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Mouse models of Alzheimer's disease (AD) are valuable but do not fully recapitulate human AD pathology, such as spontaneous Tau fibril accumulation and neuronal loss, necessitating the development of new AD models. The transgenic (TG) TgF344-AD rat has been reported to develop age-dependent AD features including neuronal loss and neurofibrillary tangles, despite only expressing APP and PSEN1 mutations, suggesting an improved modelling of AD hallmarks. Alterations in neuronal networks as well as learning performance and cognition tasks have been reported in this model, but none have combined a longitudinal, multimodal approach across multiple centres, which mimics the approaches commonly taken in clinical studies. We therefore aimed to further characterise the progression of AD-like pathology and cognition in the TgF344-AD rat from young-adults (6 months (m)) to mid- (12 m) and advanced-stage (18 m, 25 m) of the disease. Methods: TgF344-AD rats and wild-type (WT) littermates were imaged at 6 m, 12 m and 18 m with [18F]DPA-714 (TSPO, neuroinflammation), [18F]Florbetaben (Aβ) and [18F]ASEM (α7-nicotinic acetylcholine receptor) and with magnetic resonance spectroscopy (MRS) and with (S)-[18F]THK5117 (Tau) at 15 and 25 m. Behaviour tests were also performed at 6 m, 12 m and 18 m. Immunohistochemistry (CD11b, GFAP, Aβ, NeuN, NeuroChrom) and Tau (S)-[18F]THK5117 autoradiography, immunohistochemistry and Western blot were also performed. Results: [18F]DPA-714 positron emission tomography (PET) showed an increase in neuroinflammation in TG vs wildtype animals from 12 m in the hippocampus (+11%), and at the advanced-stage AD in the hippocampus (+12%), the thalamus (+11%) and frontal cortex (+14%). This finding coincided with strong increases in brain microgliosis (CD11b) and astrogliosis (GFAP) at these time-points as assessed by immunohistochemistry. In vivo [18F]ASEM PET revealed an age-dependent increase uptake in the striatum and pallidum/nucleus basalis of Meynert in WT only, similar to that observed with this tracer in humans, resulting in TG being significantly lower than WT by 18 m. In vivo [18F]Florbetaben PET scanning detected Aβ accumulation at 18 m, and (S)-[18F]THK5117 PET revealed subsequent Tau accumulation at 25m in hippocampal and cortical regions. Aβ plaques were low but detectable by immunohistochemistry from 6 m, increasing further at 12 and 18 m with Tau-positive neurons adjacent to Aβ plaques at 18 m. NeuroChrom (a pan neuronal marker) immunohistochemistry revealed a loss of neuronal staining at the Aβ plaques locations, while NeuN labelling revealed an age-dependent decrease in hippocampal neuron number in both genotypes. Behavioural assessment using the novel object recognition task revealed that both WT & TgF344-AD animals discriminated the novel from familiar object at 3 m and 6 m of age. However, low levels of exploration observed in both genotypes at later time-points resulted in neither genotype successfully completing the task. Deficits in social interaction were only observed at 3 m in the TgF344-AD animals. By in vivo MRS, we showed a decrease in neuronal marker N-acetyl-aspartate in the hippocampus at 18 m (-18% vs age-matched WT, and -31% vs 6 m TG) and increased Taurine in the cortex of TG (+35% vs age-matched WT, and +55% vs 6 m TG). Conclusions: This multi-centre multi-modal study demonstrates, for the first time, alterations in brain metabolites, cholinergic receptors and neuroinflammation in vivo in this model, validated by robust ex vivo approaches. Our data confirm that, unlike mouse models, the TgF344-AD express Tau pathology that can be detected via PET, albeit later than by ex vivo techniques, and is a useful model to assess and longitudinally monitor early neurotransmission dysfunction and neuroinflammation in AD.

Background: The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might be curtailed by vaccination. We assessed the safety, reactogenicity, and immunogenicity of a viral vectored coronavirus vaccine that expresses the spike protein of SARS-CoV-2. Methods: We did a phase 1/2, single-blind, randomised controlled trial in five trial sites in the UK of a chimpanzee adenovirus-vectored vaccine (ChAdOx1 nCoV-19) expressing the SARS-CoV-2 spike protein compared with a meningococcal conjugate vaccine (MenACWY) as control. Healthy adults aged 18–55 years with no history of laboratory confirmed SARS-CoV-2 infection or of COVID-19-like symptoms were randomly assigned (1:1) to receive ChAdOx1 nCoV-19 at a dose of 5 × 10 10 viral particles or MenACWY as a single intramuscular injection. A protocol amendment in two of the five sites allowed prophylactic paracetamol to be administered before vaccination. Ten participants assigned to a non-randomised, unblinded ChAdOx1 nCoV-19 prime-boost group received a two-dose schedule, with the booster vaccine administered 28 days after the first dose. Humoral responses at baseline and following vaccination were assessed using a standardised total IgG ELISA against trimeric SARS-CoV-2 spike protein, a muliplexed immunoassay, three live SARS-CoV-2 neutralisation assays (a 50% plaque reduction neutralisation assay [PRNT 50]; a microneutralisation assay [MNA 50, MNA 80, and MNA 90]; and Marburg VN), and a pseudovirus neutralisation assay. Cellular responses were assessed using an ex-vivo interferon-γ enzyme-linked immunospot assay. The co-primary outcomes are to assess efficacy, as measured by cases of symptomatic virologically confirmed COVID-19, and safety, as measured by the occurrence of serious adverse events. Analyses were done by group allocation in participants who received the vaccine. Safety was assessed over 28 days after vaccination. Here, we report the preliminary findings on safety, reactogenicity, and cellular and humoral immune responses. The study is ongoing, and was registered at ISRCTN, 15281137, and ClinicalTrials.gov, NCT04324606. Findings: Between April 23 and May 21, 2020, 1077 participants were enrolled and assigned to receive either ChAdOx1 nCoV-19 (n=543) or MenACWY (n=534), ten of whom were enrolled in the non-randomised ChAdOx1 nCoV-19 prime-boost group. Local and systemic reactions were more common in the ChAdOx1 nCoV-19 group and many were reduced by use of prophylactic paracetamol, including pain, feeling feverish, chills, muscle ache, headache, and malaise (all p80 and in 35 (100%) participants when measured in PRNT 50. After a booster dose, all participants had neutralising activity (nine of nine in MNA 80 at day 42 and ten of ten in Marburg VN on day 56). Neutralising antibody responses correlated strongly with antibody levels measured by ELISA (R 2=0·67 by Marburg VN; p

BackgroundProgression of Alzheimer’s disease is thought initially to depend on rising amyloidβ and its synaptic interactions. Transgenic mice (TASTPM; APPSwe/PSEN1M146V) show altered synaptic transmission, compatible with increased physiological function of amyloidβ, before plaques are detected. Recently, the importance of microglia has become apparent in the human disease. Similarly, TASTPM show a close association of plaque load with upregulated microglial genes.MethodsCA1 Synaptic transmission and plasticity were investigated using in vitro electrophysiology. Migroglial relationship to plaques was examined with immunohistochemistry. Behaviour was assessed with a forced-alternation T-maze, open field, light/dark box and elevated plus maze.FindingsThe most striking finding is the increase in microglial numbers in TASTPM, which, like synaptic changes, begins before plaques are detected. Further increases and a reactive phenotype occur later, concurrent with development of larger plaques. Long-term potentiation is initially enhanced at pre-plaque stages but decrements with the initial appearance of plaques. Finally, despite altered plasticity, TASTPM have little cognitive deficit, even with a heavy plaque load, although they show altered non-cognitive behaviours.InterpretationThe pre-plaque synaptic changes and microglial proliferation are presumably related to low, non-toxic amyloidβ levels in the general neuropil and not directly associated with plaques. However, as plaques grow, microglia proliferate further, clustering around plaques and becoming phagocytic. Like in humans, even when plaque load is heavy, without development of neurofibrillary tangles and neurodegeneration, these alterations do not result in cognitive deficits. Behaviours are seen that could be consistent with pre-diagnosis changes in the human condition.Research in contextEvidence before this studyThere is a large body of research examining many aspects of phenotypes associated with mouse models of Alzheimer’s disease – a PubMed search for the terms Alzheimer* AND mouse returns in excess of 21000 articles. However, there are few systematic articles pulling together pathological, functional (electrophysiological), and behavioural analyses across the life-span of such models. There is also a number of conflicting outcomes, for example reports of impaired versus enhanced synaptic plasticity; cognitive impairments or not.Recently, the importance of microglia in Alzheimer’s disease has come to the fore in human Genome Wide Association Studies (GWAS), with variants of a number of microglial genes identified as risk-factors for developing the disease. Interestingly, we have recently reported that Trem2 and other genes identified as risk-factors in humans are strongly up regulated in close association to plaque development in the mouse model used in this study. Moreover, this previous study predicted two of the most recently identified genes that were identified in GWAS since the publication of our paper.We have previously used this model to identify the earliest synaptic changes and shown changes in release of glutamate, the primary excitatory neurotransmitter in the brain, to occur even before plaques are detectable.Added value of this studyBy studying this transgenic mouse model of Alzheimer’s disease, throughout the development of plaques, from prior to detection through to heavy plaque loads, we have been able to identify a clear time course of key phenotypic changes associated with early disease. In particular, this study identifies the very early changes in microglia and can separate the time course of the microglial phenotype. In addition, we detail the changes in synaptic plasticity over time and importantly identify that, like in humans in the absence of Tau tangles or neurodegeneration, considerable synaptic changes can occur and a heavy plaque load without resulting in substantial cognitive loss.Implications of all the available evidenceOur data indicate that rising amyloid beta prior to detectable plaque deposition results in changes in synaptic function that likely reflects an enhanced physiological effect of amyloid beta. At this stage, microglia proliferate but do not activate. Once plaques begin to appear, microglia migrate to surround the plaque and become phagocytic, likely targeting dystrophic synapses and neurites caused by the cloud of highly-toxic amyloid beta around the plaque. Similarly to humans, who have plaques but no tangles and have yet to develop substantial neurodegeneration, cognitive deficits are not seen, even with a heavy plaque load; behavioural changes are limited to anxiety-like effects.This investigation of the parallel time-course of events highlights the probability that, if progression of disease can be reversed or slowed early enough, before Tau tangles and substantial neurodegeneration occur, the symptoms of cognitive decline could be very largely avoided. Moreover, it suggests that the substantial increases in microglia number and upregulation of their specific gene expression in association with plaques, is not associated with cognitive loss and may indeed be protective.

Genome-wide association studies have reported that, amongst other microglial genes, variants inTREM2can profoundly increase the incidence of developing Alzheimer’s disease (AD). We have investigated the role of TREM2 in primary microglial cultures from wild type mice by using siRNA to decreaseTrem2expression, and in parallel from knock-in mice heterozygous or homozygous for theTrem2R47H AD risk variant. The prevailing phenotype ofTrem2R47H knock-in mice was decreased expression levels ofTrem2in microglia, which resulted in decreased density of microglia in the hippocampus. Overall, primary microglia with reducedTrem2expression, either by siRNA or from the R47H knock-in mice, displayed a similar phenotype. Comparison of the effects of decreasedTrem2expression under conditions of LPS pro-inflammatory or IL-4 anti-inflammatory stimulation revealed the importance ofTrem2in driving a number of the genes up-regulated in the anti-inflammatory phenotype. RNA-seq analysis showed that IL-4 induced the expression of a programme of genes includingArg1andAp1b1in microglia, which showed an attenuated response to IL-4 whenTrem2expression was decreased. Genes showing a similar expression profile toArg1were enriched for STAT6 transcription factor recognition elements in their promoter, andTrem2knockdown decreased levels of the transcription factor STAT6. LPS-induced pro-inflammatory stimulation suppressedTrem2expression, thus preventing TREM2’s anti-inflammatory drive. Given that anti-inflammatory signaling is associated with tissue repair, understanding the signaling mechanisms downstream ofTrem2in coordinating the pro- and anti-inflammatory balance of microglia, particularly mediating effects of the IL-4-regulated anti-inflammatory pathway, has important implications for fighting neurodegenerative disease.Graphical abstract

Hippocampal pathology is likely to contribute to cognitive disability in Down syndrome, yet the neural network basis of this pathology and its contributions to different facets of cognitive impairment remain unclear. Here we report dysfunctional connectivity between dentate gyrus and CA3 networks in the transchromosomic Tc1 mouse model of Down syndrome, demonstrating that ultrastructural abnormalities and impaired short-term plasticity at dentate gyrus-CA3 excitatory synapses culminate in impaired coding of new spatial information in CA3 and CA1 and disrupted behavior in vivo. These results highlight the vulnerability of dentate gyrus-CA3 networks to aberrant human chromosome 21 gene expression and delineate hippocampal circuit abnormalities likely to contribute to distinct cognitive phenotypes in Down syndrome.

In many brain regions, Ca2+ influx through presynaptic P2X receptors influences GABA release from interneurones. In patch-clamp recordings of Purkinje cells (PCs) in rat cerebellar slices, broad spectrum P2 receptor antagonists, PPADS (30 mu M) or suramin (12 mu M), result in a decreased amplitude and increased failure rate of minimal evoked GABAergic synaptic currents from basket cells. The effect is mimicked by desensitizing P2X1/3-containing receptors with alpha,beta-methylene ATP. This suggests presynaptic facilitation of GABA release via P2XR-mediated Ca2+ influx activated by endogenously released ATP. In contrast, activation of P2Y4 receptors (using UTP, 30 mu M, but not P2Y1 or P2Y6 receptor ligands) results in inhibition of GABA release. Immunological studies reveal the presence of most known P2Rs in >= 20% of GABAergic terminals in the cerebellum. P2X3 receptors and P2Y4 receptors occur in approximately 60% and 50% of GABAergic synaptosomes respectively and are localized presynaptically. Previous studies report that PC output is also influenced by postsynaptic purinergic receptors located on both PCs and interneurones.The high Ca2+ permeability of the P2X receptor and the ability of ATP to influence intracellular Ca2+ levels via P2Y receptor-mediated intracellular pathways make ATP the ideal transmitter for the multisite bidirectional modulation of the cerebellar cortical neuronal network. (c) 2008 Published by Elsevier Ltd.

Background Neural stem cells (NSCs) are powerful research tools for the design and discovery of new approaches to neurodegenerative disease. Overexpression of the myc family transcription factors in human primary cells from developing cortex and mesencephalon has produced two stable multipotential NSC lines (ReNcell VM and CX) that can be continuously expanded in monolayer culture. Results In the undifferentiated state, both ReNcell VM and CX are nestin positive and have resting membrane potentials of around -60 mV but do not display any voltage-activated conductances. As initially hypothesized, using standard methods (stdD) for differentiation, both cell lines can form neurons, astrocytes and oligodendrocytes according to immunohistological characteristics. However it became clear that this was not true for electrophysiological features which designate neurons, such as the firing of action potentials. We have thus developed a new differentiation protocol, designated 'pre-aggregation differentiation' (preD) which appears to favor development of electrophysiologically functional neurons and to lead to an increase in dopaminergic neurons in the ReNcell VM line. In contrast, the protocol used had little effect on the differentiation of ReNcell CX in which dopaminergic differentiation was not observed. Moreover, after a week of differentiation with the preD protocol, 100% of ReNcell VM featured TTX-sensitive Na+-channels and fired action potentials, compared to 25% after stdD. Currents via other voltage-gated channels did not appear to depend on the differentiation protocol. ReNcell CX did not display the same electrophysiological properties as the VM line, generating voltage-dependant K+ currents but no Na+ currents or action potentials under either stdD or preD differentiation. Conclusion These data demonstrate that overexpression of myc in NSCs can be used to generate electrophysiologically active neurons in culture. Development of a functional neuronal phenotype may be dependent on parameters of isolation and differentiation of the cell lines, indicating that not all human NSCs are functionally equivalent.

We provide microarray data comparing genome-wide differential expression and pathology throughout life in four lines of "amyloid" transgenic mice (mutant human APP, PSEN1, or APP/PSEN1) and "TAU" transgenic mice (mutant human MAPT gene). Microarray data were validated by qPCR and by comparison to human studies, including genome-wide association study (GWAS) hits. Immune gene expression correlated tightly with plaques whereas synaptic genes correlated negatively with neurofibrillary tangles. Network analysis of immune gene modules revealed six hub genes in hippocampus of amyloid mice, four in common with cortex. The hippocampal network in TAU mice was similar except that Trem2 had hub status only in amyloid mice. The cortical network of TAU mice was entirely different with more hub genes and few in common with the other networks, suggesting reasons for specificity of cortical dysfunction in FTDP17. This Resource opens up many areas for investigation. All data are available and searchable at http://www.mouseac.org. Fil: Matarin, Mar. Queen Square. Institute of Neurology. Department of Clinical and Experimental Epilepsy; Reino Unido. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Salih, Dervis A.. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Yasvoina, Marina. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Cummings, Damian M.. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Guelfi, Sebastian. Institute of Neurology. Reta Lila Research Laboratories and Department of Molecular Neuroscience; Reino Unido Fil: Liu, Wenfei. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: NahabooSolim, Muzammil A.. Physiology and Pharmacology. Department of Neuroscience; Reino Unido. Queen Square. UCL Institute of Neurology. Department of Neuroinflammation; Reino Unido Fil: Moens, Thomas G.. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Paublete, Rocio Moreno. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Ali, Shabinah S.. Physiology and Pharmacology. Department of Neuroscience; Reino Unido Fil: Perona, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Queen Square. Institute of Neurology. Department of Clinical and Experimental Epilepsy; Reino Unido Fil: Desai, Roshni. Queen Square. UCL Institute of Neurology. Department of Neuroinflammation; Reino Unido Fil: Smith, Kenneth J.. Queen Square. UCL Institute of Neurology. Department of Neuroinflammation; Reino Unido Fil: Latcham, Judy. GlaxoSmithKline R&D. Department of Laboratory Animal Science; Reino Unido Fil: Fulleylove, Michael. GlaxoSmithKline R&D. Department of Laboratory Animal Science; Reino Unido Fil: Richardson, Jill C.. GlaxoSmithKline R&D. Neurosciences Therapeutic Area; Reino Unido Fil: Hardy, John. Queen Square. Institute of Neurology. Department of Clinical and Experimental Epilepsy; Reino Unido Fil: Edwards, Frances A.. Queen Square. Institute of Neurology. Department of Clinical and Experimental Epilepsy; Reino Unido