5 research outputs found
Exploiting the Time-Reversal Operator for Adaptive Optics, Selective Focusing and Scattering Pattern Analysis
We report on the experimental measurement of the backscattering matrix of a
weakly scattering medium in optics, composed of a few dispersed gold nanobeads.
The DORT method (Decomposition of the Time Reversal Operator) is applied to
this matrix and we demonstrate selective and efficient focusing on individual
scatterers, even through an aberrating layer. Moreover, we show that this
approach provides the decomposition of the scattering pattern of a single
nanoparticle. These results open important perspectives for optical imaging,
characterization and selective excitation of nanoparticles.Comment: 10 page
Fourier transform acousto-optic imaging with off-axis holographic detection
International audienceAcousto-optic (AO) imaging is an in-depth optical imaging technique of highly scattering media. One challenging end-application for this technique is to perform imaging of living biological tissues. Indeed, because it relies on coherent illumination, AO imaging is sensitive to speckle decorrelation occurring on the millisecond time scale. Camera-based detections are well suited for in vivo imaging provided their integration time is lower than those decorrelation time scales. We present Fourier transform acousto-optic imaging combined with off-axis holography, which relies on plane waves and long-duration pulses. We demonstrate, for the first time to the best of our knowledge, a two-dimensional imaging system fully compatible with in vivo imaging prerequisites. The method is validated experimentally by performing in-depth imaging inside a multiple scattering sample
Characterization of a highly neutralizing single monoclonal antibody to botulinum neurotoxin type A
International audienceCompared to conventional antisera strategies, monoclonal antibodies (mAbs) represent an alternative and safer way to treat botulism, a fatal flaccid paralysis due to botulinum neurotoxins (BoNTs). In addition, mAbs offer the advantage to be produced in a reproducible manner. We previously identified a unique and potent mouse mAb (TA12) targeting BoNT/A1 with high affinity and neutralizing activity. In this study, we characterized the molecular basis of TA12 neutralization by combining Hydrogen/Deuterium eXchange Mass Spectrometry (HDX-MS) with site-directed mutagenesis and functional studies. We found that TA12 recognizes a conformational epitope located at the interface between the HCN and HCC subdomains of the BoNT/A1 receptor-binding domain (HC ). The TA12-binding interface shares common structural features with the ciA-C2 VHH epitope and lies on the face opposite recognized by ciA-C2- and the CR1/CR2-neutralizing mAbs. The single substitution of N1006 was sufficient to affect TA12 binding to HC confirming the position of the epitope. We further uncovered that the TA12 epitope overlaps with the BoNT/A1-binding site for both the neuronal cell surface receptor synaptic vesicle glycoprotein 2 isoform C (SV2C) and the GT1b ganglioside. Hence, TA12 potently blocks the entry of BoNT/A1 into neurons by interfering simultaneously with the binding of SV2C and to a lower extent GT1b. Our study reveals the unique neutralization mechanism of TA12 and emphasizes on the potential of using single mAbs for the treatment of botulism type A
Un cas de botulisme bovin massif : investigation épidémiologique
National audienceDepuis quelques annĂ©es, de plus en plus de foyers de botulisme bovin de type D sont signalĂ©s en Europe avec une forte suspicion dâimplication de fumiers de volaille, mais sans que les circonstances exactes dâexposition des bovins aux toxines de Clostridium botulinum nâaient pu ĂȘtre identifiĂ©es. En juin 2015, le service de MĂ©decine des Animaux dâElevage dâOniris a Ă©tĂ© sollicitĂ© pour identifier lâorigine dâun foyer sĂ©vĂšre de botulisme bovin survenu dans une exploitation ayant des ateliers de bovins et de volailles. En lâespace de 2 mois, 80 des 110 vaches laitiĂšres Ă©taient mortes aprĂšs avoir manifestĂ© des signes cliniques de botulisme, sans que lâorigine du foyer nâait pu ĂȘtre dĂ©terminĂ©e. Les autopsies avaient montrĂ© une absence de lĂ©sions significatives et les prĂ©lĂšvements de contenus intestinaux avaient identifiĂ© la prĂ©sence de C. botulinum de type D/C. Les investigations Ă©pidĂ©miologiques et les analyses rĂ©alisĂ©es suggĂšrent fortement que ce foyer soit dĂ» Ă lâingestion dâun ensilage dâherbe insuffisamment acidifiĂ©, contaminĂ© par des spores de C. botulinum de type D/C. La quantitĂ© importante dâensilage contaminĂ©e (plus de 20 m3) nâest pas compatible avec la contamination de lâensilage par des spores provenant dâune carcasse piĂ©gĂ©e dans lâensilage. Les spores pourraient provenir dâun tas de fumier de volaille stockĂ© dans la pĂąture avant que lâensilage dâherbe nâait Ă©tĂ© rĂ©alisĂ©, les spores ayant Ă©tĂ© dispersĂ©es dans la pĂąture avant ensilage par le vent ou lâeau de ruissellement. Par ailleurs, la prĂ©sence de carcasses de volailles dans le fumier de volaille est peu probable au vu de la gestion minutieuse des carcasses dans cet Ă©levage, ce qui interroge sur un potentiel portage asymptomatique de C. botulinum de type D/C par les volailles. Ce cas illustre lâimportance des conditions de conservation des ensilages et des conditions de stockage des fumiers de volaille, mĂȘme en cas bonne gestion des cadavres de volaille, pour prĂ©venir lâapparition de foyers de botulisme bovi