Discovery of Bordetella oligosaccharide - extracellular glycan common to genus Bordetella. Structure, immunogenicity and possible implications for host-pathogen interactions
Pertussis pathogenesis is the result of multiple virulence factors. In addition to the secretory proteins of Bordetella pertussis, surface molecules such as adhesins and endotoxin play a role in the pathogenesis of this disease. There are conflicting reports on the existence and nature of the Bordetella capsular polysaccharides or exoglycans. The data concerning the glycome of Bordetellae is incomplete. This conclusion is primarily derived from genomic data, with only limited indications regarding the actual structures. In this study, we present novel data on the exoglycan produced by all strains and species of the investigated bacteria from the genus Bordetella, including Bordetella pertussis, Bordetella parapertussis, Bordetella bronchiseptica, and Bordetella holmesii. This is the first time this type of data has been provided. The exoglycan was consistently recovered from the chemically defined culture media of various Bordetellae species and strains. The compound was identified by nuclear magnetic resonance (NMR) as a free hexasaccharide released into the medium and thus received its name, Bordetella oligosaccharide (BOS). The biosynthetic origin of the BOS was confirmed by NMR combined with metabolic labeling in culture, using 13C,15N-L-glutamate as a primary carbon source. The identification of BOS has the potential to enhance our comprehension of the complete array of virulence factors contributing to the pathogenesis of Bordetella pertussis, particularly in regard to their relations with other Bordetella species. In the field of vaccine design, glycan structures are typically of utmost importance; however, they were hardly ever considered in the case of pertussis.