ROMP-based Glycopolymers with High Affinity for Mannose-Binding Lectins

Well-defined, highly reactive poly(norbornenyl azlactone)s of controlled length (number-average degree of polymerization D P n ¯ = 10 to 1,000) were made by ring-opening metathesis polymerization (ROMP) of pure exo-norbornenyl azlactone. These were converted into glycopolymers using a facile postpolymerization modification (PPM) strategy based on click aminolysis of azlactone side groups by amino-functionalized glycosides. Pegylated mannoside, heptyl-mannoside, and pegylated glucoside were used in the PPM. Binding inhibition of the resulting glycopolymers was evaluated against a lectin panel (Bc2L-A, FimH, langerin, DC-SIGN, ConA). Inhibition profiles depended on the sugars and the degrees of polymerization. Glycopolymers from pegylated-mannoside-functionalized polynorbornene, with D P n ¯ = 100, showed strong binding inhibition, with subnanomolar range inhibitory concentrations (IC50s). Polymers surpassed the inhibitory potential of their monovalent analogues by four to five orders of magnitude thanks to a multivalent (synergistic) effect. Sugar-functionalized poly(norbornenyl azlactone)s are therefore promising tools to study multivalent carbohydrate-lectin interactions and for applications against lectin-promoted bacterial/viral binding to host cells.

Multivalent glycosystems for human lectins

Human lectins are involved in a wide variety of biological processes, both physiological and pathological, which have attracted the interest of the scientific community working in the glycoscience field. Multivalent glycosystems have been employed as useful tools to understand carbohydrate-lectin binding processes as well as for biomedical applications. The review shows the different scaffolds designed for a multivalent presentation of sugars and their corresponding binding studies to lectins and in some cases, their biological activities. We summarise this research by organizing based on lectin types to highlight the progression in this active field. The paper provides an overall picture of how these contributions have furnished relevant information on this topic to help in understanding and participate in these carbohydrate-lectin interactions.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Low-Valent Calix[4]arene Glycoconjugates Based on Hydroxamic Acid Bearing Linkers as Potent Inhibitors in a Model of Ebola Virus Cis-Infection and HCMV-gB-Recombinant Glycoprotein Interaction with MDDC Cells by Blocking DC-SIGN

In addition to a variety of viral-glycoprotein receptors (e.g., heparan sulfate, Niemann-Pick C1, etc.), dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), from the C-type lectin receptor family, plays one of the most important pathogenic functions for a wide range of viruses (e.g., Ebola, human cytomegalovirus (HCMV), HIV-1, severe acute respiratory syndrome coronavirus 2, etc.) that invade host cells before replication; thus, its inhibition represents a relevant extracellular antiviral therapy. We report two novel p-tBu-calixarene glycoclusters 1 and 2, bearing tetrahydroxamic acid groups, which exhibit micromolar inhibition of soluble DC-SIGN binding and provide nanomolar IC₅₀ inhibition of both DC-SIGN-dependent Jurkat cis-cell infection by viral particle pseudotyped with Ebola virus glycoprotein and the HCMV-gB-recombinant glycoprotein interaction with monocyte-derived dendritic cells expressing DC-SIGN. A unique cooperative involvement of sugar, linker, and calixarene core is likely behind the strong avidity of DC-SIGN for these low-valent systems. We claim herein new promising candidates for the rational development of a large spectrum of antiviral therapeutics.

Polyvalent Transition-State Analogues of Sialyl Substrates Strongly Inhibit Bacterial Sialidases*

Bacterial sialidases (SA) are validated drug targets expressed by common human pathogens such as Streptococcus pneumoniae, Vibrio cholerae, or Clostridium perfringens. Noncovalent inhibitors of bacterial SA capable of reaching the submicromolar level are rarely reported. In this work, multi- and polyvalent compounds are developed, based on the transition-state analogue 2-deoxy-2,3-didehydro-N-acetylneuraminic (DANA). Poly-DANA inhibits the catalytic activity of SA from S. pneumoniae (NanA) and the symbiotic microorganism B. thetaiotaomicron (BtSA) at the picomolar and low nanomolar levels (expressed in moles of molecules and of DANA, respectively). Each DANA grafted to the polymer surpasses the inhibitory potential of the monovalent analogue by more than four orders of magnitude, which represents the highest multivalent effect reported so far for an enzyme inhibition. The synergistic interaction is shown to operate exclusively in the catalytic domain, and not in the flanked carbohydrate-binding module (CBM). These results offer interesting perspectives for the multivalent inhibition of other SA families lacking a CBM, such as viral, parasitic, or human SA.

Say no to drugs: Bioactive macromolecular therapeutics without conventional drugs

The vast majority of nanomedicines (NM) investigated today consists of a macromolecular carrier and a drug payload (conjugated or encapsulated), with a purpose of preferential delivery of the drug to the desired site of action, either through passive accumulation, or by active targeting via ligand-receptor interaction. Several drug delivery systems (DDS) have already been approved for clinical use. However, recent reports are corroborating the notion that NM do not necessarily need to include a drug payload, but can exert biological effects through specific binding/blocking of important target proteins at the site of action. The seminal work of Kopeček et al. on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing biorecognition motifs (peptides or oligonucleotides) for crosslinking cell surface non-internalizing receptors of malignant cells and inducing their apoptosis, without containing any low molecular weight drug, led to the definition of a special group of NM, termed Drug-Free Macromolecular Therapeutics (DFMT). Systems utilizing this approach are typically designed to employ pendant targeting-ligands on the same macromolecule to facilitate multivalent interactions with receptors. The lack of conventional small molecule drugs reduces toxicity and adverse effects at off-target sites. In this review, we describe different types of DFMT that possess biological activity without attached low molecular weight drugs. We classified the relevant research into several groups by their mechanisms of action, and compare the advantages and disadvantages of these different approaches. We show that identification of target sites, specificity of attached targeting ligands, binding affinity and the synthesis of carriers of defined size and ligand spacing are crucial aspects of DFMT development. We further discuss how knowledge in the field of NM accumulated in the past few decades can help in the design of a successful DFMT to speed up the translation into clinical practice.

MCMV Dissemination from Latently-Infected Allografts Following Transplantation into Pre-Tolerized Recipients

Transplantation tolerance is achieved when recipients are unresponsive to donor alloantigen yet mobilize against third-party antigens, including virus. After transplantation, cytomegalovirus (CMV) reactivation in latently-infected transplants reduces allograft viability. To determine if pre-tolerized recipients are resistant to viral dissemination in this setting, we transfused chemically-fixed donor splenocytes (1-ethyl-3- (3′-dimethyl-aminopropyl)-carbo-diimide (ECDI)-treated splenocytes (ECDIsp)) to induce donor antigen tolerance without immunosuppression. In parallel, we implanted donor islet cells to validate operational tolerance. These pre-tolerized recipients were implanted with murine CMV (MCMV) latently-infected donor kidneys (a validated model of CMV latency) to monitor graft inflammation and viral dissemination. Our results indicate that tolerance to donor islets was sustained in recipients after implantation of donor kidneys. In addition, kidney allografts implanted after ECDIsp and islet implantation exhibited low levels of fibrosis and tubulitis. In contrast, kidney cellular and innate immune infiltrates trended higher in the CMV group and exhibited increased markers of CD8⁺ T cell activation. Tolerance induction was unable to prevent increases in MCMV-specific CD8⁺ T cells or dissemination of viral IE-1 DNA. Our data suggest that latently-infected allografts are inherently more susceptible to inflammation that is associated with viral dissemination in pre-tolerized recipients. Thus, CMV latently-infected allografts require enhanced strategies to protect allograft integrity and viral spread.

Molecular Recognition in C-Type Lectins: The Cases of DC-SIGN, Langerin, MGL, and L-Sectin

Carbohydrates play a pivotal role in intercellular communication processes. In particular, glycan antigens are key for sustaining homeostasis, helping leukocytes to distinguish damaged tissues and invading pathogens from healthy tissues. From a structural perspective, this cross‐talk is fairly complex, and multiple membrane proteins guide these recognition processes, including lectins and Toll‐like receptors. Since the beginning of this century, lectins have become potential targets for therapeutics for controlling and/or avoiding the progression of pathologies derived from an incorrect immune outcome, including infectious processes, cancer, or autoimmune diseases. Therefore, a detailed knowledge of these receptors is mandatory for the development of specific treatments. In this review, we summarize the current knowledge about four key C‐type lectins whose importance has been steadily growing in recent years, focusing in particular on how glycan recognition takes place at the molecular level, but also looking at recent progresses in the quest for therapeutics.

Novel trisaccharide based phospholipids as immunomodulators

A focused library of novel mannosylated glycophospholipids was synthesized employing imidate coupling and H-phosphate phosphorylation methods. All novel glycophospholipids were evaluated for their receptor interactions by molecular docking studies. Docking studies revealed dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) specific interaction of the glycophospholipid ligand P4 acts, which was further confirmed by in vitro DC-SIGN expression on monocyte-derived dendritic cells (MoDCs). Further, in vitro and in vivo immunomodulatory activity among the six compounds (P1-P6) examined, compound P4 displayed good immunopotentiation and adjuvant properties as indicated by the induced cytokine expression and enhanced ovalbumin (OVA) specific antibody (IgG) titers. Phosphatidylinositol mannosides (PIMs) analogues in the present study enforced the immunomodulatory properties, truncating parent PIMs or tailor-made of PIMs may bring the novel efficacious molecules, which will be useful in vaccine preparation against different diseases.

Ramified derivatives of 5-(perylen-3-ylethynyl)uracil-1-acetic acid and their antiviral properties

The propargylamide of N3-Pom-protected 5-(perylen-3-ylethynyl)uracil acetic acid, a universal precursor, was used in a CuAAC click reaction for the synthesis of several derivatives, including three ramified molecules with high activities against tick-borne encephalitis virus (TBEV). Pentaerythritol-based polyazides were used for the assembly of molecules containing 2⋯4 antiviral 5-(perylen-3-ylethynyl)uracil scaffolds, the first examples of polyvalent perylene antivirals. Cluster compounds showed enhanced absorbance, however, their fluorescence was reduced due to self-quenching. Due to the solubility issues, Pom group removal succeeded only for compounds with one peryleneethynyluracil unit. Four compounds, including one ramified cluster 9f, showed remarkable 1⋯3 nM EC₅₀ values against TBEV in cell culture.

Ramified clusters of antiviral perylenylethynyl scaffold were prepared using CuAAC reaction of 5-(perylen-3-ylethynyl)-3-pivaloyloxymethyl-1-(propargylamidomethyl)uracil with azides. Compounds inhibited TBEV reproduction at nanomolar concentrations.