40 years of glyco-polyacrylamide in glycobiology

Automated glycan-bead coupling for high throughput, highly reproducible anti-glycan antibody analysis

Automation of diagnostic assays generally aims to increase reproducibility and throughput while decreasing human errors and hands-on time. Here, we introduce a protocol for the automated chemical conjugation of glycans to color-coded magnetic beads using the KingFisher Flex magnetic particle processor. The resulting glycan-coupled magnetic beads allow the detection of anti-glycan antibodies of different isotypes from various species. By generating anti-glycan antibody profiles, monoclonal antibodies can be screened for their specificity and cross-reactivity, while anti-glycan antibody profiles from different human body fluids can aid in predicting response to treatment or outcome of disease. This efficient, scalable protocol can also be adapted to attach proteins and other biomolecules to beads, making it useful for a wider range of applications that require bead-based laboratory methods.

Synthetic pentatrideca-valent triazolylsialoside inhibits influenza virus hemagglutinin/neuraminidase and aggregates virion particles

A synthetic multivalent hemagglutinin and neuraminidase inhibitor was developed by the conjugation of a septa-valent triazolylsialoside to bovine serum albumin using di-(N-succinimidyl) adipate. Matrixassisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) confirmed the attachment of five septa-valent sialyl lactosides to the protein backbone, resulting in a pentatrideca-valent sialyl conjugate. This pseudo-glycoprotein demonstrated a high affinity for hemagglutinin/neuraminidase as well as for the drug-resistant NA mutation on the influenza virus surface due to the cluster effect. The conjugate also exhibited potent antiviral activity against a wide range of virus strains without cytotoxicity at high concentrations. Mechanistic studies revealed that the pentatrideca-valent sialyl conjugate bound strongly to the influenza virion particles through interactions with HA/NA on the virion surfaces. The KD of the interaction was approximately 1 μM, as determined by isothermal calorimetric titration, allowing the capture and trapping of the influenza virions and preventing their further infection of host cells. These findings provide insight into the development of new antiviral agents using multivalent sialic acid clusters.

Highly Selective Adsorption of 99TcO4-/ReO4- by a Novel Polyamide-Functionalized Polyacrylamide Polymer Material

The treatment of radioactive wastewater is one of the major problems in the current research. With the development of nuclear energy, the efficient removal of ⁹⁹TcO₄^- in radioactive wastewater has attracted the attention of countries all over the world. In this study, a novel functional polyamide polymer p-(Amide)-PAM was synthesized by the two-step method. The experimental results show that p-(Amide)-PAM has good adsorptive properties for ⁹⁹TcO₄^-/ReO₄^- and has good selectivity in the nitric acid system. The kinetics of the reaction of p-(Amide)-PAM with ⁹⁹TcO₄^-/ReO₄^- was studied. The results show that p-(Amide)-PAM has a fast adsorption rate for ⁹⁹TcO₄^-/ReO₄^-, the saturated adsorption capacity reaches 346.02 mg/g, and the material has good reusability. This new polyamide-functionalized polyacrylamide polymer material has good application prospects in the removal of ⁹⁹TcO₄^- from radioactive wastewater.

Prospects and Challenges of the Study of Anti-Glycan Antibodies and Microbiota for the Monitoring of Gastrointestinal Cancer

Over the past decades, a large amount of data has been accumulated in various subfields of glycobiology. However, much clinically relevant data and many tools are still not widely used in medicine. Synthetic glycoconjugates with the known structure of glycans are an accurate tool for the study of glycan-binding proteins. We used polyacrylamide glycoconjugates (PGs) including PGs with tumour-associated glycans (TAGs) in immunoassays to assess the prognostic potential of the serum level of anti-glycan antibodies (AG Abs) in gastrointestinal cancer patients and found an association of AG Abs with survival. The specificity of affinity-isolated AG Abs was investigated using synthetic and natural glycoconjugates. AG Abs showed mainly a low specificity to tumour-associated and tumour-derived mucins; therefore, the protective role of the examined circulating AG Abs against cancer remains a challenge. In this review, our findings are analysed and discussed in the context of the contribution of bacteria to the AG Abs stimulus and cancer progression. Examples of the influence of pathogenic bacteria colonising tumours on cancer progression and patient survival through mechanisms of interaction with tumours and dysregulated immune response are considered. The possibilities and problems of the integrative study of AG Abs and the microbiome using high-performance technologies are discussed.

Characterization of changes in the hemagglutinin that accompanied the emergence of H3N2/1968 pandemic influenza viruses

The hemagglutinin (HA) of A/H3N2 pandemic influenza viruses (IAVs) of 1968 differed from its inferred avian precursor by eight amino acid substitutions. To determine their phenotypic effects, we studied recombinant variants of A/Hong Kong/1/1968 virus containing either human-type or avian-type amino acids in the corresponding positions of HA. The precursor HA displayed receptor binding profile and high conformational stability typical for duck IAVs. Substitutions Q226L and G228S, in addition to their known effects on receptor specificity and replication, marginally decreased HA stability. Substitutions R62I, D63N, D81N and N193S reduced HA binding avidity. Substitutions R62I, D81N and A144G promoted viral replication in human airway epithelial cultures. Analysis of HA sequences revealed that substitutions D63N and D81N accompanied by the addition of N-glycans represent common markers of avian H3 HA adaptation to mammals. Our results advance understanding of genotypic and phenotypic changes in IAV HA required for avian-to-human adaptation and pandemic emergence.

SARS-CoV-2 Peptide Bioconjugates Designed for Antibody Diagnostics

In the near future, the increase in the number of required tests for COVID-19 antibodies is expected to be many hundreds of millions. Obviously, this will be done using a variety of analytical methods and using different antigens, including peptides. In this work, we compare three method variations for detecting specific immunoglobulins directed against peptides of approximately 15-aa of the SARS-CoV-2 spike protein. These linear peptide epitopes were selected using antigenicity algorithms, and were synthesized with an additional terminal cysteine residue for their bioconjugation. In two of the methods, constructs were prepared where the peptide (F, function) is attached to a negatively charged hydrophilic spacer (S) linked to a dioleoylphosphatidyl ethanolamine residue (L, lipid) to create a function-spacer-lipid construct (FSL). These FSLs were easily and controllably incorporated into erythrocytes for serologic testing or in a lipid bilayer deposited on a polystyrene microplate for use in an enzyme immunoassays (EIA). The third method, also an EIA, used polyacrylamide conjugated peptides (peptide-PAA) prepared by controlled condensation of the cysteine residue of the peptide with the maleimide-derived PAA polymer which were immobilized on polystyrene microplates by physisorption of the polymer. In this work, we describe the synthesis of the PAA and FSL peptide bioconjugates, design of test systems, and comparison of the bioassays results, and discuss potential reasons for higher performance of the FSL conjugates, particularly in the erythrocyte-based serologic assay.

Missing the sweet spot: one of the two N-glycans on human Gb3/CD77 synthase is expendable

N-glycosylation is a ubiquitous posttranslational modification that may influence folding, subcellular localization, secretion, solubility and oligomerization of proteins. In this study, we examined the effects of N-glycans on the activity of human Gb3/CD77 synthase, which catalyzes the synthesis of glycosphingolipids with terminal Galα1 → 4Gal (Gb3 and the P1 antigen) and Galα1 → 4GalNAc disaccharides (the NOR antigen). The human Gb3/CD77 synthase contains two occupied N-glycosylation sites at positions N121 and N203. Intriguingly, we found that while the N-glycan at N203 is essential for activity and correct subcellular localization, the N-glycan at N121 is dispensable and its absence did not reduce, but, surprisingly, even increased the activity of the enzyme. The fully N-glycosylated human Gb3/CD77 synthase and its glycoform missing the N121 glycan correctly localized in the Golgi, whereas a glycoform without the N203 site partially mislocalized in the endoplasmic reticulum. A double mutein missing both N-glycans was inactive and accumulated in the endoplasmic reticulum. Our results suggest that the decreased specific activity of human Gb3/CD77 synthase glycovariants results from their improper subcellular localization and, to a smaller degree, a decrease in enzyme solubility. Taken together, our findings show that the two N-glycans of human Gb3/CD77 synthase have opposing effects on its properties, revealing a dual nature of N-glycosylation and potentially a novel regulatory mechanism controlling the biological activity of proteins.

COVID-19 antibody screening with SARS-CoV-2 red cell kodecytes using routine serologic diagnostic platforms

Background

The Coronavirus disease 2019 (COVID‐19) pandemic is having a major global impact, and the resultant response in the development of new diagnostics is unprecedented. The detection of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has a role in managing the pandemic. We evaluated the feasibility of using SARS‐CoV‐2 peptide Kode Technology‐modified red cells (C19‐kodecytes) to develop an assay compatible with existing routine serologic platforms.

Study Design and Methods

A panel of eight unique red cells modified using Kode Technology function‐spacer‐lipid constructs and bearing short SARS‐CoV‐2 peptides was developed (C19‐kodecyte assay). Kodecytes were tested against undiluted expected antibody‐negative and ‐positive plasma samples in manual tube and three column agglutination technology (CAT) platforms. Parallel analysis with the same peptides in solid phase by enzyme immunoassays was performed. Evaluation samples included >120 expected negative blood donor samples and >140 COVID‐19 convalescent plasma samples, with independent serologic analysis from two centers.

Results

Specificity (negative reaction rate against expected negative samples) in three different CAT platforms against novel C19‐kodecytes was >91%, which correlated with published literature. Sensitivity (positive reaction rate against expected positive convalescent, PCR‐confirmed samples) ranged from 82% to 97% compared to 77% with the Abbott Architect SARS‐CoV‐2 IgG assay. Manual tube serology was less sensitive than CAT. Enzyme immunoassay results with some Kode Technology constructs also had high sensitivity.

Conclusions

C19‐kodecytes are viable for use as serologic reagent red cells for the detection of SARS‐CoV‐2 antibody with routine blood antibody screening equipment.