Biology subjects

Owen, A.

Publications and source records attributed to Owen, A..

31 records · Page 2Linked to original sources

bioRxiv2021

Single-dose immunisation with a multimerised SARS-CoV-2 receptor binding domain (RBD) induces an enhanced and protective response in mice

The COVID-19 pandemic, caused by the SARS-CoV-2 coronavirus, has triggered a worldwide health emergency. So far, several different types of vaccines have shown strong efficacy. However, both the emergence of new SARS-CoV-2 variants and the need to vaccinate a large fraction of the worlds population necessitate the development of alternative vaccines, especially those that are simple and easy to store, transport and administer. Here, we showed that ferritin-like Dps protein from hyperthermophilic Sulfolobus islandicus can be covalently coupled with different SARS-CoV-2 antigens via the SpyCatcher system, to form extremely stable and defined multivalent dodecameric vaccine nanoparticles that remain intact even after lyophilisation. Immunisation experiments in mice demonstrated that the SARS-CoV-2 receptor binding domain (RBD) coupled to Dps (RBD-S-Dps) shows particular promise as it elicited a higher antibody titre and an enhanced neutralising antibody response compared to the monomeric RBD. Furthermore, we showed that a single immunisation with the multivalent RBD-S-Dps completely protected hACE2-expressing mice from serious illness and led to efficient viral clearance from the lungs upon SARS-CoV-2 infection. Our data highlight that multimerised SARS-CoV-2 subunit vaccines are a highly efficacious modality, particularly when combined with an ultra-stable scaffold.

immunology↗

bioRxiv2021

Viral neuroinvasion and neurotropism without neuronal damage in the hACE2 mouse model of COVID-19

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) not only affects the respiratory tract but also causes neurological symptoms such as loss of smell and taste, headache, fatigue or severe cerebrovascular complications. Using transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2) we investigated the spatiotemporal distribution and pathomorphological features in the CNS following intranasal infection with SARS-CoV-2 variants, also after prior influenza A virus infection. Apart from Omicron, we found all variants to frequently spread to and within the CNS. Infection was restricted to neurons and appeared to spread from the olfactory bulb mainly in basally orientated regions in the brain and into the spinal cord, independent of ACE2 expression and without evidence of neuronal cell death, axonal damage or demyelination. However, microglial activation, microgliosis and a mild macrophage and T cell dominated inflammatory response was consistently observed, accompanied by apoptotic death of endothelial, microglial and immune cells, without their apparent infection. Microgliosis and immune cell apoptosis indicate a potential role of microglia for pathogenesis and viral effect in COVID-19 and possible impairment of neurological functions, especially in long COVID. These data may also be informative for the selection of therapeutic candidates, and broadly support investigation of agents with adequate penetration into relevant regions of the CNS.

pathology↗

bioRxiv2021

Naturally-acquired immunity in Syrian Golden Hamsters provides protection from re-exposure to emerging heterosubtypic SARS-CoV-2 variants B.1.1.7 and B.1.351

The ability of acquired immune responses against SARS-CoV-2 to protect after subsequent exposure to emerging variants of concern (VOC) such as B1.1.7 and B1.351 is currently of high significance. Here, we use a hamster model of COVID-19 to show that prior infection with a strain representative of the original circulating lineage B of SARS-CoV-2 induces protection from clinical signs upon subsequent challenge with either B1.1.7 or B1.351 viruses, which recently emerged in the UK and South Africa, respectively. The results indicate that these emergent VOC may be unlikely to cause disease in individuals that are already immune due to prior infection, and this has positive implications for overall levels of infection and COVID-19 disease.

microbiology↗

bioRxiv2021

Development of a highly sensitive bioanalytical assay for the quantification of favipiravir.

Favipiravir (FAV; T-705) has been approved for use as an anti-influenza therapeutic and has reports against a wide range of viruses (e.g., Ebola virus, rabies and norovirus). Most recently FAV has been reported to demonstrate activity against SARS-CoV-2. Repurposing opportunities have been intensively studied with only limited success to date. If successful, repurposing will allow interventions to become more rapidly available than development of new chemical entities. Pre-clinical and clinical investigations of FAV require robust, reproducible and sensitive bioanalytical assay. Here, a liquid chromatography tandem mass spectrometry assay is presented which was linear from 0.78-200 ng/mL Accuracy and precision ranged between 89% and 110%, 101% and 106%, respectively. The presented assay here has applications in both pre-clinical and clinical research and may be used to facilitate further investigations into the application of FAV against SARS-CoV-2.

pharmacology and toxicology↗

bioRxiv2021

Optimisation and validation of a sensitive bioanalytical method for niclosamide.

The SARS-CoV-2 pandemic has spread at an unprecedented rate, and repurposing opportunities have been intensively studied with only limited success to date. If successful, repurposing will allow interventions to become more rapidly available than development of new chemical entities. Niclosamide has been proposed as a candidate for repurposing for SARS-CoV-2 based upon the observation that it is amongst the most potent antiviral molecules evaluated in vitro. To investigate the pharmacokinetics of niclosamide, reliable, reproducible and sensitive bioanalytical assays are required. Here, a liquid chromatography tandem mass spectrometry assay is presented which was linear from 31.25-2000 ng/mL (high dynamic range) and 0.78-100 ng/mL (low dynamic range). Accuracy and precision ranged between 97.2% and 112.5%, 100.4% and 110.0%, respectively. The presented assay should have utility in preclinical evaluation of the exposure-response relationship and may be adapted for later evaluation of niclosamide in clinical trials.

pharmacology and toxicology↗

bioRxiv2020

Remdesivir-Ivermectin combination displays synergistic interaction with improved in vitro antiviral activity against SARS-CoV-2

A key element for the prevention and management of COVID-19 is the development of effective therapeutics. Drug combination strategies of repurposed drugs offer several advantages over monotherapies, including the potential to achieve greater efficacy, the potential to increase the therapeutic index of drugs and the potential to reduce the emergence of drug resistance. Here, we report on the in vitro synergistic interaction between two FDA approved drugs, remdesivir and ivermectin resulting in enhanced antiviral activity against SARS-CoV-2. These findings warrant further investigations into the clinical potential of this combination, together with studies to define the underlying mechanism.

microbiology↗

bioRxiv2020

A Quantitative Measurement to Describe the Relative Proximity of Fluorescent Biomarkers

Determining the relationship between biomarkers via fluorescence microscopy is a key step in the characterisation of cellular phenotypes. We define a simple distance-based measurement termed a perimeter distance mean (PDmean) which quantifies the relative proximity of objects in one fluorescent channel to objects in a second fluorescent channel in 2D or 3D microscopy datasets. PDmean measurements were able to accurately identify known changes in colocalisation in computer-generated and real-world microscopy datasets. We argue that this approach provides substantial advantages over currently used distance-based colocalisation analysis methods. We also introduce PyBioProx, an extensible open-source Python module and graphical user interface that produces PDmean measurements.

bioinformatics↗

bioRxiv2020

Sequential infection with influenza A virus followed by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leads to more severe disease and encephalitis in a mouse model of COVID-19.

COVID-19 is a spectrum of clinical symptoms in humans caused by infection with SARS-CoV-2, a recently emerged coronavirus that rapidly caused a pandemic. Coalescence of this virus with seasonal respiratory viruses, particularly influenza virus is a global health concern. To investigate this, transgenic mice expressing the human ACE2 receptor driven by the epithelial cell cytokeratin-18 gene promoter (K18-hACE2) were first infected with IAV followed by SARS-CoV-2. The host response and effect on virus biology was compared to K18-hACE2 mice infected with IAV or SARS-CoV-2 only. Infection of mice with each individual virus resulted in a disease phenotype compared to control mice. Although SARS-CoV-2 RNA synthesis appeared significantly reduced in the sequentially infected mice, they exhibited more rapid weight loss, more severe lung damage and a prolongation of the innate response compared to singly infected or control mice. The sequential infection also exacerbated the extrapulmonary encephalitic manifestations associated with SARS-CoV-2 infection. Conversely, prior infection with a commercially available, multivalent live-attenuated influenza vaccine (Fluenz tetra) elicited the same reduction in SARS-CoV-2 RNA synthesis albeit without the associated increase in disease severity. This suggests that the innate immune response stimulated by infection with IAV is responsible for the observed inhibition of SARS-CoV-2, however, infection with attenuated, apathogenic influenza vaccine does not result in an aberrant immune response and enhanced disease severity. Taken together, the data suggest that the concept of twinfection is deleterious and mitigation steps should be instituted as part of a comprehensive public health response to the COVID-19 pandemic.

microbiology↗

bioRxiv2019

N-acetyltransferase 2 genotypes amongst ulu Speaking South Africans and isoniazid / N-acetyl-isoniazid pharmacokinetics during ant-tuberculosis treatment

BackgroundDistribution of N-acetyltransferase2 (NAT2) polymorphisms varies considerably among different ethnic groups. Information on NAT2 single-nucleotide polymorphisms in South African population is limited. We investigated NAT2 polymorphisms and their effect on isoniazid pharmacokinetics in Zulu black HIV-infected South Africans in Durban, South Africa. Methods: HIV-infected participants with culture-confirmed pulmonary tuberculosis (TB) were enrolled from two unrelated studies. Culture-confirmed participants were genotyped for NAT2 polymorphisms 282C>T, 341T>C, 481C>T, 857G>A, 590G>A and 803A>G using Life Technologies pre-validated Taqman assays (Life Technologies, Paisley, UK). Participants underwent sampling for determination of plasma isoniazid and N-acetylisoniazid concentrations. ResultsAmongst the 120 patients, 63/120 (52.5%) were slow metabolisers (NAT2*5/*5), 43/120 (35.8%) had intermediate (NAT2*5/12), and 12/120 (11.7%) had rapid genotype (NAT2*4/*11, NAT2*11/12 and NAT2*12/12). NAT2 alleles in this study were *4, *5C, *5D, *5E, *5J, *5K, *5KA, *5T, *11A, *12A/12C and *12M. NAT2*5 was the most frequent allele (70.4%) followed by NAT2*12 (27.9%). 34/40 had both PK results and NAT2 genotyping results. The median area under the concentration-time-curve to infinity (AUC0-{infty}) interquartile range (IQR) was 7.81 (5.87 - 16.83) g/ml/hr and maximum concentration (Cmax) 3.14 g/ml (2.42 - 4.36) g/mL. Individual polymorphisms were not equally distributed, with some represented in small numbers. Genotype did not correlate with phenotype, rapid genotype showing higher AUC0-{infty} than slow but not significant, p=0.43. ConclusionThere was high prevalence of slow followed by intermediate then rapid acetylator genotypes. The poor concordance between genotype and phenotype suggests that other factors or genetic loci influence INH metabolism, and warrants further investigation in this population.

genetics↗

bioRxiv2019

Consciousness & Brain Functional Complexity in Propofol Anaesthesia

The brain is possibly the most complex system known to mankind, and its complexity has been called upon to explain the emergence of consciousness. However, complexity can take many forms: here, we investigate measures of algorithmic and process complexity in both the temporal and topological dimension, testing them on functional MRI data obtained from individuals undergoing various levels of sedation with the anaesthetic agent propofol, in two separate datasets. We demonstrate that the various measures are differently able to discriminate between levels of sedation, with temporal measures showing higher sensitivity. Further, we show that all measures are strongly related to a single underlying construct explaining most of the variance, as assessed by Principal Component Analysis, which we interpret as a measure of overall complexity of our data. This overall complexity was also able to discriminate between levels of sedation, supporting the hypothesis that consciousness is related to complexity - independent of how the latter is measured.

neuroscience↗

bioRxiv2019

Context-specific effects of facial dominance and trustworthiness on hypothetical leadership decisions

Social judgments of faces predict important social outcomes, including leadership decisions. Previous work suggests that facial cues associated with perceptions of dominance and trustworthiness have context-specific effects on leadership decisions. Facial cues linked to perceived dominance have been found to be preferred in leaders for hypothetical wartime contexts and facial cues linked to perceived trustworthiness have been found to be preferred in leaders for hypothetical peacetime contexts. Here we sought to replicate these effects using images of womens faces. Consistent with previous work, a linear mixed effects model demonstrated that more trustworthy-looking faces were preferred in leaders during times of peace and more dominant-looking faces were preferred in leaders during times of war. These results provide converging evidence for context-specific effects of facial cues on hypothetical leadership judgments.

animal behavior and cognition↗

bioRxiv2019

The emergence of integrated information, complexity, andconsciousness at criticality

Using the critical Ising model of the brain, integrated information as a measure of consciousness is measured in toy models of generic neural networks. Monte Carlo simulations are run on 159 random weighted networks analogous to small 5-node neural network motifs. The integrated information generated by this sample of small Ising models is measured across the model parameter space. It is observed that integrated information, as a type of order parameter not unlike a concept like magnetism, undergoes a phase transition at the critical point in the model. This critical point is demarcated by the peaks of the generalized susceptibility of integrated information, a point where the consciousness of the system is maximally susceptible to perturbations and on the boundary between an ordered and disordered form. This study adds further evidence to support that the emergence of consciousness coincides with the more universal patterns of self-organized criticality, evolution, the emergence of complexity, and the integration of complex systems.\n\nAuthor summaryUnderstanding consciousness through a scientific and mathematical language is slowly coming into reach and so testing and grounding these emerging ideas onto empirical observations and known systems is a first step to properly framing this ancient problem. This paper in particular explores the Integrated Information Theory of Consciousness framed within the physics of the Ising model to understand how and when consciousness, or integrated information, can arise in simple dynamical systems. The emergence of consciousness is treated like the emergence of other classical macroscopic observables in physics such as magnetism and understood as a dynamical phase of matter. Our findings show that the sensitivity of consciousness in a complex system is maximized when the system is undergoing a phase transition, also known as a critical point. This result, combined with a body of evidence highlighting the privelaged state of critical systems suggests that, like many other complex phenomenon, consciousness may simply follow from/emerge out of the tendency of a system to self-organize to criticality.

neuroscience↗

bioRxiv2018

A Genetic Program Mediates Cold-warming Response and Promotes Stress-induced Phenoptosis in C. elegans

How multicellular organisms respond to and are impacted by severe hypothermic stress is largely unknown. From C. elegans screens for mutants abnormally responding to cold-warming stimuli, we identify a molecular genetic pathway comprising ISY-1, a conserved uncharacterized protein, and ZIP-10, a bZIP-type transcription factor. ISY-1 gatekeeps the ZIP-10 transcriptional program by regulating the microRNA mir-60. Downstream of ISY-1 and mir-60, zip-10 levels rapidly and specifically increase upon transient cold-warming response. Prolonged zip-10 up-regulation induces several protease-encoding genes and promotes stress-induced organismic death, or phenoptosis, of C. elegans. zip-10 deficiency confers enhanced resistance to prolonged cold-warming stress, more prominently in adults than larvae. We conclude that the ZIP-10 genetic program mediates cold-warming response and may have evolved to promote wild population kin selection under resource-limiting and thermal stress conditions.

genetics↗