Helminth Glycans at the Host-Parasite Interface and Their Potential for Developing Novel Therapeutics

Helminths are parasitic worms that have successfully co-evolved with their host immune system to sustain long-term infections. Their successful parasitism is mainly facilitated by modulation of the host immune system via the release of excretory-secretory (ES) products covered with glycan motifs such as Lewis X, fucosylated LDN, phosphorylcholine and tyvelose. Evidence is accumulating that these glycans play key roles in different aspects of helminth infection including interactions with immune cells for recognition and evasion of host defences. Moreover, antigenic properties of glycans can be exploited for improving the efficacy of anti-helminthic vaccines. Here, we illustrate that glycans have the potential to open new avenues for the development of novel biopharmaceuticals and effective vaccines based on helminth glycoproteins.

An Embeddable Molecular Code for Lewis X Modification Through Interaction with Fucosyltansferase 9

N-glycans are diversified by a panel of glycosyltransferases in the Golgi, which are supposed to modify various glycoproteins in promiscuous manners, resulting in unpredictable glycosylation profiles in general. In contrast, our previous study showed that fucosyltransferase 9 (FUT9) generates Lewis X glycotopes primarily on lysosome-associated membrane protein 1 (LAMP-1) in neural stem cells. Here, we demonstrate that a contiguous 29-amino acid sequence in the N-terminal domain of LAMP-1 is indispensable for FUT9-dependent Lewis X modification. Interestingly, Lewis X modification was induced on erythropoietin as a model glycoprotein both in vivo and in vitro, just by attaching this sequence to its C-terminus. Based on these results, we conclude that the amino acid sequence from LAMP-1 functions as a “Lewis X code”, which is deciphered by FUT9, and can be embedded into other glycoproteins to evoke a Lewis X modification, opening up new possibilities for protein engineering and cell engineering.

Glycan engineering using synthetic ManNAc analogues enhances sialyl-Lewis-X expression and adhesion of leukocytes

Cell surface glycans, depending on their structures and dynamic modifications, act as the first point of contact and regulate cell-cell, cell-matrix, and cell-pathogen interactions. Particularly, the sialyl-Lewis-X (sLeX, CD15s) tetrasaccharide epitope, expressed on both glycoproteins and gangliosides, participates in leukocyte extravasation via interactions with selectins expressed on endothelial cells, lymphocytes, and platelets (CD62-E/L/P). Neutrophils carrying sLeX epitopes are thought to be responsible for chronic inflammatory diseases resulting in plaque formation and atherosclerosis. Intense efforts have been devoted to the development of sLeX mimetics for inhibition of cell adhesion. On the other hand, dysregulated expression of sLeX and poor extravasation are the major underlying causes of leukocyte adhesion deficiency-II (LAD-II) disorders that result in frequent infections and poor immune response. We hypothesized that metabolic processing of peracetyl N-(cycloalkyl)acyl-D-mannosamine derivatives, through the sialic acid pathway, might result in the expression of sialoglycans with altered hydrophobicity which in-turn could modulate their binding to endogenous lectins, including selectins. Herein, we show that treatment of HL-60 (human acute myeloid leukemia) cells with peracetyl N-cyclobutanoyl-D-mannosamine (Ac4ManNCb), at 50 microM for 48 h, resulted in a robust three to four fold increase in the binding of anti-sLeX (CSLEX1) antibody and enhanced cell adhesion to E-selectin coated surfaces; while the corresponding straight-chain analogue, peracetyl N-pentanoyl-D-mannosamine (Ac4ManNPent), and peracetyl N-cyclopropanoyl-D-mannosamine (Ac4ManNCp) both resulted in 2.0-2.5fold increase compared to controls. The ability to enhance sLeX expression using small molecules has the potential to provide novel opportunities to address challenges in the treatment of immune deficiency disorders.

Glycomic Characterization of Platelets from Patients with Immune Thrombocytopenia

Introduction: Platelet glycoproteins are key contributors to platelet function but their glycans structure is unclear. Alterations in glycan composition have been reported to impact platelet clearance under physiological conditions and in the disease mechanism of immune thrombocytopenia (ITP). Therefore, this study sought to characterize glycan structures in human platelets from healthy control individuals and ITP patients using mass spectrometry (MS)-based glycomics approach, andto compare their glycomic profiles to facilitate understanding of glycan alterations in ITP. Methods: Glycan residues on platelet surface were determined by flow cytometry. Platelet lysates (1×10 8 platelets) from 4 healthy controls and from 4 ITP patients with a clear anomalous glycosylation pattern were characterized by MALDI-MS based glycomic approaches. N-linked glycans were released from platelet glycoproteins by PNGase F digestion and subsequently purified with a Sep-Pak C18 reverse phase cartridge. O-linked glycans were released by reductive elimination. Both pools of glycans were permethylated prior to MALDI-TOF MS to obtain an initial carbohydrate profile. Selected glycan molecular ion species were analyzed by MALDI-TOF-TOF MS/MS before and after digesting with exoglycosidases. Results: Glycans present in platelets from healthy controls and from ITP patients were largely consistent. The MS spectra for N-glycans showed a mixture of high mannose glycans (m/z 1579.8, 1783.9, 1988.0, 2192.1 and 2396.2); complex glycans (m/z 2966.5, 3776.9 and 4587.4); and bisected or truncated glycans (m/z 3211.6 and 4022.1). The spectra showed the presence of bi-, tri- and tetra-antennary complex glycans, which varied in their level of sialylation.Figure 1 shows the relative abundance ratio within eight families of core glycan structures. Platelets from ITP patients showed a consistent increase in desialylated structures such as Hex 5HexNAc 4Fuc 1. In addition to different amounts of attached sialic acid, varying levels of fucosylation were observed; ranging from the addition of a single core Fuc (m/z 2244.1), to the addition of up to three Fuc residues (m/z 3402.7). Collision-activated decomposition (CAD) MALDI-TOF/TOF analysis was performed to generate fragment ions from molecular ions detected in MALDI-TOF profiling for detailed sequencing of platelet N-glycans. This analysis suggested the presence of three isoforms: (i) sialylated tetra-antennary structure with core fucosylation and one Lewis x/a antenna; (ii) sialylated tetra-antennary structure with one Lewis y/b antenna; (ii) sialylated, core-fucosylated tri-antennary structure with one LacNAc extension and one Lewis x/a antenna. Sialidase S digestion was used to highlight the extent of desialylation in the presence of sialidase. Noteworthy, the ratio of non-sialylated bi-and tri-antennary N-glycans in ITP patients were higher than that in controls. This enzymatic digestion confirms the presence of α2,3-linked Neu5Ac on platelet glycans. Remaining sialylated structures may possess α2,6-linked Neu5Ac. O-glycan profiles obtained showed the predominance of core 1 and core 2 structures (Figure 2). The two most dominant glycan structures in core 1 were sialyl T antigen (GalNAc 1Gal 1NeuAc 1; m/z 895.5) and disialyl T antigen (GalNAc 1Gal 1NeuAc 2; m/z 1256.7), being the latter less abundant in ITP patients. The core 2 structure was modified by the addition of fucose and/or sialic acid residues (m/z 1157.7, 1344.8, 1518.9 and 1706.0). Conclusion: N- and O-glycan structures in human platelets were characterized by MALDI-TOF MS profiling to reveal interesting structural features including the presence of sialylLewis x/a epitope, Lewis x/a epitope, Lewis y/b epitope and LacNAc extensions in complex type N-glycans. Presence of terminal sialic acid and sialylLewis x/a on platelet N-glycan antenna also suggest their potentialfunction as ligands for siglecs that are associated with cell signaling functions. Siglec-1 and -2 have been suggested to have potential roles in ethiopathogenesis of autoimmune diseases. Desialylation observed in glycans of platelets from ITP patients, might trigger immune system activation in these patients. This research was funded by ISCIII-Fondos FEDER PI19/00772 and Platelet Disorder Support Association Figure 1 Figure 1. Disclosures Butta: Roche: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; CSL-Behring: Research Funding; Novo-Nordisk: Speakers Bureau. Canales: F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Speakers Bureau; Karyopharm: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; iQone: Honoraria; Sandoz: Honoraria, Speakers Bureau; Incyte: Consultancy; Janssen: Consultancy, Honoraria, Speakers Bureau; Gilead/Kite: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Sanofi: Consultancy; Eusa Pharma: Consultancy, Honoraria; Celgene/Bristol-Myers Squibb: Consultancy, Honoraria. Jiménez-Yuste: Pfizer: Consultancy, Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; BioMarin: Consultancy; Sobi: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Honoraria, Research Funding; Octapharma: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; CSL Behring: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding. Alvarez Román: Octapharma: Consultancy, Honoraria, Research Funding; Biomarin: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Bayer: Consultancy, Honoraria, Research Funding; CSL-Behring: Consultancy, Honoraria, Research Funding; Grifols: Consultancy, Honoraria, Research Funding; Novo-Nordisk: Consultancy, Honoraria, Research Funding; Sobi: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding.

Comprehensive O-GlcNAc glycoproteomics on NOTCH1 EGF repeats refined sequons for O-GlcNAcylation and uncovered unique Lewis X epitopes in mammals

The O-GlcNAc modification of Notch receptors regulates Notch ligand interactions in a manner distinct from other forms of O-glycans on epidermal growth factor-like (EGF) repeats of Notch receptors. Although many proteins, besides Notch receptors, are expected to be O-GlcNAcylated by EGF domain-specific O-GlcNAc transferase (EOGT), only a small number of proteins have been reported to be modified in vivo, and elongated O-GlcNAc glycans have not been extensively explored. To extend our view of the specificity and variety of the glycan modification, we conducted a comprehensive analysis of O-GlcNAc glycans on NOTCH1 in mammals. Mass spectrometric analysis of NOTCH1 fragments expressed in HEK293T cells revealed that several EGF domains with putative O-GlcNAcylation sites were hardly modified with O-GlcNAc. Although amino acid residues before the modification site are preferentially occupied with aromatic residues, Phe and Tyr are preferrable to Trp for the apparent modification with O-GlcNAc. Furthermore, a minor form of fucosylated O-GlcNAc glycans was detected in a subset of EGF domains. Fucosylation of O-GlcNAc glycans was enhanced by FUT1, FUT2, or FUT9 expression. The FUT9-dependent Lewis X epitope was confirmed by immunoblotting using an anti-Lewis X antibody. As expected from the similarity in the glycan structures, the Lexis X antigen was detected on O-fucose glycans. Notably, the Lewis X structure on O-glycans was identified in endogenous NOTCH1 isolated from MCF7 cells. Our results refined the putative consensus sequence for the EOGT-dependent extracellular O-GlcNAc modification in mammals and revealed the structural diversity of functional Notch O-glycans.

Therapeutic Effects of an Anti-sialyl Lewis X Antibody in a Murine Model of Allergic Asthma

Asthma is an allergic disease that causes severe infiltration of leukocytes into the lungs. Leukocyte infiltration is mediated by the binding of sialyl Lewis X (sLex) glycans present on the leukocytes to E-and P-selectins present on the endothelial cells at the sites of inflammation. Here, we found that mouse eosinophils express sLex glycans, and their infiltration into the lungs and proliferation in the bone marrow were significantly suppressed by an anti-sLex monoclonal antibody (mAb) F2 in a murine model of ovalbumin-induced asthma. The percentage of eosinophils in the bronchoalveolar lavage fluid and bone marrow and serum IgE levels decreased significantly in the F2-administered mice. Levels of T helper type 2 (Th2) cytokines and chemokines, involved in IgE class switching and eosinophil proliferation and recruitment, were also decreased in the F2-administered mice. An ex vivo cell rolling assay revealed that sLex glycans mediate the rolling of mouse eosinophils on P-selectin-expressing cells. These results indicate that the mAb F2 exerts therapeutic effects in a murine model of allergen-induced asthma, suggesting that sLex carbohydrate antigen could serve as a novel therapeutic target for allergic asthma.

Chronic kidney disease linked to SARS-CoV-2 infection: a case report

Background The recent COVID-19 pandemic has raised concerns about patient diagnosis and follow-up of chronically ill patients. Patients suffering from chronic illnesses, concomitantly infected by SARS-CoV-2, globally tend to have a worse prognosis and poor outcomes. Renal tropism and acute kidney injury following SARS-CoV-2 infection has recently been described in the literature, with elevated mortality rates. Furthermore, patients with pre-existing chronic kidney disease, infected by SARS-CoV-2, should be monitored carefully. Here, we report the case of a 69-year-old patient with splenic marginal zone lymphoma, suffering from longstanding chronic kidney disease following SARS-CoV-2 infection. Case presentation A 69-year-old male patient previously diagnosed with pulmonary embolism and splenic marginal zone lymphoma (Splenomegaly, Matutes 2/5, CD5 negative and CD23 positive), was admitted to the hospital with shortness of breath, fever and asthenia. A nasopharyngeal swab test was performed in addition to a CT-scan, which confirmed SARS-CoV-2 infection. Blood creatinine increased following SARS-CoV-2 infection at 130 μmol/l, with usual values at 95 μmol/l. The patient was discharged at home with rest and symptomatic medical treatment (paracetamol and hydration), then readmitted to the hospital in August 2020. A kidney biopsy was therefore conducted as blood creatinine levels were abnormally elevated. Immunodetection performed in a renal biopsy specimen confirmed co-localization of SARS-CoV2 nucleocapsid and protease 3C proteins with ACE2, Lewis x and sialyl-Lewis x antigens in proximal convoluted tubules and podocytes. Co-localization of structural and non-structural viral proteins clearly demonstrated viral replication in proximal convoluted tubules in this chronically ill patient. Additionally, we observed the co-localization of sialyl-Lewis x and ACE2 receptors in the same proximal convoluted tubules. Reverse Transcriptase-Polymerase Chain Reaction test performed on the kidney biopsy was negative, with very low Ct levels (above 40). The patient was finally readmitted to the haematology department for initiation of chemotherapy, including CHOP protocol and Rituximab. Conclusions Our case emphasizes on the importance of monitoring kidney function in immunosuppressed patients and patients suffering from cancer following SARS-CoV-2 infection, through histological screening. Further studies will be required to decipher the mechanisms underlying chronic kidney disease and the putative role of sialyl-Lewis x and HBGA during SARS-CoV-2 infection.

Identification of Sialyl-Lewis(x)-Interacting Protein on Human Spermatozoa

Capacitated spermatozoa initiate fertilization by binding to the zona pellucida (ZP). Defective spermatozoa-ZP binding causes infertility. The sialyl-Lewis(x) (SLeX) sequence is the most abundant terminal sequence on the glycans of human ZP glycoproteins involving in spermatozoa-ZP binding. This study aimed to identify and characterize the SLeX-binding proteins on human spermatozoa. By using affinity chromatography followed by mass spectrometric analysis, chromosome 1 open reading frame 56 (C1orf56) was identified to be a SLeX-binding protein of capacitated spermatozoa. The acrosomal region of spermatozoa possessed C1orf56 immunoreactive signals with intensities that increased after capacitation indicating translocation of C1orf56 to the cell surface during capacitation. Treatment with antibody against C1orf56 inhibited spermatozoa-ZP binding and ZP-induced acrosome reaction. Purified C1orf56 from capacitated spermatozoa bound to human ZP. A pilot clinical study was conducted and found no association between the percentage of capacitated spermatozoa with C1orf56 expression and in vitro fertilization (IVF) rate in assisted reproduction treatment. However, the percentage of C1orf56 positive spermatozoa in the acrosome-reacted population was significantly (P < 0.05) lower in cycles with a fertilization rate < 60% when compared to those with a higher fertilization rate, suggesting that C1orf56 may have functions after ZP-binding and acrosome reaction. A larger clinical trial is needed to determine the possible use of sperm C1orf56 content for the prediction of fertilization potential of sperm samples.