ABH-blood-group antigens and glycolipids of human saliva

Carbohydrate Ligands for COVID-19 Spike Proteins

An outbreak of SARS-CoV-2 coronavirus (COVID-19) first detected in Wuhan, China, has created a public health emergency all over the world. The pandemic has caused more than 340 million confirmed cases and 5.57 million deaths as of 23 January 2022. Although carbohydrates have been found to play a role in coronavirus binding and infection, the role of cell surface glycans in SARS-CoV-2 infection and pathogenesis is still not understood. Herein, we report that the SARS-CoV-2 spike protein S1 subunit binds specifically to blood group A and B antigens, and that the spike protein S2 subunit has a binding preference for Le^a antigens. Further examination of the binding preference for different types of red blood cells (RBCs) indicated that the spike protein S1 subunit preferentially binds with blood group A RBCs, whereas the spike protein S2 subunit prefers to interact with blood group Le^a RBCs. Angiotensin converting enzyme 2 (ACE2), a known target of SARS-CoV-2 spike proteins, was identified to be a blood group A antigen-containing glycoprotein. Additionally, 6-sulfo N-acetyllactosamine was found to inhibit the binding of the spike protein S1 subunit with blood group A RBCs and reduce the interaction between the spike protein S1 subunit and ACE2.

OUP accepted manuscript

Host carbohydrates, or glycans, have been implicated in the pathogenesis of many bacterial infections. Group A Streptococcus (GAS) is a Gram-positive bacterium that readily colonises the skin and oropharynx, and is a significant cause of mortality in humans. While the glycointeractions orchestrated by many other pathogens are increasingly well-described, the understanding of the role of human glycans in GAS disease remains incomplete. Although basic investigation into the mechanisms of GAS disease is ongoing, several glycointeractions have been identified and are examined herein. The majority of research in this context has focussed on bacterial adherence, however, glycointeractions have also been implicated in carbohydrate metabolism; evasion of host immunity; biofilm adaptations; and toxin-mediated haemolysis. The involvement of human glycans in these diverse avenues of pathogenesis highlights the clinical value of understanding glycointeractions in combatting GAS disease.

Discovery of Pancreatic Ductal Adenocarcinoma-Related Aberrant Glycosylations: A Multilateral Approach of Lectin Microarray-Based Tissue Glycomic Profiling With Public Transcriptomic Datasets

Aberrant protein glycosylation is one of the most notable features in cancerous tissues, and thereby glycoproteins with disease-relevant glycosylation alterations are fascinating targets for the development of biomarkers and therapeutic agents. For this purpose, a reliable strategy is needed for the analysis of glycosylation alterations occurring on specific glycoproteins during the progression of cancer. Here, we propose a bilateral approach combining lectin microarray-based tissue glycomic profiling and database-derived transcriptomic datasets. First, lectin microarray was used to perform differential glycomic profiling of crude extracts derived from non-tumor and tumor regions of frozen tissue sections from pancreatic ductal adenocarcinoma (PDAC). This analysis revealed two notable tissue glycome alterations in PDAC samples: increases in sialylated glycans and bisecting N-acetylglucosamine and a decrease in ABO blood group antigens. To examine aberrations in the glycosylation machinery related to these glycomic alterations, we next employed public datasets of gene expression profiles in cancerous and normal pancreases provided by The Cancer Genome Atlas and the Genotype-Tissue Expression projects, respectively. In this analysis, glycosyltransferases responsible for the glycosylation alterations showed aberrant gene expression in the cancerous tissues, consistent with the tissue glycomic profiles. The correlated alterations in glycosyltransferase expression and tissue glycomics were then evaluated by differential glycan profiling of a membrane N-glycoprotein, basigin, expressed in tumor and non-tumor pancreatic cells. The focused differential glycomic profiling for endogenous basigin derived from non-tumor and cancerous regions of PDAC tissue sections demonstrated that PDAC-relevant glycan alterations of basigin closely reflected the notable features in the disease-specific alterations in the tissue glycomes. In conclusion, the present multi-omics strategy using public transcriptomic datasets and experimental glycomic profiling using a tiny amount of clinical specimens successfully demonstrated that basigin is a representative N-glycoprotein that reflects PDAC-related aberrant glycosylations. This study indicates the usefulness of large public data sets such as the gene expression profiles of glycosylation-related genes for evaluation of the highly sensitive tissue glycomic profiling results. This strategy is expected to be useful for the discovery of novel glyco-biomarkers and glyco-therapeutic targets.

Blood Group Antigen Recognition via the Group A Streptococcal M Protein Mediates Host Colonization

Streptococcus pyogenes (group A streptococcus [GAS]) is responsible for over 500,000 deaths worldwide each year. The highly virulent M1T1 GAS clone is one of the most frequently isolated serotypes from streptococcal pharyngitis and invasive disease. The oral epithelial tract is a niche highly abundant in glycosylated structures, particularly those of the ABO(H) blood group antigen family. Using a high-throughput approach, we determined that a strain representative of the globally disseminated M1T1 GAS clone 5448 interacts with numerous, structurally diverse glycans. Preeminent among GAS virulence factors is the surface-expressed M protein. M1 protein showed high affinity for several terminal galactose blood group antigen structures. Deletion mutagenesis shows that M1 protein mediates glycan binding via its B repeat domains. Association of M1T1 GAS with oral epithelial cells varied significantly as a result of phenotypic differences in blood group antigen expression, with significantly higher adherence to those cells expressing H antigen structures compared to cells expressing A, B, or AB antigen structures. These data suggest a novel mechanism for GAS attachment to host cells and propose a link between host blood group antigen expression and M1T1 GAS colonization.

IMPORTANCE

There has been a resurgence in group A streptococcal (GAS) invasive disease, which has been paralleled by the emergence of the highly virulent M1T1 GAS clone. Intensive research has focused on mechanisms that contribute to the invasive nature of this serotype, while the mechanisms that contribute to host susceptibility to disease and bacterial colonization and persistence are still poorly understood. The M1T1 GAS clone is frequently isolated from the throat, an environment highly abundant in blood group antigen structures. This work examined the interaction of the M1 protein, the preeminent GAS surface protein, against a wide range of host-expressed glycan structures. Our data suggest that susceptibility to infection by GAS in the oral tract may correlate with phenotypic differences in host blood group antigen expression. Thus, variations in host blood group antigen expression may serve as a selective pressure contributing to the dissemination and overrepresentation of M1T1 GAS.

Blood group antigen loci demonstrate multivariate genetic associations with circulating cellular adhesion protein levels in the Multi-Ethnic Study of Atherosclerosis

The cellular adhesion pathway is critical in the pathophysiology of atherosclerosis, and genetic factors contributing to regulation of circulating levels of related proteins may be relevant to risk prediction of cardiovascular disease. In contrast to conducting separate genome-wide protein quantitative trait loci (pQTL) mapping analyses of each individual protein, joint genetic association analyses of multiple quantitative traits can leverage cross-trait co-variation and identify simultaneous regulatory effects on protein levels across the pathway. We conducted a multi-pQTL (mpQTL) analysis of 15 proteins related to cellular adhesion assayed on 2313 participants from the Multi-Ethnic Study of Atherosclerosis (MESA). We applied the MQFAM multivariate association analysis method in PLINK on normalized protein level residuals derived from univariate linear regression, adjusting for age, sex, and principal components of ancestry. Race/ethnicity-stratified analyses identified nine genome-wide significant (P < 5e-08) loci associated with co-variation of protein levels. Although the majority of these SNPs were in proximity to structural genes of the assayed proteins, we discovered multiple loci demonstrating co-association with the circulation of at least two proteins. Of these, two significant loci specific to non-Hispanic white participants, rs17074898 at ALOX5AP (P = 1.78E-08) and rs7521237 at KIAA1614 (P = 2.2E-08), would not have met statistical significance using univariate analyses. Moreover, common patterns of multi-protein associations were discovered at the ABO locus across race/ethnicity. These results indicate the biological relevance of blood group antigens on regulation of circulating cellular adhesion pathway proteins while also demonstrating race/ethnicity-specific co-regulatory effects.

Higher frequency of secretor phenotype in O blood group - its benefits in prevention and/or treatment of some diseases

ABO blood groups and secretor status are important in clinical and forensic medicine and in relation to some diseases. There are geographic and racial differences in their frequencies, but the frequency of secretor status in different ABO blood group systems has not been determined yet. Therefore, the aim of this study was mainly to determine this point. Blood and saliva from 762 randomly selected apparently healthy adult individuals (480 men and 282 women) were examined to determine their ABO and Rhesus blood groups by standard conventional methods, and their secretor status by using Lewis blood grouping and/or hemagglutination inhibition test of saliva. Results showed that 76.1% of the study population were ABH blood group antigens secretors and 23.9% were nonsecretors. The frequencies of secretor status in different ABO blood groups were 70.1% in group A, 67.8% in group B, 67.9% in group AB, and 88.3% in group O. In conclusion, blood group O individuals have significantly higher frequency of secretor status than non-O blood group individuals. This finding would be beneficial to them, protecting them, at least partially, from certain malignancies or allowing them to have less aggressive disease, and this finding might be useful in enhancing further studies and research in this direction.

Identification and isolation of Lewis blood group antigens from human saliva using monoclonal antibodies

Solid-phase radioimmunoassay, polyacrylamide gel electrophoresis and thin-layer chromatography were used to compare, identify, and characterize the Lewis antigens from human salivas, using monoclonal antibodies directed to the Lea and Leb determinants. Sialylated Lea glycolipid was detected in saliva from individuals with Le(a+ b+) and Le(a+ b-) phenotypes. Immunoaffinity chromatography of the saliva from individuals with different phenotypes revealed a glycoprotein of molecular weight greater than 200 kD bearing the Lewis antigenic determinants.

Determination of salivary ABH-blood group antigens by rocket affinoelectrophoresis

A rocket affinoelectrophoretic assay system was used to detect and quantify the human salivary ABH-blood group antigens of 155 individuals. In this system blood group antigens precipitated as rockets in agarose gels containing different lectins, with the rocket height being correlated to the antigen concentration. This technique was compared with the classical hemagglutination inhibition method for determination of salivary blood group antigens, and it was demonstrated that salivary A, B and H blood group antigens were detected with the lectins from helix pomatia, Bandeiraea simplicifolia and Ulex europeus, respectively. The technique was rapid and sensitive, with a detection limit of 0.1 microliters saliva. This technique can also be used for determination of blood group antigens derived from other body fluids, tissues and cells.

A new method for the isolation of the simple and highly complex glycosphingolipids from animal tissue

The most widely used methods for the extraction of glycosphingolipids from animal tissues are based on the use of chloroform/methanol mixtures. These methods, although suitable for a great majority of lipids, fail to remove highly complex glycosphingolipids. Reported here is a method for the isolation of the entire population of glycosphingolipids by means of a gradual degradation of tissue components and enrichment in carbohydrate conjugates resistant to alkali and proteases. Fresh gastric mucosa was homogenized and treated with alkali (beta-elimination) and RNAase and DNAase to decrease the viscosity of the homogenate, followed by pronase digestion. Each treatment was completed by exhaustive dialysis against distilled water. The resultant tissue digest was partitioned with chloroform/methanol (2:1) to remove simple glycosphingolipids. The aqueous portion of the system was adjusted to 1.0% with Zwittergent TM- 314 and solubilized for 24 h by mixing. Thus, prepared sample subjected to Bio-Gel P60 column chromatography afforded five fractions. Of these, three were free of protein and contained carbohydrates, fatty acids and sphingosine. Further fractionation on Bio-Gel P 10 and P6 columns followed by thin-layer chromatography afforded homogeneous components with all the characteristics of highly complex glycosphingolipids.