Lectin Binding Research Articles

Investigation of the Binding of Lectins with Polymer Glycoconjugates and the Glycoconjugates Containing Silver Nanoparticles by Means of Optical Spectroscopy and Light Scattering.

The synthesis of glycoconjugates, lectin-specific polymers containing a carbohydrate ligand (spacered residue of N-acetyl-D-glucosamine, β-N-Gly-GlcNAc) has been carried out. Glyconanoparticles (glycol-NPs) containing a label detectable by means of spectrophotometry, silver nanoparticles, have been prepared on the basis of the glycoconjugates. Copolymers of maleic anhydride with ethylene or N-vinylpyrrolidone have been used as a carrier to introduce the carbohydrate ligand and a stabilizer of silver nanoparticles. Solutions of the glycoconjugates and the silver glyconanoparticles have been characterized by means of light scattering, UV-visible spectroscopy, and TEM. The interaction of the obtained glycoconjugates and silver glyconanoparticles with N-acetyl-D-glucosamine-specific lectins of Solanum tuberosum agglutinin (STA) and wheat germ agglutinin (WGA) has been investigated by means of light scattering and UV-visible spectro-scopy. The data obtained via these physical methods using the carbohydrate-containing derivatives labeled with silver nanoparticles have been in agreement. It has been shown that the glycoconjugates and silver glyconanoparticles based on more hydrophilic copolymer of maleic acid with N-vinylpyrrolidone are more sensitive than the respective systems based on more hydrophobic copolymer of maleic acid with ethylene. It has been also shown that the considered systems are more sensitive to the STA lectin than to the WGA lectin. The silver glyconanoparticles have allowed more accurate and reliable detection of the lectins by means of light scattering, as compared to the glycopolymer.

Targeting undruggable carbohydrate recognition sites through focused fragment library design

Carbohydrate-protein interactions are key for cell-cell and host-pathogen recognition and thus, emerged as viable therapeutic targets. However, their hydrophilic nature poses major limitations to the conventional development of drug-like inhibitors. To address this shortcoming, four fragment libraries were screened to identify metal-binding pharmacophores (MBPs) as novel scaffolds for inhibition of Ca2+-dependent carbohydrate-protein interactions. Here, we show the effect of MBPs on the clinically relevant lectins DC-SIGN, Langerin, LecA and LecB. Detailed structural and biochemical investigations revealed the specificity of MBPs for different Ca2+-dependent lectins. Exploring the structure-activity relationships of several fragments uncovered the functional groups in the MBPs suitable for modification to further improve lectin binding and selectivity. Selected inhibitors bound efficiently to DC-SIGN-expressing cells. Altogether, the discovery of MBPs as a promising class of Ca2+-dependent lectin inhibitors creates a foundation for fragment-based ligand design for future drug discovery campaigns.

A Bacterial Mannose Binding Lectin as a Tool for the Enrichment of C- and O-Mannosylated Peptides.

Mass spectrometry (MS) easily detects C-mannosylated peptides from purified proteins but not from complex biological samples. Enrichment of specific glycopeptides by lectin affinity prior to MS analysis has been widely applied to support glycopeptide identification but was until now not available for C-mannosylated peptides. Here, we used the α-mannose-specific Burkholderia cenocepacia lectin A (BC2L-A) and show that, in addition to its previously demonstrated high-mannose N-glycan binding capability, this lectin is able to retain C- and O-mannosylated peptides. Besides testing binding abilities to standard peptides, we applied BC2L-A affinity to enrich C-mannosylated peptides from complex samples of tryptic digests of HEK293 and MCF10A whole cell extracts, which led to the identification of novel C-mannosylation sites. In conclusion, BC2L-A enabled specific enrichment of C- and O-mannosylated peptides and might have superior properties over other mannose binding lectins for this purpose.

Overlapping and unique substrate specificities of ST3GAL1 and 2 during hematopoietic and megakaryocytic differentiation

AbstractAlthough the sialyltransferases ST3GAL1 and ST3GAL2 are known to transfer sialic acid to the galactose residue of type III disaccharides (Galβ1,3GalNAc) in vitro, sialylation of O-linked glycosylated proteins in living cells has been largely attributed to ST3GAL1. To examine the role of ST3GAL2 in O-sialylation, we examined its expression during differentiation of human-induced pluripotent stem cells (iPSCs) into hematopoietic progenitor cells (HPCs) and megakaryocytes (MKs). ST3GAL1 and ST3GAL2 each became highly expressed during the differentiation of iPSCs to HPCs but decreased markedly in their expression upon differentiation into MKs, suggesting coordination of expression during megakaryopoiesis. To further delineate their role in these processes, we generated ST3GAL1-, ST3GAL2-, and doubly deficient human iPSC lines. Binding of the peanut agglutinin lectin, which reports the presence of unsialylated Galβ1,3GalNAc glycan chains, was strongly increased in HPCs and MKs derived from double-knockout iPSCs and remained moderately increased in cells lacking either one of these sialyltransferases, demonstrating that both can serve as functional cellular O-glycan sialyltransferases. Interestingly, the HPC markers CD34 and CD43, as well as MK membrane glycoprotein (GP) GPIbα, were identified as major GP substrates for ST3GAL1 and ST3GAL2. In contrast, O-sialylation of GPIIb relied predominantly on the expression of ST3GAL2. Finally, although disruption of ST3GAL1 and ST3GAL2 had little impact on MK production, their absence resulted in dramatically impaired MK proplatelet formation. Taken together, these data establish heretofore unknown physiological roles for ST3GAL1 and ST3GAL2 in O-linked glycan sialylation in hemato- and megakaryocytopoiesis.

Evaluation of Cell Models to Study Monocyte Functions in PMM2 Congenital Disorders of Glycosylation.

Congenital disorders of glycosylation (CDG) are inherited metabolic diseases characterized by mutations in enzymes involved in different steps of protein glycosylation, leading to aberrant synthesis, attachment or processing of glycans. Recently, immunological dysfunctions in several CDG types have been increasingly documented. Despite these observations, detailed studies on immune cell dysfunction in PMM2-CDG and other CDG types are still scarce. Studying PMM2-CDG patient immune cells is challenging due to limited availability of patient material, which is a result of the low incidence of the disease and the often young age of the subjects. Dedicated immune cell models, mimicking PMM2-CDG, could circumvent many of these problems and facilitate research into the mechanisms of immune dysfunction. Here we provide initial observations about the immunophenotype and the phagocytic function of primary PMM2-CDG monocytes. Furthermore, we assessed the suitability of two different glycosylation-impaired human monocyte models: tunicamycin-treated THP-1 monocytes and PMM2 knockdown THP-1 monocytes induced by shRNAs. We found no significant differences in primary monocyte subpopulations of PMM2-CDG patients as compared to healthy individuals but we did observe anomalous surface glycosylation patterns in PMM2-CDG patient monocytes as determined using fluorescent lectin binding. We also looked at the capacity of monocytes to bind and internalize fungal particles and found a slightly increased uptake of C. albicans by PMM2-CDG monocytes as compared to healthy monocytes. Tunicamycin-treated THP-1 monocytes showed a highly decreased uptake of fungal particles, accompanied by a strong decrease in glycosylation levels and a high induction of ER stress. In contrast and despite a drastic reduction of the PMM2 enzyme activity, PMM2 knockdown THP-1 monocytes showed no changes in global surface glycosylation levels, levels of fungal particle uptake similar to control monocytes, and no ER stress induction. Collectively, these initial observations suggest that the absence of ER stress in PMM2 knockdown THP-1 cells make this model superior over tunicamycin-treated THP-1 cells and more comparable to primary PMM2-CDG monocytes. Further development and exploitation of CDG monocyte models will be essential for future in-depth studies to ultimately unravel the mechanisms of immune dysfunction in CDG.

Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology.

Complex asparagine-linked glycosylation plays key roles in cellular functions, including cellular signaling, protein stability, and immune response. Previously, we characterized the appearance of a complex asparagine-linked glycosylated form of lysosome-associated membrane protein 1 (LAMP1) in the cerebellum of Npc1−/− mice. This LAMP1 form was found on activated microglia, and its appearance correlated both spatially and temporally with cerebellar Purkinje neuron loss. To test the importance of complex asparagine-linked glycosylation in NPC1 pathology, we generated NPC1 knock-out mice deficient in MGAT5, a key Golgi-resident glycosyl transferase involved in complex asparagine-linked glycosylation. Our results show that Mgat5−/−:Npc1−/− mice were smaller than Mgat5+/+:Npc1−/− mice, and exhibited earlier NPC1 disease onset and reduced lifespan. Western blot and lectin binding analyses of cerebellar extracts confirmed the reduction in complex asparagine-linked glycosylation, and the absence of the hyper-glycosylated LAMP1 previously observed. Western blot analysis of cerebellar extracts demonstrated reduced calbindin staining in Mgat5−/−:Npc1−/− mice compared to Mgat5+/+:Npc1−/− mutant mice, and immunofluorescent staining of cerebellar sections indicated decreased levels of Purkinje neurons and increased astrogliosis in Mgat5−/−:Npc1−/− mice. Our results suggest that reduced asparagine-linked glycosylation increases NPC1 disease severity in mice, and leads to the hypothesis that mutations in genes involved in asparagine-linked glycosylation may contribute to disease severity progression in individuals with NPC1. To examine this with respect to MGAT5, we analyzed 111 NPC1 patients for two MGAT5 SNPs associated with multiple sclerosis; however, we did not identify an association with NPC1 phenotypic severity.

FC051: Atacicept Reduces Serum ANTI-GD-IGA1 Levels in IgAN Patients

Abstract BACKGROUND AND AIMS Gd-IgA1 plays a central role in IgAN pathogenesis. In IgAN patients, antibodies develop against Gd-IgA1, which then form immune complexes that deposit in the kidney. Increased circulatory levels of autoantigen (Gd-IgA1) or autoantibody (anti-Gd-IgA1) levels correlate with increased risk of progression and worse clinical outcomes. The Ph2a JANUS trial was the first to show substantial serum Gd-IgA1 reduction with atacicept in a randomized clinical trial with IgAN patients. This analysis investigates whether atacicept can also reduce serum anti-Gd-IgA1. METHOD JANUS patients were evaluated for serum anti-Gd-IgA1 at baseline, weeks 4, 12, 24, 48, and 72. An ELISA was developed using as the capture antigen an intact IgA1 paraprotein, which displayed high HPA lectin binding measured Gd-IgA1-specific IgG. Serum samples were normalized using three standard serum samples included on all plates. RESULTS Decrease in serum anti-Gd-IgA1 levels was observed in both atacicept 25- and 75-mg groups over time. At 24 weeks, mean % change from baseline was 24% decrease for atacicept 25 mg and 29% decrease for atacicept 75 mg. At 72 weeks, 28% decrease for atacicept 25 mg and 39% decrease for atacicept 75 mg was observed. Plot of mean % change in serum anti-Gd-IgA1 levels over time is presented in the Figure 1. CONCLUSION Atacicept is the first therapeutic to show a reduction in anti-Gd-IgA1 in IgAN patients. Atacicept’s ability to decrease both circulatory Gd-IgA1 and IgG autoantibodies to this protein, which are central to the pathogenesis and progression of IgAN, supports its potential as a disease modifying therapy for IgAN patients.

Mast cell activation syndrome, Mannose binding lectin, Ehlers-Danlos syndrome, and Neuropsychiatric symptoms. (P17-1.004)

Mast cell activation syndrome, Mannose binding lectin, Ehlers-Danlos syndrome, and Neuropsychiatric symptoms. (P17-1.004)

Human Intelectin-1 Promotes Cellular Attachment and Neutrophil Killing of Streptococcus pneumoniae in a Serotype-Dependent Manner.

Human intelectin-1 (hIntL-1) is a secreted glycoprotein capable of binding exocyclic 1,2-diols within surface glycans of human pathogens such as Streptococcus pneumoniae, Vibrio cholerae, and Helicobacter pylori. For the latter, lectin binding was shown to cause bacterial agglutination and increased phagocytosis, suggesting a role for hIntL-1 in pathogen surveillance. In this study, we investigated the interactions between hIntL-1 and S. pneumoniae, the leading cause of bacterial pneumonia. We show that hIntL-1 also agglutinates S. pneumoniae serotype 43, which displays an exocyclic 1,2-diol moiety in its capsular polysaccharide but is unable to kill in a complement-dependent manner or to promote bacterial killing by peripheral blood mononuclear cells. In contrast, hIntL-1 not only significantly increases serotype-specific S. pneumoniae killing by neutrophils but also enhances the attachment of these bacteria to A549 lung epithelial cells. Taken together, our results suggest that hIntL-1 participates in host surveillance through microbe sequestration and enhanced targeting to neutrophils.

The β‐galactoside binding lectin Galectin regulates metabolism in Drosophila

The β‐galactoside binding lectins, termed galectins, have garnered immense scientific interest for their ability to regulate diverse biologic processes, from adaptive immune responses to epithelial cell biology. Yet, an understanding of the role of galectins in regulating developmental processes has been limited by the functional redundancies across galectins which exist in vertebrates. Thus, we utilized the model organism Drosophila, which contains a single galectin ortholog, to ask what are the developmental requirements for galectins in metazoans. Using CRISPR/Cas9, we generated deletions in the galectin locus which efficiently eliminated galectin protein (Dmgal) across tissues. Intriguing, loss of galectin is not essential in Drosophila as animals ecclose with relatively minimal phenotypes. Among these, dmgal‐deficient animals are significantly smaller than their wild‐type counterparts. Moreover, when challenged to nutrient‐deprivation or Paraquat‐toxicity, dmgal‐deficient animals show marked sensitivity compared to their wild‐type animals. Transcriptomics analysis reveals that dmgal‐deficient animals show significantly different profiles than their wild‐type counterparts, with enrichment in metabolic pathways. Similarly, metabolomics shows distinct profiles from dmgal‐deficient and wild‐type animals with significant alterations in amino acid and nutrient‐sensing pathways. Finally, analysis of the Drosophila fat body reveals alterations in fat content, and tissue specific deletion of galectin in this organ renders animals sensitive to nutrient loss. Taken together, these findings uncover a novel role for dmgal in regulating Drosophila metabolism in the Drosophila fat body, and may provide clues into the role of galectins in regulating insulin sensitivity and NASH/NAFLD in vertebrates.

LMAN1, a Negative Regulator of the Response to House Dust Mite

Abstract We have utilized an unbiased receptor capture approach (CaptiRec) to screen for receptors on dendritic cells which directly bind HDM. Using this technique, we have identified LMAN1 (Lectin, Mannose Binding 1) as a candidate receptor for HDM. LMAN1 is a mannose binding lectin which is primarily known to act as a cargo transporter between the ER, ERGIC, and Golgi compartments. The role played by LMAN1 in the recognition of and response to HDM, is currently unknown. We verify the ability of LMAN1 to directly bind HDM proteins biochemically and in a cellular context. Furthermore, we present evidence to demonstrate that LMAN1 downregulates NF-κB responses in response to inflammatory cytokines and to HDM. Loss of LMAN1 on DCs used for allergic sensitization leads to exacerbated airway inflammation in a HDM model of allergic asthma. Lastly, peripheral DCs of asthmatics show a significant reduction in expression of LMAN1 compared to healthy controls. These findings have potential implications for the development of novel therapeutic interventions for allergy and allergic asthma. Supported by American Lung Association Innovation Award IA-695632

Synthesis of MUC1 Peptide Backbone Bearing Sialyl‐Tn Antigen for Structural and Functional Studies With Endogenous Lectins

ObjectiveTo synthesize the tumor associated analogs of MUC1 for use in structural and functional studies between sialyl‐Tn (sTn) antigen with macrophage galactose‐specific lectin (MGL).AbstractMucin 1 (MUC1) is a heavily glycosylated transmembrane protein, altered in both expression and glycosylation pattern in human carcinomas of the epithelium. The presence of incomplete or truncated glycan structures, often capped by sialic acid, commonly known as tumor‐associated carbohydrate antigens (TACAs), on the cell surface is a well‐known cancer biomarker. Accumulating evidence suggests that TACAs expression is associated with tumor escape from immune defenses through interaction with endogenous carbohydrate binding proteins (lectins). These interactions often lead to creation of a protumor microenvironment, favoring tumor initiation, progression, metastasis, and immune evasion. Macrophage galactose binding lectin (MGL) is a C‐type lectin receptor found on antigen‐presenting cells (APCs) which facilitates the uptake of carbohydrate antigens for antigen presentation, modulating the immune response homeostasis, autoimmunity, and cancer. Considering the crucial role of tumor‐associated forms of MUC1 with MGL in tumor immunology, a thorough understanding of this interaction is essential for it to be exploited for cancer vaccine strategies. The specific aim of this research is to synthesize structurally well‐defined chemical probes, mono and multiple glycosylated MUC1 glycopeptide models carrying the Tn or sTn, that allow for the control of the complexity of the chemical space of the multivalent ligands. For this purpose, a concise scheme was developed for the large synthesis of the sTn antigen building block. Thiophenyl glycoside donors, in the presence TfOH/NIS or TMSOTf/NIS as promoter system, were used for the galactosylation and sialylation steps of the amino acid building block synthesis, respectively. We explored the effect of activator, temperature, solvent, and excess equivalent of sialic acid thioglycoside donor on sialylation reaction. The most favorable reaction conditions improved the desired α‐stereoselectivity, decreased the competing 2,3‐elimination reaction on the sialyl donor during activation, leading to overall increase in the reaction yield. This building block was used in the stepwise solid‐phase peptide synthesis of MUC1 glycopeptide models. The secondary structure of synthesized peptides was determined by circular dichroism (CD) spectroscopy.

Lectins as Biomarkers of IC/BPS Disease: A Comparative Study of Glycosylation Patterns in Human Pathologic Urothelium and IC/BPS Experimental Models.

Pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS) remains poorly understood, as well as its effective diagnosis and therapy. Studying changes in tissue glycosylation patterns under pathological conditions is a promising way of discovering novel biomarkers and therapeutic targets. The glycobiology of IC/BPS is largely understudied, therefore we compared glycosylation patterns of normal human urothelium with the urothelium of IC/BPS patients using a selection of 10 plant-based lectins with different monosaccharide preferences. We also compared lectin binding to human urothelium with the two most cited experimental models of IC/BPS, specifically, TNFα-treated human urothelial cell line RT4 and cyclophosphamide-induced chronic cystitis in C57BL6/J mice. Furthermore, binding of four of the selected lectins (ConA, DSL, Jacalin and WGA) was evaluated qualitatively by means of fluorescence microscopy, and quantitatively by fluorescence intensity (F.I.) measurements. Our results reveal a significant reduction in F.I. of Jacalin, as well as a prominent change in the WGA labeling pattern in the urothelium of IC/BPS patients, suggesting their potential use as promising additional biomarkers for histopathological diagnosis of IC/BPS. We have also shown that urothelial glycosylation patterns between selected experimental models and patients with IC/BPS are similar enough to offer an adequate platform for preclinical study of IC/BPS glycobiology.

Definition of IgG Subclass-Specific Glycopatterns in Idiopathic Membranous Nephropathy: Aberrant IgG Glycoforms in Blood

The podocyte injury, and consequent proteinuria, that characterize the pathology of idiopathic membranous nephropathy (IMN) is mediated by an autoimmune reaction against podocyte antigens. In particular, the activation of pathways leading to abundant renal deposits of complement is likely to involve the binding of mannose-binding lectin (MBL) to aberrant glycans on immunoglobulins. To obtain a landscape of circulatory IgG Fc glycosylation characterizing this disease, we conducted a systematic N-glycan profiling study of IgG1, 2, and 4 by mass spectrometry. The cohort included 57 IMN patients, a pathological control group with nephrotic syndrome (PN) (n = 20), and 88 healthy control subjects. The effect of sex and age was assessed in all groups and controlled by rigorous matching. Several IgG Fc glycan traits were found to be associated with IMN. Interestingly, among them, only IgG4-related results were specific for IMN and not for PN. Hypo-galactosylation of IgG4, already shown for IMN, was observed to occur in the absence of core fucose, in line with a probable increase of pro-inflammatory IgG. In addition, elevated levels of fucosylated IgG4, along with low levels of hybrid-type glycans, were detected. Some of these IgG4 alterations are likely to be more pronounced in high PLA2R (phospholipase A2 receptor) patients. IgG Fc glycosylation patterns associated with IMN warrant further studies of their role in disease mechanisms and may eventually enrich the diagnostic spectrum regarding patient stratification.

The myrosinase-glucosinolate system to generate neoglycoproteins: A case study targeting mannose binding lectins

A convenient strategy for a ‘one-pot’ synthesis of neoglycoproteins (NGP) was developed using the myrosinase-glucosinolate couple, a natural enzyme-substrate system. This enzymatic reaction allowed us to generate an isothiocyanate in situ which then reacted with the lysine residues of bovine serum albumin protein (BSA) to produce multivalent neoglycoproteins. Using two models, glucomoringin which is a natural glucosinolate bearing a l-rhamnose unit, and an artificial glucosinolate specifically designed for mannose type lectins, an average of up to 17.8 and 28.7 carbohydrate residues could be respectively grafted onto the BSA protein. This process is comparable to commercial approaches using BSA-ManC without the disadvantage of handling harmful chemical reagents. Lectin binding screening (GLYcoPROFILE®) showed that among all NGPs synthesized, BSA-Man 16 gave similar and in some cases better affinities in comparison with commercial BSA-Manc towards various mannose-specific lectins.

CHARACTERIZATION OF GLYCOCUNJUGATE DISTRIBUTION IN THE EPIDIDYMIS OF THE JAVAN MUNTJACS (Muntiacus muntjak muntjak)

The presence of glycoconjugates in caput, corpus, and cauda epididymis of the Javan muntjacs was performed using lectin histochemical method. The epididymis organs were obtained from two adult male Javan muntjacs in hard antler stage and then immediately fixed in Bouin’s solution and processed in histological manner. Six types of biotinylated lectins namely Peanut agglutinin (PNA), Soybean agglutinin (SBA), Wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA), Concanavalin A (Con A), and Ulex europaeus agglutinin I (UEA I) were applied to detect the specific glycoconjugates in the epididymal tissue of muntjacs. The result showed the presence of glycoconjugates were detected by five types of lectins except UEA I in caput, corpus, and cauda epididymis with specific distribution and also the intensity of lectins binding. Glycoconjugates β-galactose, β-glucose, mannose, N-acetyl-galactosamine, N-acetyl-glucosamine, and sialic acid were stained with various intensity in epithelial cells, basal cells, stereocilia, spermatozoa, and stroma of caput, corpus, and cauda epididymis. The presence of sialic acid on the surface of spermatozoa detected by WGA are thought to be play a role on sperm protection during their maturation and transit along epididymal lumen. In conclusion, the difference of glycoconjugates distribution pattern and lectin binding in the epididymal caput, corpus, and cauda of the Javan muntjac indicates the regional differences in epididymal function in spermatozoa maturation.

Galectin-3 Mitigates Cardiomyocytes Injury through Modulation of Left Ventricular Cathepsins B, D, L and S at 24-Hour Post Myocardial Infarction.

Galectin 3 (GAL-3) is a beta galactoside binding lectin that has different roles in normal and pathophysiological conditions. GAL-3 was found to be up regulated in animal models of myocardial infarction (MI). Cathepsins are intracellular lysosomal proteases that degrade proteins. The objective of his study is to investigate if high GAL-3 after myocardial infarction has a protective role on the heart through its modulation of lysosomal Cathepsins in ischemic myocardium. Male C57B6/J mice and GAL-3 knockout (KO) mice were used for permanent ligation of the left anterior descending artery of the heart to create infarction in the anterior myocardium. Hearts and plasma samples were collected 24 hours after the induction of MI and were used for enzyme linked immunosorbent assay and immunofluorescent staining. Our results show that the significant increase in GAL-3 levels in the left ventricle at 24-hour following MI is associated with significant lower levels of cathepsins B, D, L and S in GAL-3 wild MI group than GAL-3 KO MI group. We also report a significant lower plasma level of Troponin I in GAL-3 wild MI group than GAL-3 KO MI group. The increased levels of GAL-3 at 24-hour following MI regulates the process of cardiomyocytes injury through modulation of lysosomal cathepsins B, D, L and S.

Photoswitching Affinity and Mechanism of Multivalent Lectin Ligands

Multivalent receptor–ligand binding is a key principle in a plethora of biological recognition processes. Immense binding affinities can be achieved with the correct spatial orientation of the ligands. Accordingly, the incorporation of photoswitches, which can be used to reversibly change the spatial orientation of molecules, into multivalent ligands is a means to alter the binding affinity and possibly also the binding mode of such ligands. We report a divalent ligand for the model lectin wheat germ agglutinin (WGA) containing an arylazopyrazole photoswitch. This switch, which has recently been introduced as an alternative to the more commonly used azobenzene moiety, is characterized by almost quantitative E/Z photoswitching in both directions, high quantum yields, and high thermal stability of the Z isomer. The ligand was designed in a way that only one of the isomers is able to bridge adjacent binding sites of WGA leading to a chelating binding mode. Photoswitching induces an unprecedentedly high change in lectin binding affinity as determined by isothermal titration calorimetry (ITC). Furthermore, additional dynamic light scattering (DLS) data suggest that the binding mode of the ligand changes from chelating binding of the E isomer to crosslinking binding of the Z isomer.

Serologic response to a third dose of an mRNA-based SARS-CoV-2 vaccine in lung transplant recipients

Lung transplant recipients have an increased risk for severe coronavirus disease 2019 (COVID-19) due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A third dose of a SARS-CoV-2 vaccine has been recommended for all solid organ transplant recipients, but data from lung transplant recipients specifically are scarce. In this study, the serologic response to a third dose of an mRNA-based SARS-CoV-2 vaccine was measured in 78 lung transplant recipients. Sixty-two percent (n = 48) had a serological response to vaccination, which was significantly higher than after the second vaccine dose (27 patients (35%); p = 0.0013). A positive serologic response was associated with having had COVID-19 (p = 0.01), and higher serum IgG level and complement mannose binding lectin pathway activity prior to vaccination (p = 0.04 and p = 0.03, respectively). Serologic response was not associated with the dose of mycophenolate mofetil or prednisone or other immune status parameters. Eleven patients (14%) developed COVID-19 after the second or third vaccine dose, but this did not associate with serologic response after the second vaccine dose (9% in patients who developed COVID-19 versus 39% in patients who did not develop COVID-19 (p = 0.09)), or with serologic response above cut-off values associated with clinical protection in previous studies. In conclusion, the response to mRNA-based SARS-CoV-2 vaccines in lung transplant recipients improves significantly after a third vaccine dose. Factors associated with a positive serologic response are having had COVID-19 prior to vaccination, and serum IgG and complement mannose binding lectin pathway activity prior to vaccination. Serologic response did not associate with clinical protection against COVID-19 in this study.

Mannose binding lectin defects and autoimmune diseases

Mannose binding lectin defects and autoimmune diseases