polysaccharideprotein

Polysaccharide–protein conjugates are macromolecules in which carbohydrate chains are bound to a protein, by covalent or non-covalent links. They occur naturally as glycoproteins, in which oligosaccharides are attached to protein backbones, and as proteoglycans, where long glycosaminoglycan chains are covalently linked to a core protein. Artificial polysaccharide–protein conjugates are also prepared to modify immunogenicity, stability, or other functional properties in research, medicine, and industry.

Natural glycoproteins and proteoglycans play essential roles in biology. Glycoproteins are involved in cell signaling, adhesion, immune recognition, and circulating transport, while proteoglycans contribute to the structural and hydration properties of the extracellular matrix and influence cell behavior. In the context of vaccines, chemically or enzymatically prepared polysaccharide–protein conjugates allow often poorly immunogenic polysaccharide antigens to engage T-cell help, enhancing the overall immune response.

In vaccines, polysaccharide antigens from bacteria such as Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis are conjugated to protein carriers (for example CRM197, tetanus toxoid, or diphtheria toxoid). This conversion from a T-independent to a T-dependent response improves immunogenicity in infants and yields longer-lasting protection. Beyond vaccines, polysaccharide–protein interactions influence the texture and stability of food products and the properties of biopolymer materials, while in biology they underpin communication and adhesion at cell surfaces.

Characterization and production of these conjugates face challenges due to heterogeneity in linkage and composition, prompting ongoing methodological advances in analytic and synthetic techniques.