OA011-03. Clusterin, a natural ligand of DC-SIGN present in human semen inhibits HIV capture and transmission by dendritic cells

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Design and synthesis of inhibitors of DC-sign mediated infections

DC-SIGN (Dendritic Cell-Specific ICAM-3 Grabbing Nonintegrin) is a C-type (Calcium dependent) lectin, expressed as homotetramers (presenting four copies of a Carbohydrate Recognition Domain (CRD) at the C-terminus) on the surface of immature Dendritic Cells. [1] Dendritic Cells (DCs) areone of the most important class of Antigen Presenting Cells (APCs). They recognize many pathogens through various receptors such as DC-SIGN. After recognition, the pathogen is internalized and DCs mature and migrate to lymph nodes.[2] Then, DCs relay the corresponding processing antigens as MHC complexes to naive T-cells, which differentiate allowing the appropriate immuno-reponse. Some of these pathogens, such as HIV, hijack this mechanism to infect the immune system: they are recognized by DCs but escape the processing pathway. Thus, they can remain “hidden” inside the dendritic cells for many days, being able to reach and infect their target T-cells. The main carbohydrate ligand recognized by DC-SIGN is the high mannose glycan (Man)9(GlcNAc)2 , also known as Man9, a branched oligosaccharide which is presented in multiple copies by several pathogen glycoproteins (gp120, GP1, …). Hence, multivalent mannose display should be an adequate strategy to interact with this lectin with high affinity. In vivo, mannosides are normally hydrolyzed by mannosidases: the use of a structural mimic in place of the natural sugar could avoid an easy degradation in a biological environment. The aim of this project is to design and prepare products that meet these requirements. So far we have demonstrated that the monovalent mimic 1 shown in Figure 1[3] interacts with DC-SIGN (using NMR) and inhibits the DC-SIGN mediated infection in a pseudo-typed Ebola virus model. Moreover, this molecule has been conjugated to a Boltorn-type, leading to neo-glycoconjugates that inhibit the binding of DC-SIGN to gp120 (envelope protein of HIV). In this communication we will report the synthesis of new monovalent inhibitors and the results of their binding assays by SPR. We will show also the synthesis of some multivalent compounds. Acknowledgments. This work was supported by Azioni Integrate Italia-Spagna (IT074ABCCM). [1] T. B. H. Geijtenbeek, , Y. van Kook, et al., Cell 2000, 100, 575-585. [2] Y. van Kooyk, T. B. H. Geijtenbeek, Nat. Rev. Immunol. 2003, 3, 697-709. [3] José J. Reina, Sara Sattin, Donatella Invernizzi, Silvia Mari, Lorena Martínez-Prats, Georges Tabarani, Franck Fieschi, Rafael Delgado, Pedro M. Nieto, Javier Rojo, Anna Bernardi, ChemMedChem , 2007, 2(7),1030-1036

Detection and Quantitative Analysis of Two Independent Binding Modes of a Small Ligand Responsible for DC-SIGN Clustering

DC-SIGN (dendritic cell-specific ICAM-3 grabbing non-integrin) is a C-type lectin receptor (CLRs) present, mainly in dendritic cells (DCs), as one of the major pattern recognition receptors (PRRs). This receptor has a relevant role in viral infection processes. Recent approaches aiming to block DC-SIGN have been presented as attractive anti-HIV strategies. DC-SIGN binds mannose or fucose-containing carbohydrates from viral proteins such as the HIV envelope glycoprotein gp120. We have previously demonstrated that multivalent dendrons bearing multiple copies of glycomimetic ligands were able to inhibit DC-SIGN-dependent HIV infection in cervical explant models. Optimization of glycomimetic ligands requires detailed characterization and analysis of their binding modes because they notably influence binding affinities. In a previous study we characterized the binding mode of DC-SIGN with ligand 1, which shows a single binding mode as demonstrated by NMR and X-ray crystallography. In this work we report the binding studies of DC-SIGN with pseudotrisaccharide 2, which has a larger affinity. Their binding was analysed by TR-NOESY and STD NMR experiments, combined with the CORCEMA-ST protocol and molecular modelling. These studies demonstrate that in solution the complex cannot be explained by a single binding mode. We describe the ensemble of ligand bound modes that best fit the experimental data and explain the higher inhibition values found for ligand

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

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

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

Internet-based medical education: a realist review of what works, for whom and in what circumstances

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