Characterisation of the Dynamic Interactions between Complex N-Glycans and Human CD22.

CD22 (Siglec-2) is a B-cell surface inhibitory protein capable of selectively recognising sialylated glycans, thus dampening autoimmune responses against self-antigens. Here we have characterised the dynamic recognition of complex-type N-glycans by human CD22 by means of orthogonal approaches including NMR spectroscopy, computational methods and biophysical assays. We provide new molecular insights into the binding mode of sialoglycans in complex with h-CD22, highlighting the role of the sialic acid galactose moieties in the recognition process, elucidating the conformational behaviour of complex-type N-glycans bound to Siglec-2 and dissecting the formation of CD22 homo-oligomers on the B-cell surface. Our results could enable the development of additional therapeutics capable of modulating the activity of h-CD22 in autoimmune diseases and malignancies derived from B-cells.

Minimizing the Entropy Penalty for Ligand Binding: Lessons from the Molecular Recognition of the Histo Blood-Group Antigens by Human Galectin-3.

Ligand conformational entropy plays an important role in carbohydrate recognition events. Glycans are characterized by intrinsic flexibility around the glycosidic linkages, thus in most cases, loss of conformational entropy of the sugar upon complex formation strongly affects the entropy of the binding process. By employing a multidisciplinary approach combining structural, conformational, binding energy, and kinetic information, we investigated the role of conformational entropy in the recognition of the histo blood-group antigens A and B by human galectin-3, a lectin of biomedical interest. We show that these rigid natural antigens are pre-organized ligands for hGal-3, and that restriction of the conformational flexibility by the branched fucose (Fuc) residue modulates the thermodynamics and kinetics of the binding process. These results highlight the importance of glycan flexibility and provide inspiration for the design of high-affinity ligands as antagonists for lectins.

Glycomimetics Targeting Glycosyltransferases: Synthetic, Computational and Structural Studies of Less-Polar Conjugates.

The Leloir donors are nucleotide sugars essential for a variety of glycosyltransferases (GTs) involved in the transfer of a carbohydrate to an acceptor substrate, typically a protein or an oligosaccharide. A series of less-polar nucleotide sugar analogues derived from uridine have been prepared by replacing one phosphate unit with an alkyl chain. The methodology is based on the radical hydrophosphonylation of alkenes, which allows coupling of allyl glycosyl compounds with a phosphate unit suitable for conjugation to uridine. Two of these compounds, the GalNAc and galactose derivatives, were further tested on a model GT, such as GalNAc-T2 (an important GT widely distributed in human tissues), to probe that both compounds bound in the medium-high micromolar range. The crystal structure of GalNAc-T2 with the galactose derivative traps the enzyme in an inactive form; this suggests that compounds only containing the ß-phosphate could be efficient ligands for the enzyme. Computational studies with GalNAc-T2 corroborate these findings and provide further insights into the mechanism of the catalytic cycle of this family of enzymes.

Computational Approaches to Toll-Like Receptor 4 Modulation.

Toll-like receptor 4 (TLR4), along with its accessory protein myeloid differentiation factor 2 (MD-2), builds a heterodimeric complex that specifically recognizes lipopolysaccharides (LPS), which are present on the cell wall of Gram-negative bacteria, activating the innate immune response. Some TLR4 modulators are undergoing preclinical and clinical evaluation for the treatment of sepsis, inflammatory diseases, cancer and rheumatoid arthritis. Since the relatively recent elucidation of the X-ray crystallographic structure of the extracellular domain of TLR4, research around this fascinating receptor has risen to a new level, and thus, new perspectives have been opened. In particular, diverse computational techniques have been applied to decipher some of the basis at the atomic level regarding the mechanism of functioning and the ligand recognition processes involving the TLR4/MD-2 system at the atomic level. This review summarizes the reported molecular modeling and computational studies that have recently provided insights into the mechanism regulating the activation/inactivation of the TLR4/MD-2 system receptor and the key interactions modulating the molecular recognition process by agonist and antagonist ligands. These studies have contributed to the design and the discovery of novel small molecules with promising activity as TLR4 modulators.

Incidence of pneumococcal disease from 2003 to 2019 in children ≤17 years in England.

BACKGROUND: Pneumococcal disease is a leading cause of communicable disease morbidity and mortality globally. We aimed to estimate invasive pneumococcal disease (IPD), pneumococcal pneumonia (PP) and all-cause pneumonia (ACP) incidence rates (IRs) in children aged 0-17 years in England from 2003 to 2019. METHODS: A retrospective study in children ≤17 years old from 2003 to 2019 using the Clinical Practice Research Datalink (CPRD) Gold and Hospital Episodes Statistics Admitted Patient Care (HES APC) databases. IPD episodes were identified in hospital records (HES APC). PP (caused by Streptococcus pneumoniae only) and ACP episodes (caused by any pathogen) were identified in primary care (CPRD) and in hospital records (HES APC). Annual IRs by age-group were calculated as the number of episodes/person-years (PY) at risk, with 95% confidence intervals (95% CI). Interrupted time series analyses were conducted to assess changes in IRs across the post-PCV7 (2007-2009), early post-PCV13 (2011-2014) and late post-PCV13 (2015-2019) periods compared to the pre-PCV7 period (2003-2005) using generalized linear models. RESULTS: 170 IPD episodes, 769 PP episodes and 12,142 ACP episodes were identified in 1,500,686 children in 2003-2019. The overall IPD, PP and ACP IRs (per 100,000 PY) were 2.29 (95% CI 1.96-2.66), 10.34 (95% CI 9.62-11.10) and 163.37 (95% CI 160.47-166.30), respectively. The highest IPD, PP and ACP IRs were observed in children aged < 2 years compared to older children (2-4 and 5-17 years). IPD IRs decreased between the pre-PCV7 period and the late post-PCV13 period from 3.28 (95% CI 2.42-4.33) to 1.41 (95% CI 0.80-2.29), IRR 0.28 (95% CI 0.09-0.90), p-value 0.033. PP IRs declined between the pre-PCV7 period and the late post-PCV13 period from 14.65 (95% CI 12.77-16.72) to 3.87 (95% CI 2.81-5.20), IRR 0.19 (95% CI 0.09-0.38), p-value < 0.001. ACP IRs declined between the pre-PCV7 period and the late post-PCV13 period from 167.28 (95% CI 160.78-173.96) to 124.96 (95% CI 118.54-131.63), IRR 0.77 (95% CI 0.66-0.88), p-value < 0.001. CONCLUSIONS: The clinical burden of IPD, PP and ACP declined in children in England aged 0-17 years between 2003 and 2019, especially in the late post-PCV13 period. This study highlights the importance of PCV vaccination in reducing the burden of PD and ACP in children in England.

Real-World Persistence and Treatment Patterns in Patients with Psoriatic Arthritis Treated with Anti-IL17 Therapy in Spain: The PerfIL-17 Study.

INTRODUCTION: Given the growing interest and use of interleukin-17 inhibitors (anti-IL17) for the treatment of psoriatic arthritis (PsA), an observational study has been conducted to characterize the patient profile, treatment patterns, and persistence of ixekizumab or secukinumab in patients with PsA receiving them as first anti-IL17. METHODS: This is a multicenter retrospective study, conducted at eight Spanish hospitals where data from adult patients with PsA were collected from electronic medical records. Three cohorts of patients, initiating treatment with an anti-IL17 [secukinumab 150 mg (SECU150), secukinumab 300 mg (SECU300), or ixekizumab (IXE)] between January 2019 and March 2021, were included. Demographic and clinical patient characteristics, treatment patterns, and persistence were analyzed descriptively. Continuous data were presented as mean [standard deviation (SD)] and categorical variables as frequencies with percentages. Persistence rates at 3, 6, and 12 months were calculated. RESULTS: A total of 221 patients with PsA were included in the study [SECU150, 103 (46.6%); SECU300, 38 (17.2%); and IXE, 80 (36.2%)]. Treatment patterns differed by clinical characteristics: SECU150 was initiated more frequently in patients with moderate PsA and less peripheral joint involvement, while patients on SECU300 included those with a higher rate of enthesitis and active skin psoriasis, and patients on IXE showed a longer time since PsA diagnosis, more frequent comorbidities, joint involvement, and diagnosed skin psoriasis. Conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) were previously administered in 88.2% of patients and biologic or targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs) were administered in 72.9%. The mean number of previous b/tsDMARDs was 2.4 (SD 1.5) in the IXE cohort, 1.7 (SD 0.9) in the SECU300 cohort, and 1.6 (SD 1.0) for those in the SECU150 cohort. The global persistence on all anti-IL17 was 97.2%, 88.4%, and 81.0% at 3, 6, and 12 months, respectively. The most frequent reason for discontinuation across the three cohorts was lack of effectiveness (16.7%; 37/221). CONCLUSIONS: Most of the patients with PsA treated with anti-IL17 in Spain had moderate to severe disease activity, high peripheral joint and skin involvement, and had received previous b/tsDMARDs. More than 80% of patients with a 1-year follow-up persisted on anti-IL17, with the highest rate observed in the IXE cohort, followed by the SECU150 then SECU300 cohorts.

Abacavir Increases Purinergic P2X7 Receptor Activation by ATP: Does a Pro-inflammatory Synergism Underlie Its Cardiovascular Toxicity?

The cardiovascular toxicity of Abacavir is related to its purinergic structure. Purinergic P2X7-receptors (P2X7R), characterized by activation by high concentrations of ATP and with high plasticity, seem implicated. We appraise the nature of the interplay between Abacavir and P2X7R in generating vascular inflammation. The effects of Abacavir on leukocyte-endothelium interactions were compared with those of its metabolite carbovir triphosphate (CBV-TP) or ATP in the presence of apyrase (ATP-ase) or A804598 (P2X7R-antagonist). CBV-TP and ATP levels were evaluated by HPLC, while binding of Abacavir, CBV-TP and ATP to P2X7R was assessed by radioligand and docking studies. Hypersensitivity studies explored a potential allosteric action of Abacavir. Clinical concentrations of Abacavir (20 µmol/L) induced leukocyte-endothelial cell interactions by specifically activating P2X7R, but the drug did not show affinity for the P2X7R ATP-binding site (site 1). CBV-TP levels were undetectable in Abacavir-treated cells, while those of ATP were unaltered. The effects of Abacavir were Apyrase-dependent, implying dependence on endogenous ATP. Exogenous ATP induced a profile of proinflammatory actions similar to Abacavir, but was not entirely P2X7R-dependent. Docking calculations suggested ATP-binding to sites 1 and 2, and Abacavir-binding only to allosteric site 2. A combination of concentrations of Abacavir (1 µmol/L) and ATP (0.1 µmol/L) that had no effect when administered separately induced leukocyte-endothelium interactions mediated by P2X7R and involving Connexin43 channels. Therefore, Abacavir acts as a positive allosteric modulator of P2X7R, turning low concentrations of endogenous ATP themselves incapable of stimulating P2X7R into a functional proinflammatory agonist of the receptor.

New Therapeutic Strategies for Osteoarthritis by Targeting Sialic Acid Receptors.

Osteoarthritis (OA) is the most common degenerative joint disease characterized by articular cartilage degradation and joint degeneration. The articular cartilage is mainly formed by chondrocytes and a collagen-proteoglycan extracellular matrix that contains high levels of glycosylated proteins. It was reported that the shift from glycoproteins containing α-2,6-linked sialic acids to those that contain α-2,3 was associated with the onset of common types of arthritis. However, the pathophysiology of α-2,3-sialylation in cartilage has not been yet elucidated. We show that cartilage from osteoarthritic patients expresses high levels of the α-2,3-sialylated transmembrane mucin receptor, known as podoplanin (PDPN). Additionally, the Maackia amurensis seed lectin (MASL), that can be utilized to target PDPN, attenuates the inflammatory response mediated by NF-kB activation in primary chondrocytes and protects human cartilage breakdown ex vivo and in an animal model of arthritis. These findings reveal that specific lectins targeting α-2,3-sialylated receptors on chondrocytes might effectively inhibit cartilage breakdown. We also present a computational 3D molecular model for this interaction. These findings provide mechanistic information on how a specific lectin could be used as a novel therapy to treat degenerative joint diseases such as osteoarthritis.

Precursors for cytochrome P450 profiling breath tests from an in silico screening approach.

The family of cytochrome P450 enzymes (CYPs) is a major player in the metabolism of drugs and xenobiotics. Genetic polymorphisms and transcriptional regulation give a complex patient-individual CYP activity profile for each human being. Therefore, personalized medicine demands easy and non-invasive measurement of the CYP phenotype. Breath tests detect volatile organic compounds (VOCs) in the patients' exhaled air after administration of a precursor molecule. CYP breath tests established for individual CYP isoforms are based on the detection of (13)CO2 or (14)CO2 originating from CYP-catalyzed oxidative degradation reactions of isotopically labeled precursors.We present an in silico work-flow aiming at the identification of novel precursor molecules, likely to result in VOCs other than CO2 upon oxidative degradation as we aim at label-free precursor molecules. The ligand-based work-flow comprises five parts: (1) CYP profiling was encoded as a decision tree based on 2D molecular descriptors derived from established models in the literature and validated against publicly available data extracted from the DrugBank. (2) Likely sites of metabolism were identified by reactivity and accessibility estimation for abstractable hydrogen radical. (3) Oxidative degradation reactions (O- and N-dealkylations) were found to be most promising in the release of VOCs. Thus, the CYP-catalyzed oxidative degradation reaction was encoded as SMIRKS (a programming language style to implement reactions based on the SMARTS description) to enumerate possible reaction products. (4) A quantitative structure property relation (QSPR) model aiming to predict the Henry constant H was derived from data for 488 organic compounds and identifies potentially VOCs amongst CYP reaction products. (5) A blacklist of naturally occurring breath components was implemented to identify marker molecules allowing straightforward detection within the exhaled air.Evident oxidative degradation reactions served as test case for the screening approach. Comparisons to metabolism data from literature support the results' plausibility. Thus, a large scale screening for potential novel breath test precursor using the presented five stage work-flow is promising.