About this Research Topic
The cell wall of most bacteria are covered with a dense layer of polysaccharides that are displayed in different formats. They protect the bacteria from a wide variety of physical, biological, and chemical stresses and play an important role in the bacterial lifecycle. As a typical outermost component of bacteria, polysaccharides often mediate interactions between bacteria and their immediate environments, and thus are implicated as virulence factors for many bacterial pathogens. Bacterial polysaccharides are typically strain-specific, with a high degree of diversity and complexity in terms of structure, modification, length, and connectivity to other biomolecules. Additionally, the structural disparity between bacterial polysaccharides and mammalian glycans confer host immunogenic response. In fact, a plethora of innate and adaptive immune factors seem to target bacteria through the recognition of cell surface saccharides. These properties distinguish bacterial polysaccharides as ideal targets for vaccines against bacterial infections.
Over the last century, glycan-based vaccines have been extremely successful in preventing bacterial infections. However, there are still challenges in conventional vaccine development and production, as well as elucidation of polysaccharide structures and functions of emerging pathogens. For example, appropriate isolation, structural determination and non-disruptive modification of polysaccharides and their manufacturing intermediates is requisite for vaccine success. While bacterial polysaccharides consist of structural repeat units, chemical fragmentation can cause polysaccharide heterogeneity during processing in vaccine manufacture. This situation demands tight control during vaccine production. Strategies to produce better-defined saccharides and/or more effective antigens for vaccine production are needed. Such strategies can include but are not limited to improved isolation, synthesis and development of novel adjuvants. Additionally, some pathogens are difficult to culture. Production of adequate quantities and purity of polysaccharides from some strains can be difficult necessitating other strategies such as production in alternative bacterial species, engineered bacteria, and a range of synthetic platforms. Further, these vaccines generally target a defined set of polysaccharides produced by the target pathogens including serotype variants. As the complexity of modern polysaccharide and polysaccharide conjugate vaccines increases through the number of saccharides targeted, and the chemistries used to produce conjugates are limited, broad-spectrum vaccines that can reduce complexity are highly desired. In the last two decades, bioengineering and chemical synthesis emerged as novel means to produce glycan-based vaccines. Such methods simplify vaccine production and provide more structurally defined vaccine candidates, but they have their own limitations such as difficulties in the synthesis of long sequences of polysaccharides. Therefore, it is necessary to visit the latest research in the field of bacterial polysaccharide, polysaccharide conjugate and other carbohydrate-based vaccines. Original articles and reviews are needed.
The aim of this Research Topic is to gather recent and novel research in the field of bacterial polysaccharides and glycan-based vaccines. We welcome researchers to contribute Original Research and Review articles. Topics of interest include but are not limited to the following:
• Structural analysis of surface polysaccharides and glycoconjugates of emerging bacterial pathogens.
• Novel methods for bacterial polysaccharide structure determination.
• Genetic and biochemical characterization of biosynthetic pathways of emerging bacterial pathogens and key enzymes involved.
• Chemical and chemoenzymatic synthesis of structurally defined bacterial polysaccharides as vaccine candidates.
• Bioengineering systems to produce glycan conjugate vaccines.
• Novel adjuvants that improve polysaccharide and glycan-based vaccines
• Efforts to generate broad-spectrum glycan-based vaccines.
Keywords: Bacterial polysaccharide, Vaccine, Structure, Synthesis, glycan, Biosynthesis
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