DC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule-3-grabbing Non-integrin) is a transmembrane C-type lectin receptor, which plays central part in recognition and internalization of pathogens. It is expressed on antigen-presenting cells (APC), which are called dendritic cells (DC) and plays a fundamental role in activation of immune system. DC-SIGN allows not only to HIV-1 virus to enter DCs, but also to some other microorganisms. Pathogen binding on DC-SIGN triggers intracellular signalization pathways and DC migration to T cells (lymphocytes). Besides binding pathogens, DC-SIGN also binds intercellular adhesion molecules (ICAM)-2 and (ICAM)-3. Both of them are involved in transferring virus HIV-1 to secondary lymphoid organs. In lymphoid tissue HIV-1 virus attacks target CD4+ T cells, where it can replicate. After entering DCs, DC-SIGN transfers pathogens to endosomes and lysosomes, where virus is degradated.
HIV-1 virus causes chronic disease called acquired immune deficiency syndrome (AIDS), which is responsible for millions of deaths. In desire to be able to prevent the disease, different approaches, that inhibit pathogen interaction with DC-SIGN and consequently infection, have been developed. The simplest way to prevent the interaction is the synthesis of small molecules called antagonists. Available crystal structures of DC-SIGN binding site have made the design of these molecules much easier. DC-SIGN binds D-mannose and L-fucose with high affinity. Binding site, where the binding of the ligand depends on the Ca2+, can besides binding the sugar moiety, form additional hydrophobic interactions with the rest of the antagonist. DC-SIGN tetramerization increases binding affinity and avidity. The aim of this master’s thesis is based on the synthesis of monovalent glycoconjugates, which were attached on the selected dendron core. With multimeric presentation we prepared tetramers, which can occupy binding sites of all four DC-SIGN monomers. The synthesized compounds were biologically evaluated in established in vitro system. Final monovalent and tetravalent glycoconjugates were first screened at two different concentrations and then IC50 values were determined for the most active compounds. Monovalent glycoconjugates were active in the micromolar range, while the tetrameric glycoconjugates resulted in dendrons with solubility problems. Namely, dendron compounds were poorly soluble under the assay conditions and hence their activity could not be determined.
|
