Contreras M, Vaz-Rodrigues R, Mazuecos L, Villar M, Artigas-Jerónimo S, et al.
Parasites & vectors •
Alpha-Gal syndrome (AGS) is a tick-borne food allergy caused by IgE antibodies against the glycan galactose-alpha-1,3-galactose (α-Gal) present in glycoproteins and glycolipids from mammalian meat. To advance in the diagnosis and treatment of AGS, further research is needed to unravel the molecular and immune mechanisms underlying this syndrome. The objective of this study is the characterization of tick salivary components and proteins with and without α-Gal modifications involved in modulating human immune response against this carbohydrate. Protein and α-Gal content were determined in tick saliva components, and proteins were identified by proteomics analysis of tick saliva fractions. Pathophysiological changes were recorded in the zebrafish (Danio rerio) model after exposure to distinct Ixodes ricinus tick salivary components. Serum samples were collected from zebrafish at day 8 of exposure to determine anti-α-Gal, anti-glycan, and anti-tick saliva protein IgM antibody titers by enzyme-linked immunosorbent assay (ELISA). Zebrafish treated with tick saliva and saliva protein fractions combined with non-protein fractions demonstrated significantly higher incidence of hemorrhagic type allergic reactions, abnormal behavioral patterns, or mortality when compared to the phosphate-buffered saline (PBS)-treated control group. The main tick salivary proteins identified in these fractions with possible functional implication in AGS were the secreted protein B7P208-salivary antigen p23 and metalloproteases. Anti-α-Gal and anti-tick salivary gland IgM antibody titers were significantly higher in distinct saliva protein fractions and deglycosylated saliva group when compared with PBS-treated controls. Anti-glycan antibodies showed group-related profiles. Results support the hypothesis that tick salivary biomolecules with and without α-Gal modifications are involved in modulating immune response against this carbohydrate.
A structurally diverse capsular polysaccharide (CPS) in the outer cell envelope plays an important role in the virulence of the important bacterial pathogen, Acinetobacter baumannii. More than 75 different CPS structures have been determined for the species to date, and many CPSs include isomers of a higher sugar, namely 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acid. Recently, a novel isomer having the d-glycero-l-manno configuration (5,7-di-N-acetyl-8-epipseudaminic acid; 8ePse5Ac7Ac) has been identified in the CPS from A. baumannii clinical isolate RES-546 [Carbohydr. Res. 513 (2022) 108,531]. Here, the complete chemical structure of this CPS, designated K135, was elucidated. The CPS was found to have a branched tetrasaccharide K unit and to include the higher sugar as part of a 8ePse5Ac7Ac-(2 → 6)-α-Gal disaccharide branching from a →3)-α-D-GlcpNAc-(1 → 3)-β-D-GlcpNAc-(1→ main chain. Assignment of glycosyltransferases encoded by the CPS biosynthesis gene cluster in the RES-546 genome enabled the first sugar of the K unit, and hence the topology of the K135 CPS, to be determined.
Mizgina TO, Chikalovets IV, Bulanova TA, Molchanova VI, Filshtein AP, et al.
Marine drugs •
In this study, a new l-rhamnose-binding lectin (GYL-R) from the hemolymph of bivalve was purified using affinity and ion-exchange chromatography and functionally characterized. Lectin antimicrobial activity was examined in different ways. The lectin was inhibited by saccharides possessing the same configuration of hydroxyl groups at C-2 and C-4, such as l-rhamnose, d-galactose, lactose, l-arabinose and raffinose. Using the glycan microarray approach, natural carbohydrate ligands were established for GYL-R as l-Rha and glycans containing the α-Gal residue in the terminal position. The GYL-R molecular mass determined by MALDI-TOF mass spectrometry was 30,415 Da. The hemagglutination activity of the lectin was not affected by metal ions. The lectin was stable up to 75 °C and between pH 4.0 and 12.0. The amino acid sequence of the five GYL-R segments was obtained with nano-ESI MS/MS and contained both YGR and DPC-peptide motifs which are conserved in most of the l-rhamnose-binding lectin carbohydrate recognition domains. Circular dichroism confirmed that GYL is a α/β-protein with a predominance of the random coil. Furthermore, GYL-R was able to bind and suppress the growth of the Gram-negative bacteria by recognizing lipopolysaccharides. Together, these results suggest that GYL-R is a new member of the RBL family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity.
Complement has significant status in the field of transfusion medicine. The accepted stability profile of complement is based on historical studies of diluted human serum hemolyzing rabbit heterophile antibody-sensitized sheep red blood cells (RBCs). Contemporary tools are available to reevaluate these historical observations using human heterophile antibodies, undiluted serum, and antigen-modified human RBCs. Human RBCs were made into "animal-like" kodecytes with heterophile Galα3Galβ4GlcNAcβ function-spacer-lipid constructs. These α-Gal-kodecytes were prepared with an antigen dilution capable of consistently producing 50% antibody-mediated hemolysis against human α1-3galactose heterophile antibodies and undiluted standardized serum. Standardized human serum aliquots from a two-donor pool stored at -85, -20, 4, 22, and 37°C for durations of up to 150 days were evaluated for loss of hemolytic activity. Where practical methodologic procedures were aligned with historical studies. Comparison of the historical assay with the α-Gal-kodecyte assay against complement activity standards showed concordance. However, in most scenarios complement was found to be more than twice as stable as generally accepted. At least 60% of complement hemolytic activity was observed in serum stored at 22°C for 1 week or 2 months at 4°C. No loss of hemolytic activity was observed after 5 months' storage at temperatures below -20°C. An alternative method using undiluted serum and modified human RBCs observed that classical-pathway complement hemolytic activity in stored human serum is at least twice as stable as previously accepted.
Influenza A viruses of domestic birds originate from the natural reservoir in aquatic birds as a result of interspecies transmission and adaptation to new host species. We previously noticed that influenza viruses isolated from distinct orders of aquatic and terrestrial birds may differ in their fine receptor-binding specificity by recognizing the structure of the inner parts of Neu5Ac alpha 2-3Gal-terminated sialyloligosaccharide receptors. To further characterize these differences, we studied receptor-binding properties of a large panel of influenza A viruses from wild aquatic birds, poultry, pigs and horses. Using a competitive solid-phase binding assay, we determined viral binding to polymeric conjugates of sialyloligosaccharides differing by the type of Neu5Ac alpha-Gal linkage and by the structure of the more distant parts of the oligosaccharide chain. Influenza viruses isolated from terrestrial poultry differed from duck viruses by an enhanced binding to sulfated and/or fucosylated Neu5Ac alpha 2-3Gal-containing sialyloligosaccharides. Most of the poultry viruses tested shared a high binding affinity for the 6-sulfo sialyl Lewis X (Su-SLex). Efficient binding of poultry viruses to Su-SLex was often accompanied by their ability to bind to Neu5Ac alpha 2-6Gal-terminated (human-type) receptors. Such a dual receptor-binding specificity was demonstrated for the North American and Eurasian H7 viruses, H9N2 Eurasian poultry viruses, and H1, H3 and H9 avian-like virus isolates from pigs. Influenza viruses of terrestrial poultry differ from ancestral duck viruses by enhanced binding to sulfated and/or fucosylated Neu5Ac alpha 2-3Gal-terminated receptors and, occasionally, by the ability to bind to Neu5Ac alpha 2-6Gal-terminated (human-type) receptors. These findings suggest that the adaptation to receptors in poultry can enhance the potential of an avian virus for avian-to-human transmission and pandemic spread.
Neethling FA, Joziasse D, Bovin N, Cooper DK, Oriol R
Transplant international : official journal of the European Society for Organ Transplantation •
Synthetic galactosyl oligosaccharides were tested for their ability to inhibit the cytotoxic reaction of human and baboon natural antibodies on PK15 cells in culture. Methyl-alpha-Gal gave weak inhibition, Gal alpha 1-3Gal substantially inhibited the reaction (400muM), and Gal alpha 1-3Gal beta 1-4GLcNAc was ten times more efficient (30 muM). The modification from alpha to beta anomeric configuration of the nonreducing end resulted in a complete loss of activity, while substitutions at the reducing end induced only a partial loss of activity. These observations suggest that natural anti-alphaGal antibodies recognize the epitope from its nonreducing end, but that substitutions at the reducing terminus can modify the antibody-binding capacity. Modified tri- and tetrasaccharides are better inhibitors than the disaccharide but not as good as Gal alpha 1-3Gal beta 1-4GlcNAc. The reducing terminus therefore contributes some energy to the reaction, indicating that certain oligosaccharides will be of more potential clinical use than others.