Glyco-epitope Diversity: An Evolving Area of Glycomics Research and Biomarker Discovery

Insights Into Glycobiology and the Protein-Glycan Interactome Using Glycan Microarray Technologies

Glycans linked to proteins and lipids and also occurring in free forms have many functions, and these are partly elicited through specific interactions with glycan-binding proteins (GBPs). These include lectins, adhesins, toxins, hemagglutinins, growth factors, and enzymes, but antibodies can also bind glycans. While humans and other animals generate a vast repertoire of GBPs and different glycans in their glycomes, other organisms, including phage, microbes, protozoans, fungi, and plants also express glycans and GBPs, and these can also interact with their host glycans. This can be termed the protein-glycan interactome, and in nature is likely to be vast, but is so far very poorly described. Understanding the breadth of the protein-glycan interactome is also a key to unlocking our understanding of infectious diseases involving glycans, and immunology associated with antibodies binding to glycans. A key technological advance in this area has been the development of glycan microarrays. This is a display technology in which minute quantities of glycans are attached to the surfaces of slides or beads. This allows the arrayed glycans to be interrogated by GBPs and antibodies in a relatively high throughput approach, in which a protein may bind to one or more distinct glycans. Such binding can lead to novel insights and hypotheses regarding both the function of the GBP, the specificity of an antibody and the function of the glycan within the context of the protein-glycan interactome. This article focuses on the types of glycan microarray technologies currently available to study animal glycobiology and examples of breakthroughs aided by these technologies.

Targeting the stage-specific embryonic antigen (SSEA)-0 tumor neoantigen

Recognition of abnormal glycosylation in virtually any cancer type has raised a great interest in the glycan-based tumor biomarkers. Our team explored carbohydrate microarrays as a broad-spectrum immunoassay to probe the immunologically potent tumor glycan targets. This effort has led to the identification of a blood group precursor antigen SSEA-0 as a conserved breast cancer (BCA) marker. Since this immunogenic O-core glycan is normally hidden as a cryptic antigen but becomes overexpressed and surface-exposed by metastatic breast cancer cells (MBCA), its potential as a novel immunological target for precision immunotherapy against tumor metastasis warrants a focused investigation.

Influence of N-glycosylation in the A and C domains on the immunogenicity of factor VIII

The most significant complication in hemophilia A treatment is the formation of inhibitors against factor VIII (FVIII) protein. Glycans and glycan-binding proteins are central to a properly functioning immune system. This study focuses on whether glycosylation of FVIII plays an important role in induction and regulation of anti-FVIII immune responses. We investigated the potential roles of 4 N-glycosylation sites, including N41 and N239 in the A1 domain, N1810 in the A3 domain, and N2118 in the C1 domain of FVIII, in moderating its immunogenicity. Glycomics analysis of plasma-derived FVIII revealed that sites N41, N239, and N1810 contain mostly sialylated complex glycoforms, while high mannose glycans dominate at site N2118. A missense variant that substitutes asparagine (N) to glutamine (Q) was introduced to eliminate glycosylation on each of these sites. Following gene transfer of plasmids encoding B domain deleted FVIII (BDD-FVIII) and each of these 4 FVIII variants, it was found that specific activity of FVIII in plasma remained similar among all treatment groups. Slightly increased or comparable immune responses in N41Q, N239Q, and N1810Q FVIII variant plasmid-treated mice and significantly decreased immune responses in N2118Q FVIII plasmid-treated mice were observed when compared with BDD-FVIII plasmid-treated mice. The reduction of inhibitor response by N2118Q FVIII variant was also demonstrated in AAV-mediated gene transfer experiments. Furthermore, a specific glycopeptide epitope surrounding the N2118 glycosylation site was identified and characterized to activate T cells in an FVIII-specific proliferation assay. These results indicate that N-glycosylation of FVIII can have significant impact on its immunogenicity.

Polysaccharides for tissue engineering: Current landscape and future prospects

Biological studies on the importance of carbohydrate moieties in tissue engineering have incited a growing interest in the application of polysaccharides as scaffolds over the past two decades. This review provides a perspective of the recent approaches in developing polysaccharide scaffolds, with a focus on their chemical modification, structural versatility, and biological applicability. The current major limitations are assessed, including structural reproducibility, the narrow scope of polysaccharide modifications being applied, and the effective replication of the extracellular environment. Areas with opportunities for further development are addressed with an emphasis on the application of rationally designed polysaccharides and their importance in elucidating the molecular interactions necessary to properly design tissue engineering materials.