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Pseudomonas aeruginosa is a Gram‐negative bacterium and an opportunistic pathogen ubiquitously present throughout nature. LecB, a fucose‐, and mannose‐binding lectin, is a prominent virulence factor of P. aeruginosa, which can be expressed on the bacterial surface but also be secreted. However, the LecB interaction with human immune cells remains to be characterized. Neutrophils comprise the first line of defense against infections and their production of reactive oxygen species (ROS) and release of extracellular traps (NETs) are critical antimicrobial mechanisms. When profiling the neutrophil glycome we found several glycoconjugates on granule and plasma membranes that could potentially act as LecB receptors. In line with this, we here show that soluble LecB can activate primed neutrophils to produce high levels of intracellular ROS (icROS), an effect that was inhibited by methyl fucoside. On the other hand, soluble LecB inhibits P. aeruginosa‐induced icROS production. In support of that, during phagocytosis of wild‐type and LecB‐deficient P. aeruginosa, bacteria with LecB induced less icROS production as compared with bacteria lacking the lectin. Hence, LecB can either induce or inhibit icROS production in neutrophils depending on the circumstances, demonstrating a novel and potential role for LecB as an immunomodulator of neutrophil functional responses. [ABSTRACT FROM AUTHOR]

Trained Immunity is defined as a biological process normally induced by exogenous or endogenous insults that triggers epigenetic and metabolic reprogramming events associated with long-term adaptation of innate immune cells. This trained phenotype confers enhanced responsiveness to subsequent triggers, resulting in an innate immune "memory" effect. Trained Immunity, in the past decade, has revealed important benefits for host defense and homeostasis, but can also induce potentially harmful outcomes associated with chronic inflammatory disorders or autoimmune diseases. Interestingly, evidence suggest that the "trainers" prompting trained immunity are frequently glycans structures. In fact, the exposure of different types of glycans at the surface of pathogens is a key driver of the training phenotype, leading to the reprogramming of innate immune cells through the recognition of those glycan-triggers by a variety of glycan-binding proteins (GBPs) expressed by the immune cells. β-glucan or mannose-enriched structures in Candida albicans are some of the examples that highlight the potential of glycans in trained immunity, both in homeostasis and in disease. In this review, we will discuss the relevance of glycans exposed by pathogens in establishing key immunological hubs with glycan-recognizing receptors expressed in immune cells, highlighting how this glycan-GBP network can impact trained immunity. Finally, we discuss the power of glycans and GBPs as potential targets in trained immunity, envisioning potential therapeutic applications. [Display omitted] • Glycans are crucial players in Trained Immunity in homeostasis and disease. • "Memory-like" phenotypes can be induced by glycans exposed by pathogens. • Glycans and Glycan-binding proteins are key regulators of Trained Immunity. • Trained Immunity induced by glycans is a potential therapeutic avenue. [ABSTRACT FROM AUTHOR]

Selective detection of disease-associated changes in the glycocalyx is an emerging field in modern targeted therapies. Detecting minor glycan changes on the cell surface is a challenge exacerbated by the lack of correspondence between cellular DNA/RNA and glycan structures. We demonstrate that multivalent displays of lectins on DNA-barcoded phages-liquid lectin array (LiLA)-detect subtle differences in density of glycans on cells. LiLA constructs displaying 73 copies of diCBM40 (CBM) lectin per virion (φ-CBM 73 ) exhibit non-linear ON/OFF-like recognition of sialoglycans on the surface of normal and cancer cells. A high-valency φ-CBM 290 display, or soluble CBM protein, cannot amplify the subtle differences detected by φ-CBM 73 . Similarly, multivalent displays of CBM and Siglec-7 detect differences in the glycocalyx between stem-like and non-stem populations in cancer. Multivalent display of lectins offer in situ detection of minor differences in glycocalyx in cells both in vitro and in vivo not feasible to currently available technologies., Competing Interests: Declaration of interests R.D. is shareholder of the start-up company 48Hour Discovery Inc. that licensed the patent application (WO2018141058A1) describing LiGA technology., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Glycans decorate all cells and are critical mediators of cellular processes through recognition by glycan-binding proteins (GBPs). While targeting glycan–protein interactions has great therapeutic potential, these interactions are challenging to study as they are generally transient and exhibit low binding affinities. Glycan-based photo-crosslinkable probes have enabled covalent capture and identification of unknown GBP receptors and glycoconjugate ligands. Here, we review recent progress in photo-crosslinking approaches targeting glycan-mediated interactions. We discuss two prominent emerging strategies: 1) development of photo-crosslinkable oligosaccharide ligands to identify GBP receptors; and 2) cell-surface glyco-engineering to identify glycoconjugate ligands of GBPs. Overall, photoaffinity labeling affords valuable insights into complex glycan–protein networks and is poised to help elucidate the glycan–protein interactome, providing novel targets for therapeutic intervention. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The synthesis of glycoprobes based on water-soluble polyacrylamide with a custom content of any low molecular weight fluorescent label is described. The synthesis is carried out in a stepwise manner: in the first step, the polymer is strictly dose-modified with a side substituent-linker containing an amino group; in the second step, the amino group is quantitatively acylated with an activated ester of the dye. The probes are designed to identify and study carbohydrate-binding proteins of plant cells. [ABSTRACT FROM AUTHOR]