liant aux expansions de CUG. Ceci a eu comme effet de corriger un défaut d’épissage alternatif dans le récepteur à l’insuline. En exprimant de longs antisenses à l’ARNm de DMPK par un oncorétrovirus, nous avons constaté une restauration de la fusion cellulaire, de la capture de glucose ainsi qu’une diminution de CUGBP, un facteur d’épissage alternatif. Nous avons également démontré que la surexpression de hnRNP H, un facteur d’épissage liant les expansions de CUG, permettait aussi de diminuer les niveaux de CUGBP et ainsi corriger le défaut d’épissage alternatif du récepteur à l’insuline. Ces résultats démontrent donc pour la première fois le lien direct entre la rétention des ARNs mutés, la déplétion nucléaire d’un facteur d’épissage s’y liant et l’exacerbation de certaines caractéristiques du phénotype DM1. La somme de nos observations a permis deux choses importantes: en premier lieu, d’établir un nouveau modèle détaillé expliquant la pathogenèse de la DM1. En second lieu, nos résultats ont permi de valider la pertinence de détruire spécifiquement les transcrits mutés de DMPK afin de développer une thérapie génique efficace pour la DM1.Myotonic dystrophy type 1 (DM1) is a severe neuromuscular disease that ultimately causes loss of mobility and premature death. DM1 is the most common muscular dystrophy in adults with a world wide incidence of 1 affected individual in every 15 000. This disease is of special relevance in the Saguenay and Charlevoix regions in Quebec, where 1 in every 500 individuals is a carrier of the mutation. DM1 is caused by the expansion of an unstable CTG trinucleotide repeat located in 3’UTR of the DMPK (DM protein kinase) gene. However, it has been shown that most DM1 symptoms are related to the nuclear retention of mutant DMPK mRNA. These mutant transcripts bind to nuclear proteins and form foci in DM1 cell nuclei. This is though to be the leading cause of metabolical disruptions and defective alternative splicing of several mRNAs observed in DM1 cells. Our main project objective was to evaluate whether destruction of mutant DMPK mRNA could restore normal phenotype features in DM1 human skeletal myoblasts. The use of three RNA-based approaches: antisense RNAs, ribozymes and shRNAs, all displayed significant reductions in mutant DMPK mRNA. Antisense RNAs and ribozymes, as opposed to shRNAs, allowed specific targeting and destruction of mutant DMPK mRNAs in the nucleus of DM1 myoblasts. This feature thus allows a basal level of DMPK protein expression which is of particular relevance in the advent of developing a gene therapy for DM1. Ribozymes were effective in reducing the number and intensity of foci present in the nucleus of the myoblasts, thus allowing the release of certain CUG-binding proteins. This resulted in restoration of the defective splicing of the insulin receptor mRNA. Antisense RNAs to the DMPK mRNA expressed by an oncoretrovirus restored myoblast fusion, glucose uptake and lowered nuclear levels of CUGBP, an alternative splicing factor. Over expression of hnRNP-H, an alternative splicing factor that we showed could bind to CUG repeats, also reduces expression of CUGBP and restores defective splicing of the insulin receptor. These results reveal for the first time the intricate link between mutant DMPK mRNA nuclear retention, depletion of a CUG-binding protein that is also a splicing factor and exacerbation of related DM1 features. In conclusion, our work has allowed to better define the mechanisms involved in DM1 pathogenesis and has validated the relevance of developing a gene therapy that specifically targets mutant DMPK mRNAs

Human APOBEC3G Can Restrict Retroviral Infection in Avian Cells and Acts Independently of both UNG and SMUG1▿

APOBEC3 proteins are mammal-specific cytidine deaminases that can restrict retroviral infection. The exact mechanism of the restriction remains unresolved, but one model envisions that uracilated retroviral cDNA, generated by cytidine deamination, is the target of cellular glycosylases. While restriction is unaffected by UNG deficiency, it has been suggested that the SMUG1 glycosylase might provide a backup. We found that retroviral restriction can be achieved by introducing human APOBEC3G into chicken cells (consistent with the components necessary for APOBEC3-mediated restriction predating mammalian evolution) and used this assay to show that APOBEC3G-mediated restriction can occur in cells deficient in both UNG and SMUG1

The AKV Murine Leukemia Virus Is Restricted and Hypermutated by Mouse APOBEC3▿

APOBEC3 proteins are potent restriction factors against retroviral infection in primates. This restriction is accompanied by hypermutations in the retroviral genome that are attributable to the cytidine deaminase activity of the APOBEC3 proteins. Studies of nucleotide sequence diversity among endogenous gammaretroviruses suggest that the evolution of endogenous retroelements could have been shaped by the mutagenic cytidine deaminase activity of APOBEC3. In mice, however, APOBEC3 appears to restrict exogenous murine retroviruses in the absence of detectable levels of deamination. AKV is an endogenous retrovirus that is involved in causing a high incidence of thymic lymphoma in AKR mice. A comparative analysis of several mouse strains revealed a relatively low level of APOBEC3 expression in AKR mice. Here we show that endogenous mouse APOBEC3 restricts AKV infection and that this restriction likely reflects polymorphisms affecting APOBEC3 abundance rather than differences in the APOBEC3 isoforms expressed. We also observe that restriction of AKV by APOBEC3 is accompanied by G→A hypermutations in the viral genome. Our findings demonstrate that APOBEC3 acts as a restriction factor in rodents affecting the strain tropism of AKV, and they provide good support for the proposal that APOBEC3-mediated hypermutation contributed to the evolution of endogenous rodent retroviral genomes

SARS-CoV-2 Seroprevalence in Those Utilizing Public Transportation or Working in the Transportation Industry: A Rapid Review

Proximity and duration of social contact while working or using public transportation may increase users&rsquo; risk of SARS-CoV-2 exposure. This review aims to assess evidence of an association between use of public transportation or work in the transportation industry and prevalence of SARS-CoV-2 antibodies as well as to identify factors associated with seropositivity in transit users. A literature search of major databases was conducted from December 2019 to January 2022 using key worlds including &ldquo;seroprevalence&rdquo;, &ldquo;SARS-CoV-2&rdquo;, and &ldquo;public transit&rdquo;. A narrative review of included studies was completed for the following categories: those working in the transportation industry, healthcare workers relying on public transit, and population-based studies. The association between work in the transit industry and seroprevalence varied based on location, demographic characteristics, and test sensitivities. No association was found in healthcare workers. Several population-based studies indicated higher seroprevalence in those using public transit. Overall seroprevalence estimates varied based on geographic location, population demographics, study methodologies, and calendar date of assessment. However, seropositivity was consistently higher in racial minorities and low-income communities