Uncovering bacterial pseudaminylation with pan-specific antibody tools
Pseudaminic acids (Pse) are a family of carbohydrates found within bacterial lipopolysaccharides, capsular polysaccharides and glycoproteins that are critical for the virulence of human pathogens. However, a dearth of effective tools for detecting and enriching Pse has restricted study to only the most abundant Pse-containing glycoconjugates. Here, we devise a synthesis of - and {beta}-O-pseudaminylated glycopeptides to generate pan-specific monoclonal antibodies (mAbs) that recognise - and {beta}-configured Pse and its C8 epimer (8ePse) presented within glycans or directly linked to polypeptide backbones. Structural characterisation reveals the molecular basis of Pse recognition across a range of diverse chemical contexts. Using these mAbs, we establish a glycoproteomic platform to provide unprecedented depth in mapping the Pse glycome of Helicobacter pylori, Campylobacter jejuni, and Acinetobacter baumannii strains. Finally, we demonstrate that the mAbs recognise diverse capsule types in multidrug-resistant Acinetobacter baumannii and enhance phagocytosis to eliminate infections in mice.