Pseudosaccharide functionalized dendrimers as potent inhibitors of DC-SIGN dependent Ebola pseudotyped viral infection.

The development of compounds with strong affinity for the receptor DC-SIGN is a topic of remarkable interest due to the role that this lectin plays in several pathogen infection processes and in the modulation of the immune response. DC-SIGN recognizes mannosylated and fucosylated oligosaccharides in a multivalent manner. Therefore, multivalent carbohydrate systems are required to interact in an efficient manner with this receptor and compete with the natural ligands. We have previously demonstrated that linear pseudodi- and pseudotrisaccharides are adequate ligands for DC-SIGN. In this work, we show that multivalent presentations of these glycomimetics based on polyester dendrons and dendrimers lead to very potent inhibitors (in the nanomolar range) of cell infection by Ebola pseudotyped viral particles by blocking DC-SIGN receptor. Furthermore, SPR model experiments confirm that the described multivalent glycomimetic compounds compete in a very efficient manner with polymannosylated ligands for binding to DC-SIGN.

Benzothiadiazole (BTH) activates sterol pathway and affects vitamin D3 metabolism in Solanum malacoxylon cell cultures.

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a particularly efficient inducer of systemic acquired resistance (SAR), was developed as an immunizing agent to sensitize various crop species against pathogen infections. Recent works highlighted its activating effect on different metabolic pathways, concerning both primary and secondary metabolites. In this study, we investigated the effect of BTH treatment on sterol levels and vitamin D(3) metabolism in Solanum malacoxylon cultures. Calli of S. malacoxylon were incubated in Gamborg B5 liquid medium alone or added with 50 µM BTH for different times (one, two or three cycles of light). Histocytochemical investigations performed on our experimental system using 3,3'-diaminobenzidine (DAB) for hydrogen peroxide (H(2)O(2)) detection and phloroglucinol for lignin staining showed that BTH causes H(2)O(2) accumulation and lignin deposition in treated calli. Gas chromatographic analysis of principal cell membrane sterols (ß-sitosterol, campesterol, stigmasterol) showed that BTH transiently increases their cellular levels. Callus cultures were found to contain also cholesterol, 7-dehydrocholesterol, the putative precursor of vitamin D(3), and the hydroxylated metabolites 25-hydroxyvitamin D(3) [25(OH)D(3)] and 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)]. BTH treatment enhanced 7-dehydrocholesterol while reduced cholesterol. HPLC analysis of sample extracts showed that BTH does not affect the cell content of vitamin D(3), though results of ELISA tests highlighted that this elicitor moderately enhances the levels of 25(OH)D(3) and 1α,25(OH)(2)D(3) metabolites. In conclusion, BTH treatment not only causes cell wall strengthening, a typical plant defence response, as just described in other experimental models, but in the same time increases the cellular level of the main sterols and 7-dehydrocholesterol.

A multivalent inhibitor of the DC-SIGN dependent uptake of HIV-1 and Dengue virus.

DC-SIGN is a C-type lectin receptor on antigen presenting cells (dendritic cells) which has an important role in some viral infection, notably by HIV and Dengue virus (DV). Multivalent presentation of carbohydrates on dendrimeric scaffolds has been shown to inhibit DC-SIGN binding to HIV envelope glycoprotein gp120, thus blocking viral entry. This approach has interesting potential applications for infection prophylaxis. In an effort to develop high affinity inhibitors of DC-SIGN mediated viral entry, we have synthesized a group of glycodendrimers of different valency that bear different carbohydrates or glycomimetic DC-SIGN ligands and have studied their DC-SIGN binding activity and antiviral properties both in an HIV and a Dengue infection model. Surface Plasmon Resonance (SPR) competition studies have demonstrated that the materials obtained bind efficiently to DC-SIGN with IC50s in the µm range, which depend on the nature of the ligand and on the valency of the scaffold. In particular, a hexavalent presentation of the DC-SIGN selective antagonist 4 displayed high potency, as well as improved accessibility and chemical stability relative to previously reported dendrimers. At low µm concentration the material was shown to block both DC-SIGN mediated uptake of DV by Raji cells and HIV trans-infection of T cells.

Inhibition of DC-SIGN-mediated HIV infection by a linear trimannoside mimic in a tetravalent presentation.

HIV infection is pandemic in humans and is responsible for millions of deaths every year. The discovery of new cellular targets that can be used to prevent the infection process represents a new opportunity for developing more effective antiviral drugs. In this context, dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN), a lectin expressed at the surface of immature dendritic cells and involved in the initial stages of HIV infection, is a promising therapeutic target. Herein we show the ability of a new tetravalent dendron containing four copies of a linear trimannoside mimic to inhibit the trans HIV infection process of CD4+ T lymphocytes at low micromolar range. This compound presents a high solubility in physiological media, a neglectable cytotoxicity, and a long-lasting effect and is based on carbohydrate-mimic units. Notably, the HIV antiviral activity is independent of viral tropism (X4 or R5). The formulation of this compound as a gel could allow its use as topical microbicide.