Design and synthesis of nanoparticles functionalised with Lewis oligosaccharides for selective targeting of DC-SIGN
Keywords: DC-SIGN
NANOPARTICLE
SUGAR CHEMISTRY
DENDRITIC CELL
MRI
VACCINE DEVELOPMENT
LEWIS OLIGOSACCHARIDES
CARBOHYDRATE
IN VIVO TARGETING
OLIGOSACCHARIDE SYNTHESIS
SURFACE MODIFICATION
ORGANIC SYNTHESIS

Dendritic cells (DC) are one of the major antigen presenting cells (APC) of the body. They, by capture of antigen and cross-presentation of these antigens, activate dormant T-cells and co-activate B-cells. As such they regulate the immune system toward either a more humoral type immune response or a more cellular type immune response. These properties have made them very studied over the past decade and many works have focus on the development of vaccine or therapeutic using DCs as a target. However, most of these actual studies have been done by injection of in vitro pre-activated DCs. The major drawback of this technique is the use of non-natural and non individual specific DCs (monocytes derived DCs and/or stem cells DCs). That is why therapeutic carrier targeting specifically DCs has to be developed. To achieve this goal, specific molecules present at the surface of DCs and involved in the activation of the immune system has to be targeted. Among them, DC-Specific ICAM-3 Grabbing Non-integrin CD209 (DC-SIGN) is very specifically expressed only on one subset of DCs called interstitial DCs. This lectin has been proven to be one of the first contacts of the DCs with T-cells and to induce one major interaction for cells proliferation of dormant T-cells.
The goal of the project is to design a probe that can be used in vivo and post-mortem to target DCs via DC-SIGN. Therefore, we can use these particles as a proof of concept in vivo and in vitro, record the immune response obtained with them in vivo and in vitro and design probes that can be used to induce specific immune response for future therapy development.
Lewis sugars have been shown to be quite specific to DC-SIGN. Their syntheses have been carried out in our lab with a cyanomethylthio linker at their anomeric position. This linker, once activated as a 2-imino-2-methoxyethyl moiety, has permitted the attachment of the oligosaccharides at the surface of dextran-coated iron oxide MRI nanoparticle. These particles have been chosen for their powerful properties and the advantage of the technique they are used for. Indeed, as particles their sizes mimic pathogens and DCs would interact with them, as they will with pathogen. Moreover, many copies of each oligosaccharide could be attached at their surface enhancing the interaction of the particles with the targeted lectin via a multivalent effect. As a technique, MRI has the advantage to be recorded over a long period of time (compare to 18F PET for example), with a relatively low signal/noise ratio (compare to fluorescence techniques) and without being harmful. FITC fluorescent Lewis X nanoparticles have been actually design and characterised (size by DLS, number of sugar by particles by ICP or fluorescamine fluorescence assay and binding affinity by ELISA with DC-SIGN-Fc). They have been first tested in vitro with models cells (Raji and monocytes derived DCs) for specific uptake assays, where they exhibit specific uptake and internalisation. Lewis-x nanoparticles have also been tested in vivo in a rat model and have been shown to be retained in Lymph nodes compared to control particles. Post mortem analysis appears to demonstrate that these particles were internalised by rat DCs and transported in the centre of the lymph node known as the T-cell region.
Finally, cytokines and CD86 concentration measurement have shown that upon internalisation of the nanoparticles, DC maturated. In addition, an antigenic OVA peptide epitope was attached to the surface of the nanoparticles for future T-cell proliferation experiments. It will allow the determination of the immune response expected.
In summary, we have developed an immunogenic MRI-active probe that can target specifically DC-SIGN via the interaction with Lewis antigens present at the surface of the probe and trigger DC maturation.