Alphavirus Entry and Membrane Fusion

The study of enveloped animal viruses has greatly advanced our understanding of the general properties of membrane fusion and of the specific pathways that viruses use to infect the host cell. The membrane fusion proteins of the alphaviruses and flaviviruses have many similarities in structure and function. As reviewed here, alphaviruses use receptor-mediated endocytic uptake and low pH-triggered membrane fusion to deliver their RNA genomes into the cytoplasm. Recent advances in understanding the biochemistry and structure of the alphavirus membrane fusion protein provide a clearer picture of this fusion reaction, including the protein’s conformational changes during fusion and the identification of key domains. These insights into the alphavirus fusion mechanism suggest new areas for experimental investigation and potential inhibitor strategies for anti-viral therapy

Virus genomes reveal factors that spread and sustained the Ebola epidemic.

The 2013-2016 West African epidemic caused by the Ebola virus was of unprecedented magnitude, duration and impact. Here we reconstruct the dispersal, proliferation and decline of Ebola virus throughout the region by analysing 1,610 Ebola virus genomes, which represent over 5% of the known cases. We test the association of geography, climate and demography with viral movement among administrative regions, inferring a classic 'gravity' model, with intense dispersal between larger and closer populations. Despite attenuation of international dispersal after border closures, cross-border transmission had already sown the seeds for an international epidemic, rendering these measures ineffective at curbing the epidemic. We address why the epidemic did not spread into neighbouring countries, showing that these countries were susceptible to substantial outbreaks but at lower risk of introductions. Finally, we reveal that this large epidemic was a heterogeneous and spatially dissociated collection of transmission clusters of varying size, duration and connectivity. These insights will help to inform interventions in future epidemics

Immunothérapie du diabète auto-immun (de la prévention au traitement de la maladie établie)

Le but de notre travail a été de mettre en place des stratégies innovantes d'immuno-intervention permettant d'agir de manière efficace sur la progression du diabète auto-immun. Nous nous sommes focalisés sur deux stratégies : l'utilisation d'anticorps monoclonaux anti-CD3 et celle de produits bactériens. Les anticorps anti-CD3 possèdent la capacité remarquable d'induire une tolérance durable et spécifique vis-à-vis les antigènes du soi chez la souris NOD, spontanément diabétique. Nous avons établi et caractérisé des souris NOD transgéniques exprimant la molécule CD3s humaine (NOD-huCD3e). Cette souris développe un diabète auto-immun spontané identique à la souris NOD conventionnelle, est sensible au traitement par les anticorps anti-CD3 murins et humains et représente donc un modèle préclinique idéal. Dans un deuxième effort, nous avons étudié le rôle protecteur de certains composants bactériens, prioritairement des agonistes du récepteur Toll-like 4 (TLR4), sur la survenue du diabète.Our aim was the development of innovative strategies of immune-intervention allowing efficient interfering with progression of autoimmune diabetes, even at a late stage. We focussed on two strategies: usage of monoclonal anti-CD3 antibodies and of bacterial products. Anti-CD3 antibodies have the remarkable capacity to induce long-lasting and antigen-specific tolerance in NOD mice, which spontaneously develop diabetes. We generated and characterised transgenic NOD mice expressing the human CD3s chain (NOD-huCD3s). These mice spontaneously develop autoimmune diabetes, identical to conventional NOD mice, respond to treatment with murine- or human-specific anti-CD3 antibodies and thus present an ideal preclinical model. In a second effort, we studied the protective effect of certain bacterial products, primary of Toll-like receptor 4 (TLR4) agonists, on the development of diabetes. These molecules are interesting candidates for a transfer into the clinics.PARIS5-BU Méd.Cochin (751142101) / SudocSudocFranceF

Regulatory mechanisms of immune tolerance in type 1 diabetes and their failures

International audienc

Comparison of PET template-based and MRI-based image processing in the quantitative analysis of C11-raclopride PET

BACKGROUND Quantitative measures of 11C-raclopride receptor binding can be used as a correlate of postsynaptic D2 receptor density in the striatum, allowing 11C-raclopride positron emission tomography (PET) to be used for the differentiation of Parkinson's disease from atypical parkinsonian syndromes. Comparison with reference values is recommended to establish a reliable diagnosis. A PET template specific to raclopride may facilitate direct computation of parametric maps without the need for an additional MR scan, aiding automated image analysis. METHODS Sixteen healthy volunteers underwent a dynamic 11C-raclopride PET and a high-resolution T1-weighted MR scan of the brain. PET data from eight healthy subjects was processed to generate a raclopride-specific PET template normalized to standard space. Subsequently, the data processing based on the PET template was validated against the standard magnetic resonance imaging (MRI)-based method in 8 healthy subjects and 20 patients with suspected parkinsonian syndrome. Semi-quantitative image analysis was performed in Montreal Neurological Institute (MNI) and in original image space (OIS) using VOIs derived from a probabilistic brain atlas previously validated by Hammers et al. (Hum Brain Mapp, 15:165-174, 2002). RESULTS The striatal-to-cerebellar ratio (SCR) of 11C-raclopride uptake obtained using the PET template was in good agreement with the MRI-based image processing method, yielding a Lin's concordance coefficient of 0.87. Bland-Altman analysis showed that all measurements were within the ±1.96 standard deviation range. In all 20 patients, the PET template-based processing was successful and manual volume of interest optimization had no further impact on the diagnosis of PD in this patient group. A maximal difference of <5% was found between the measured SCR in MNI space and OIS. CONCLUSIONS The PET template-based method for automated quantification of postsynaptic D2 receptor density is simple to implement and facilitates rapid, robust and reliable image analysis. There was no significant difference between the SCR values obtained with either PET- or MRI-based image processing. The method presented alleviates the clinical workflow and facilitates automated image analysis