Langerin-Heparin Interaction: Two Binding Sites for Small and Large Ligands as revealed by a combination of NMR Spectroscopy and Cross-Linking Mapping Experiments

Langerin is a C-type lectin present on Langerhans cells that mediates capture of pathogens in a carbohydrate-dependent manner, leading to subsequent internalization and elimination in the cellular organelles called Birbeck granules. This mechanism mediated by langerin was shown to constitute a natural barrier for HIV-1 particle transmission. Besides interacting specifically with high mannose and fucosylated neutral carbohydrate structures, langerin has the ability to bind sulfated carbohydrate ligands as 6-sulfated galactosides in the Ca2+ dependent binding site. Very recently langerin was demonstrated to interact with sulfated glycosaminoglycans (GAGs), in a Ca2+ independent way, resulting in the proposal of a new binding site for GAGs. Based on those results, we have conducted a structural study of the interactions of small heparin (HEP) like oligosaccharides with langerin in solution. Heparin-bead cross-linking experiments, an approach specifically designed to identify HEP/HS binding sites in proteins were first carried out and experimentally validated the previously proposed model for the interaction of Lg ECD with 6 kDa HEP. High-resolution NMR studies of a set of 8 synthetic HEP-like trisaccharides harboring different sulfation patterns demonstrated that all of them bound to langerin in a Ca2+ dependent way. The binding epitopes were determined by STD NMR and the bound conformations by transferred NOESY experiments. These experimental data were combined with docking and molecular dynamics and resulted in the proposal of a binding mode characterized by the coordination of calcium by the two equatorial hydroxyl groups OH3 and OH4 at the non-reducing end. The binding also includes the carboxylate group at the adjacent iduronate residue. Such epitope is shared by all the 8 ligands, explaining the absence of any impact on binding from their differences in substitution pattern. Finally, in contrast to the small trisaccharides, we demonstrated that a longer HEP-like hexasaccharide, bearing an additional O-sulfate group at the non-reducing end, which precludes binding to the Ca2+ site, interacts with langerin in the previously identified Ca2+ independent binding site

Usefulness of an Intrapartum Ultrasound Simulator (IUSim™) for Midwife Training: Results from an RCT

Introduction: We conducted a randomized study to determine whether a training session on a dedicated simulator (IUSim™) would facilitate the midwives in learning the technique of transperineal intrapartum ultrasound. Methods: Following a 30-min multimedia presentation including images and videos on how to obtain and measure the angle of progression (AoP) and the head-perineum distance (HPD), 6 midwives with no prior experience in intrapartum ultrasound were randomly split into 2 groups: 3 of them were assigned to the "training group"and 3 to the "control group."The midwives belonging to the former group were taught to measure the 2 sonographic parameters during a 3-h practical session conducted on IUSim™ under the supervision of an expert obstetrician. In the following 3 months, all the 6 midwives were asked to independently perform transperineal ultrasound during their clinical practice and to measure on the acquired images either the AoP or the HPD. The sonographic images were examined in blind by the teaching obstetrician who assigned a 0-3 score to the image quality (IQS) and to the measurement quality (MQS). Results: A total of 48 ultrasound images (24 patients) from 5 midwives were acquired and included in the study analysis. A midwife of the "training group"declined participation after the practical session. Independently from the randomization group, the image quality score (IQS + MQS) was significantly higher for the HPD compared with the AoP (2.5 ± 0.66 vs. 1.79 ± 1.14; p = 0.01). In the training group, the MQS of either AoP (2.66 ± 0.5 vs.1.46 ± 1.45. p = 0.038) and the HPD (2.9 ± 0.33 vs. 1.87 ± 0.83 p = 0.002) was significantly higher in comparison with the control group, while the IQS of both measurements was comparable between the 2 groups (1.91 ± 1.24 vs. 2.25 ± 0.865; p = 0.28). Conclusion: The use of a dedicated simulator may facilitate the midwives in learning how to measure the AoP and the HPD on transperineal ultrasound images

Influence of the reducing-end anomeric configuration of the Man9 epitope on DC-SIGN recognition

High-mannose (Man9GlcNAc2) is the main carbohydrate unit present in viral envelope glycoproteins such as gp120 of HIV and the GP1 of Ebola virus. This oligosaccharide comprises the Man9 epitope conjugated to two terminal N-acetylglucosamines by otherwise rarely-encountered β-mannose glycosidic bond. Formation of this challenging linkage is the bottleneck of the few synthetic approaches described to prepare high mannose. Herein, we report the synthesis of the Man9 epitope with both alpha and beta configurations at the reducing end, and subsequent evaluation of the impact of this configuration on binding to natural receptor of high-mannose, DC-SIGN. Using fluorescence polarization assays, we demonstrate that both anomers bind to DC-SIGN with comparable affinity. These relevant results therefore indicate that the more synthetically-accesible Man9 alpha epitope may be deployed as ligand for DC-SIGN in both in vitro and in vivo biological assays.Ministerio de Economía y Competitividad CTQ2017- 86265-P, PGC2018-099497-B-100, IJCI-2015-2327

Deeply Virtual Compton Scattering off the neutron

The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\vec e},e'\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.Comment: Published in Phys. Rev. Let

The E00-110 experiment in Jefferson Lab's Hall A: Deeply Virtual Compton Scattering off the Proton at 6 GeV

We present final results on the photon electroproduction ($\vec{e}p\rightarrow ep\gamma$) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed resulting in photon electroproduction cross sections at new kinematic settings, for a total of 588 experimental bins. Results of the $Q^2$- and $x_B$-dependences of both the helicity-dependent and helicity-independent cross sections are discussed. The $Q^2$-dependence illustrates the dominance of the twist-2 handbag amplitude in the kinematics of the experiment, as previously noted. Thanks to the excellent accuracy of this high luminosity experiment, it becomes clear that the unpolarized cross section shows a significant deviation from the Bethe-Heitler process in our kinematics, compatible with a large contribution from the leading twist-2 DVCS$^2$ term to the photon electroproduction cross section. The necessity to include higher-twist corrections in order to fully reproduce the shape of the data is also discussed. The DVCS cross sections in this paper represent the final set of experimental results from E00-110, superseding the previous publication.Comment: 48 pages, 32 figure

Scaling Tests of the Cross Section for Deeply Virtual Compton Scattering

We present the first measurements of the \vec{e}p->epg cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q^2 dependence (from 1.5 to 2.3 GeV^2) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q^2. The helicity-independent cross section is also measured at Q^2=2.3 GeV^2. We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation.Comment: 5 pages, 4 figures, 2 tables. Text shortened for publication. References added. One figure remove

Dataset on the RETRO-BMC cruise onboard the R/V Hespérides, April 2017, Brazil-Malvinas Confluence

This dataset, gathered during the RETRO-BMC cruise, reports multiple-scale measurements at the Confluence of the Brazil and Malvinas Currents. The cruise was carried out between 8 and 28 April 2017 onboard R/V Hespérides, departing from Ushuaia and arriving to Santos. Along its track, the vessel recorded near-surface temperature and salinity, as well as the horizontal flow from 20 m down to about 800 m. A total of 33 hydrographic stations were completed in a region off the Patagonian Shelf, within 41.2°S-35.9°S and out to 53.0°W. At each station, a multiparametric probe and velocity sensors were deployed inside the frame of a rosette used to collect water samples at selected depths; these samples were later used for several water analyses, including inorganic nutrient concentrations. Microstructure measurements were carried out in 11 of these hydrographic stations. In addition, two high-resolution three-dimensional surveys were conducted with an instrumented undulating vehicle between 40.6°S-39.0°S and 55.6°W-53.8°W. Lastly, eight high-frequency vertical profilers were deployed in the region and five position-transmitting drifters were launched. These data allow the description of the Confluence from the regional scale to the microscale, and provide a view of the variability of the frontal region on time scales from days to weeks

Exclusive Neutral Pion Electroproduction in the Deeply Virtual Regime

We present measurements of the ep->ep pi^0 cross section extracted at two values of four-momentum transfer Q^2=1.9 GeV^2 and Q^2=2.3 GeV^2 at Jefferson Lab Hall A. The kinematic range allows to study the evolution of the extracted hadronic tensor as a function of Q^2 and W. Results will be confronted with Regge inspired calculations and GPD predictions. An intepretation of our data within the framework of semi-inclusive deep inelastic scattering has also been attempted

Campylobacter infection in adult patients with primary antibody deficiency

International audiencePrimary antibody deficiency (PAD) is characterized by a defective immunoglobulin production and recurrent infections, mostly involving respiratory and gastrointestinal tracts. Chronic or recurrent diarrhea is reported in up to 23%. Campylobacter infection is a common cause of infectious diarrhea, reported in 1.2% to 7.5% of patients with common variable immunodefi-ciency (CVID), the most frequent PAD. The aim of this study was to describe Campylobacter infection in patients with PAD included in a large nationwide study and analyze factors associ-ated with susceptibility to this pathogen. The DEFI (DEFicit Immunitaire) study is an ongoing large cross-sectional French multicentric study of adults with PAD, with retrospective collection of clinical data. All patients with a history of bacteriologically documented Campylobacter infection were identified, and clinical data were collected for each episode. Factors associated with recurrent infection were assessed as oddsratio (OR) and 95% confidence interval (CI), calculated by means of simple regression analysis. In patients with available material, strains of each episode were characterized using molecular analysis and compared (Table E1, available in this article’s Online Repository at www.jaci-inpractice.org). A com-parison of immunodeficiency-related characteristics of patients with and without Campylobacter infection was performed in the homogeneous group of patients with CVID. The control group included patients with CVID from DEFI centers who confirmed that patients did not develop Campylobacter infection after enrollment (Figure E1, available in this article’s Online Repository at www.jaci-inpractice.org). After correction for multiple comparisons, P<.016 was considered significant. Since 2004, 790 patients with PAD were included in the DEFI study, and 51 presented with Campylobacter infection (6.5%). Medical chart was available for review in 45 patients. Characteristics of these patients at the time of enrollment in the DEFI study are detailed in Table E2 (available in this article’s Online Repository at www.jaci-inpractice.org). A total of 97 episodes were recorded (Table I). The overall distribution of Campylobacter species was unremarkable. Antimicrobial susceptibility testing revealed a higher resistance rate than in the general population for each antibiotic tested (see Figure E2, available in this article’s Online Repository at www.jaci-inpractice.org). A comorbidity was present in 55% of Campylobacter episodes, and a coinfection by other enteropathogens in 10%. Most patients were receiving concomitant therapy at the time of episode. One patient with end-stage cirrhosis died with Campylobacter bacteremia. Overall, bacteremia was observed in 24 episodes (13 patients) and was associated with extraintestinal complication in 10 episodes. Nineteen patients (42%) presented with recurrent (2-11) episodes. Factors associated with recurrent episodes were the presence of comorbidity (OR, 3.7 [95% CI, 1.1-13.1]) and undetectable serum IgA (OR, 8.6 [95% CI, 1.1-21.2]). None of these factors remain significant in multivariate analysis. A mo- lecular study of a subset of 18 strains from 5 patients with recurrent infections demonstrated that all strains were different, even when the antimicrobial susceptibility testing was similar and when the episodes occurred closely over time (Figure E3, available in this article’s Online Repository at www.jaci-inpractice.org). Compared with 288 patients with CVID without Campylobacter infection, patients with CVID with Campylo-bacter infection presented a higher prevalence of consanguinity and a more severe CVID phenotype, with more frequent disease- related complications, lower serum immunoglobulin levels, lower B and natural killer (NK) cells, and a trend for lower naive CD4þT cell at the time of enrollment in the DEFI study (Table II). This study is the first description of a large series of patients with PAD and Campylobacter infection. The 6.5% prevalence was probably underestimated because of the retrospective nature of the clinical data collection. In this population, symptoms were mostly restricted to an isolated, frequently severe, chronic watery diarrhea, with associated malnutrition, leading to repeated hospitalizations and impaired quality of life. Other digestive symptoms and fever were less frequent than those observed in the general population. In contrast, bacteremia and extra- digestive localizations were more frequent (25% vs 0.15% to 2%, and 22% vs 7%, respectively). Despite frequent hospitalizations, the overall prognosis was good. Recurrence rate was high (42%) compared with 1.2% in the general population, and was associated with extraintestinal comorbidity and unde- tectable IgA level in univariate analysis. Although limited by the number of available strains, molecular profiles of strains from patients with recurrent infections were all different. Thus, we could hypothesize that reinfection is more likely than persistent colonization, although colonization with multiple strains cannot be excluded. Conditions associated with the occurrence of Campylobacter infection were described in an analysis restricted to a large ho- mogeneous group of 325 patients with CVID. The present data suggest that hypochlorhydria, either proton pump inhibitor (PPI)-induced or associated with autoimmune gastritis, might play an important role in the pathogenesis of this infection. Almost all CVID-associated complications, particularly liver and gastrointestinal disease, were more frequent in patients with Campylobacter infection. A more severe immune deficiency at CVID diagnosis, with a lower serum immunoglobulin level, was also observed. Even in patients with immunoglobulin replacement therapy, IgM and IgA levels remain very low. IgA and IgM, almost absent in immunoglobulin batches, are more important than IgG in Campylobacter immunity. B-cell and specifically switch memory B-cell deficiency was also more severe in patients with CVID with Campylobacter infection than in patients without Campylobacter infection. This is in line with the high prevalence of Campylobacter infection observed in Good syndrome and X-linked agammaglobulinemia, 2 conditions associated with no circulating B cells (Figure E1, available in this article’s Online Repository at www.jaci-inpractice.org). B cells are also known to be important for the dialogue between the immune system and gut microbiota, whose composition is important for Campylobacter immunity. T cells may also play an important role, with a trend for decreased naive T cells. Indeed, 15 patients (40%) presented with a severe associated T-cell defect and could be considered as late-onset combined im-munodeficiency (data not shown). In patients with PAD, Campylobacter infection is quite frequent and seems to be related to various factors adding up together: severity of the immune deficiency, PAD complication, and associated antibiotics, immunosuppressive therapies, and PPI. It is characterized by a high frequency of recurrence and bacteremia. Recurrence is associated with the presence of comorbidity and IgA defect, and turned out to be due to rein- fection more than to persistent colonization, suggesting a specific susceptibility despite immunoglobulin substitution