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Harrison, A.

Publications and source records attributed to Harrison, A..

10 recordsLinked to original sources

Permissive central tolerance plus defective peripheral checkpoints licence pathogenic memory B cells in CASPR2-antibody encephalitis

Autoimmunity affects 10% of the population. Within this umbrella, autoantibody-mediated diseases targeting one autoantigen provide a unique opportunity to comprehensively understand the developmental pathway of disease-causing B cells and autoantibodies. While such autoreactivities are believed to be generated during germinal centre reactions, the roles of earlier immune checkpoints in autoantigen-specific B cell tolerance are poorly understood. We address this concept in patients with CASPR2-autoantibody encephalitis and healthy controls. In both groups, comparable and high ([~]0.5%) frequencies of unmutated CASPR2-reactive naive B cells were identified. By contrast, CASPR2-reactive memory B cells were exclusive to patients, and their B cell receptors demonstrated affinity-enhancing somatic mutations with heterogenous binding kinetics. These effector molecules possessed epitope-dependent pathogenic effects in vitro neuronal cultures and in vivo. The unmutated common ancestors of these memory B cells showed a distinctive balance between strong CASPR2 reactivity and very limited binding across the remaining human proteome. Our results are the first to propose mechanisms underlying autoantigen-specific tolerance in humans. We identify permissive central tolerance, defective peripheral tolerance and heterogenous autoantibody binding properties as sequential pathogenic steps which licence CASPR2-directed pathology. By leveraging the basic immunobiology, we rationally direct tolerance-restoring approaches in CASPR2-antibody diseases. This paradigm is applicable across autoimmune conditions.

immunology↗

Over supplementation of folic acid reduces survival 24 hours after hypoxia in male and female Drosophila melanogaster

Hypoxia is a major component of ischemic stroke. The prevalence of ischemic stroke is expected to increase as the global population ages and risk factors, like obesity, are on the rise. Nutrition is a modifiable risk factor for ischemic stroke. Increased dietary intake of folic acid (FA) has become an increasing problem in the U.S and other countries as more people are consuming at or above the recommended daily amount of FA. The impact of too much dietary FA on hypoxia is not well understood. This study aimed to investigate how increased dietary levels of FA impact hypoxia outcomes using Drosophila melanogaster as a model. Adult female and male w1118 Drosophila melanogaster flies were placed on control (CD) and 100 {micro}M folic acid (FAD) diets. At 5 to 6 days old fruit fly progeny were exposed to hypoxia for two hours prior to returning to normoxic conditions. We observed escape behavior in hypoxia larvae, confirming exposure to hypoxia. Using liquid chromatography-tandem mass spectrometry, elevated FA levels were observed in FAD compared to controls. We report increased acute hypoxia-induced mortality in FAD flies. Furthermore, FAD flies were not motivated to climb after hypoxia. Under normoxic conditions FAD flies had a higher velocity when descending during a climb. Interestingly, there was no impact of FA on apoptosis in brain tissue post-hypoxia. Together these data suggest that increase dietary intake of FA can have negative health outcomes after hypoxia. HighlightsO_LIHigh dietary folic acid and hypoxia increased mortality at the 24-hour time point. C_LIO_LIHypoxia and folic acid decreased motivation to climb and reduced movement in flies. C_LIO_LINo effect of hypoxia and folic acid on apoptosis levels in the fly brain tissue. C_LI

neuroscience↗

Apoptosis is increased in cortical neurons of female Marfan Syndrome mice

Marfan Syndrome (MFS) is an autosomal dominant genetic disorder that affects connective tissue throughout the body due to mutations in the FBN1 gene. Individuals with MFS display symptoms in different organs, particularly in the vasculature, but the mechanisms of this multi-system dysfunction are still under investigation. There is still a gap in our understanding of the impact of monogenic connective tissue aberrations on the brain. This study aims to determine the impact of MFS on neurodegeneration, in cortical brain tissue of male and female MFS mice. Brain tissue of 6-month-old female and male mice with the FBN1C1041G/+ mutation and wildtype litter mates was collected and stained for active caspase-3 (ac3), brain derived neurotrophic factor (BDNF), and neuronal nuclei (NeuN) or with TUNEL and DAPI. Data revealed increased levels of ac3 in neurons within the sensory and motor cortical areas of female MFS mice compared to sex- and age-matched controls. We confirm increased levels of apoptosis in MFS mice using TUNEL staining within the same brain areas. We also report increased levels of neuronal BDNF levels in cortical brain tissue of male and female MFS mice. These results indicate a heightened susceptibility for neurodegeneration in the mouse model of MFS. Significance StatementThe study revealed that female mice with a FBN1C1041G/+ mutation have more apoptotic neurons in sensory and motor cortical brain tissue compared to wildtype litter mates.

neuroscience↗

Antibodies generated in vitro and in vivo elucidate design of a thermostable ADDomer COVID-19 nasal nanoparticle vaccine

COVID-19 continues to damage populations, communities and economies worldwide. Vaccines have reduced COVID-19-related hospitalisations and deaths, primarily in developed countries. Persisting infection rates, and highly transmissible SARS-CoV-2 Variants of Concern (VOCs) causing repeat and breakthrough infections, underscore the ongoing need for new treatments to achieve a global solution. Based on ADDomer, a self-assembling protein nanoparticle scaffold, we created ADDoCoV, a thermostable COVID-19 candidate vaccine displaying multiple copies of a SARS-CoV-2 receptor binding motif (RBM)-derived epitope. In vitro generated neutralising nanobodies combined with molecular dynamics (MD) simulations and electron cryo-microscopy (cryo-EM) established authenticity and accessibility of the epitopes displayed. A Gigabody comprising multimerized nanobodies prevented SARS-CoV-2 virion attachment with picomolar EC50. Antibodies generated by immunising mice cross-reacted with VOCs including Delta and Omicron. Our study elucidates nasal administration of ADDomer-based nanoparticles for active and passive immunisation against SARS-CoV-2 and provides a blueprint for designing nanoparticle reagents to combat respiratory viral infections.

biochemistry↗

The role of insulators and transcription in 3D chromatin organisation of flies

The DNA in many organisms, including humans, is shown to be organised in topologically associating domains (TADs). In Drosophila, several architectural proteins are enriched at TAD borders, but it is still unclear whether these proteins play a functional role in the formation and maintenance of TADs. Here, we show that depletion of BEAF-32, Cp190, Chro and Dref leads to changes in TAD organisation and chromatin loops. Their depletion predominantly affects TAD borders located in heterochromatin, while TAD borders located in euchromatin are resilient to these mutants. Furthermore, transcriptomic data has revealed hundreds of genes displaying differential expression in these mutants and showed that the majority of differentially expressed genes are located within reorganised TADs. Our work identifies a novel and functional role for architectural proteins at TAD borders in Drosophila and a link between TAD reorganisation and subsequent changes in gene expression.

genomics↗

UBXN3B Restricts Viral Pathogenesis by Maintaining Hematopoietic Homeostasis

Hematopoiesis is finely regulated to enable timely production of the right numbers and types of mature immune cells to maintain tissue homeostasis. Dysregulated hematopoiesis may compromise antiviral immunity and/or exacerbate immunopathogenesis. Herein, we report an essential role of UBXN3B in maintenance of hematopoietic homeostasis and restriction of immunopathogenesis during respiratory viral infection. Ubxn3b deficient (Ubxn3b-/-) mice are highly vulnerable to SARS-CoV-2 and influenza A infection, characterized by more severe lung immunopathology, lower virus-specific IgG, significantly fewer B cells, but more myeloid cells than Ubxn3b+/+ littermates. This aberrant immune compartmentalization is recapitulated in uninfected Ubxn3b-/- mice. Mechanistically, UBXN3B controls precursor B-I (pre-BI) transition to pre-BII and subsequent proliferation in a cell-intrinsic manner, by maintaining BLNK protein stability and pre-BCR signaling. These results reveal an essential role of UBXN3B for the early stage of B cell development.

immunology↗

Lexical influences on categorical speech perception are driven by a temporoparietal circuit

Categorical judgments of otherwise identical phonemes are biased toward hearing words (i.e., "Ganong effect") suggesting lexical context influences perception of even basic speech primitives. Lexical biasing could manifest via late stage post-perceptual mechanisms related to decision or alternatively, top-down linguistic inference which acts on early perceptual coding. Here, we exploited the temporal sensitivity of EEG to resolve the spatiotemporal dynamics of these context-related influences on speech categorization. Listeners rapidly classified sounds from a /gi/ - /ki/ gradient presented in opposing word-nonword contexts (GIFT-kift vs. giss-KISS), designed to bias perception toward lexical items. Phonetic perception shifted toward the direction of words, establishing a robust Ganong effect behaviorally. ERPs revealed a neural analog of lexical biasing emerging within [~]200 ms. Source analyses uncovered a distributed neural network supporting the Ganong including middle temporal gyrus (MTG), inferior parietal lobe (IPL), and middle frontal cortex. Yet, among Ganong-sensitive regions, only left MTG and IPL predicted behavioral susceptibility to lexical influence. Our findings confirm lexical status rapidly constrains sub-lexical categorical representations for speech within several hundred milliseconds but likely does so outside the purview of canonical "auditory-linguistic" brain areas.

neuroscience↗

STING deficiency-associated aberrant CXCL10 expression contributes to pathogenesis of arthritogenic alphaviruses

Arthritogenic alphaviruses such as Chikungunya virus and Onyong nyong virus cause acute and chronic crippling arthralgia associated with inflammatory immune responses. However, the physiological functions of individual immune signaling pathways in the pathogenesis of alphaviral arthritis remain poorly understood. Here we report that a deficiency in the stimulator-of-interferon-genes (STING) led to enhanced viral loads, exacerbated inflammation and selectively elevated expression of CXCL10, a chemoattractant for monocytes/macrophages/T cells, in mouse feet. Cxcl10-/- mice had the same viremia as wild-type animals, but fewer immune infiltrates and lower viral loads in footpads at the peak of arthritic disease (6-8 days post infection). Macrophages constituted the largest immune cell population in footpads following infection, which were significantly reduced in Cxcl10-/- mice. The viral RNA loads in neutrophils and macrophages were reduced in Cxcl10-/- compared to wild-type mice. In summary, our results demonstrate that STING signaling represses, while CXCL10 signaling promotes, pathogenesis of alphaviral disease.

immunology↗

Spatio-temporally specific transcranial magnetic stimulation to test the locus of perceptual decision making in the human brain

Previous research modeling EEG, fMRI and behavioral data has identified three spatially distributed brain networks that activate in temporal sequence, and are thought to enable perceptual decision-making during face-versus-car categorization. These studies have linked late activation (>300ms post stimulus onset) in the lateral occipital cortex (LOC) to object discrimination processes. We applied paired-pulse transcranial magnetic stimulation (ppTMS) to LOC at different temporal latencies with the specific prediction, based on these studies, that ppTMS beginning at 400ms after stimulus onset would slow reaction time (RT) performance. Thirteen healthy adults performed a two-alternative forced choice task selecting whether a car or face was present on each trial amidst visual noise pre-titrated to approximate 79% accuracy. ppTMS, with pulses separated by 50ms, was applied at one of five stimulus onset asynchronies: -200, 200, 400, 450, or 500ms, and a sixth no-stimulation condition. As predicted, TMS at 400ms resulted in significant slowing of RTs, providing causal evidence in support of LOC contribution to perceptual decision processing. In addition, TMS delivered at -200ms resulted in faster RTs, indicating early stimulation may result in performance enhancement. These findings build upon correlational EEG and fMRI observations and demonstrate the use of TMS in predictive validation of psychophysiological models.

neuroscience↗

Mapping critical habitat of waterbirds in the Arctic for risk management in respect of IFC PS6

O_LIEconomic development and energy exploration are increasing in the Arctic. Important breeding habitats for many waterbird species, which have previously been relatively undisturbed, are now being subjected to these anthropogenic pressures. The conservation of the habitats and the species they support is a significant challenge for sustainable development. Even if governments and corporates operating in this fragile environment are committed to sustainable development, there is little information available to avoid, mitigate and manage environmental risk and impacts. Taking a risk management perspective, we followed the International Finance Corporations (IFC) Performance Standard 6 (PS6) criteria on Environmental and Social Sustainability and developed an approach to identify \"critical habitat\", as defined in IFC PS6, for waterbird species breeding in the Arctic. While the range of these waterbirds is roughly known, more accuracy is needed for proper risk assessment.\nC_LIO_LIWe have therefore gone a step further by modelling suitable habitat within these ranges. Depending on the relevance of the species for IFC PS6 and the level of certainty we separated the classes likely and potential critical habitat. We tested the approach for Russian breeding populations of five Anatidae species (White-fronted Goose Anser albifrons, Lesser White-fronted Goose Anser erythropus, Brent Goose Branta bernicla, Redbreasted Goose Branta ruficollis and Bewicks Swan Cygnus columbianus bewicki). Likely critical habitats were identified through a review of literature and available data for these waterbird species and multi-species congregations. To address the information gap for most of the Russian Arctic a species distribution modelling approach was used. The outputs of this approach were labelled as potential critical habitat, indicating the lower level of certainty than likely critical habitat.\nC_LIO_LIBased on existing information the amount of likely critical habitat is estimated to be at least x,xxx,xxx km2. For the five Anatidae species, X,XXX,XXX km2 potential critical habitat was identified; 95% of these areas were outside of the area boundaries of likely critical habitat for the species.\nC_LIO_LIInsufficient data in the east of the study area did affect the results, as some areas known to support breeding populations were not identified as suitable. Conversely, species distributions may be overpredicted in other areas; It should also be recognized that the analyzed species currently have depressed populations and may therefore only utilize a proportion of suitable habitat available.\nC_LIO_LIFor risk assessment purposes however, it is better to predict false positives, rather than false negatives. The study indicates that there are large areas in the Arctic that are potentially important for each of the Anatidae species modelled, but are not yet recognised as key important areas. The results confirm that there is still much to learn about waterbird distribution and abundance in the Russian Arctic.\nC_LIO_LISynthesis and applications The critical habitat maps produced do not just provide a new source of information for the economic development sector, but provide it in a way that is relevant to the sector and directly applicable. The maps are useful for initial risk assessments of potential developments, to identify likely impacts and to consider mitigation options, in accordance with IFC PS6. Risk assessors should exercise caution and detailed surveys for any development in areas predicted to be suitable for each species should be carried out.\nC_LI

ecology↗