DMB labelling for detection and analysis of capsular polysaccharides

Summary

A collaboration I contributed to while at ETH. Bacterial capsules are major virulence factors and vaccine antigens, but routine methods to detect and analyze them had largely disappeared. This study reports a biochemical method that releases ABC transporter-dependent (group 2 and 3) capsular polysaccharides by mild acid hydrolysis of their Kdo linkages and tags them fluorescently with DMB (1,2-diamino-4,5-methylenedioxybenzene); anion-exchange chromatography of the labelled material then reveals the presence, relative abundance, and length distribution of these antigens in extraintestinal pathogenic Escherichia coli (ExPEC). My contribution was insight into the DMB labelling chemistry.

Abstract

Bacterial capsules are major virulence factors enabling systemic infection by undermining innate and adaptive immunity. Capsular polysaccharides are also the antigen in some of the most successful antibacterial vaccines, including the pneumococcal, neisserial and Hib conjugate vaccines. However, it remains exceptionally challenging to study capsules, primarily due to their high chemical diversity and the limited methods available for their detection and analysis. We describe a robust biochemical method for detection and analysis of ABC transporter-dependent capsular polysaccharides, a major class of capsules that are associated with extraintestinal pathogenic Escherichia coli (ExPEC). The method involves release and fluorescent tagging of polysaccharides from the cell surface. Anion exchange chromatography of labelled samples reveals the presence, relative abundance, and length-distribution of these diverse polysaccharide antigens. The method provides a modern approach to detecting the capsule phenotype, bridging a critical gap left by the decline of serotyping assays. It will enhance our understanding of fundamental capsule biology and advance the development of capsule-targeting vaccines.

Read the paper

• Publisher version (doi:10.1101/2025.01.29.635457)

How to cite

Rutschmann, C.; Vershynina, K.; Mathew, C.; Piëch, L.; Sulewska, M.; Schilling, P. E.; Wenner, N.; Larsson, L.; Bertola, A.; Barazzone, E. C.; Domocos, I.; Mores, C. R.; Ndem-Galbert, J. R.; Turgay, Y.; Schumann, R.; de Viragh, S.; Lavender, H.; Tang, C.; Diard, M.; Sunagawa, S.; Wetter, M.; Fiebig, T.; Slack, E.; Keys, T. G. DMB labelling for detection and analysis of capsular polysaccharides. bioRxiv 2025. https://doi.org/10.1101/2025.01.29.635457

@misc{Rutschmann2025DMB,
  author = {Rutschmann, Christoph and Vershynina, Kateryna and Mathew, Corina and Piëch, Lucas and Sulewska, Małgorzata and Schilling, Philipp E. and Wenner, Nicolas and Larsson, Louise and Bertola, Anouk and Barazzone, Elisa Cappio and Domocos, Ioana and Mores, Carine Roese and Ndem-Galbert, Jackie Raisse and Turgay, Yagmur and Schumann, Raffael and de Viragh, Shirin and Lavender, Hayley and Tang, Chris and Diard, Médéric and Sunagawa, Shinichi and Wetter, Michael and Fiebig, Timm and Slack, Emma and Keys, Timothy G.},
  title = {{DMB labelling for detection and analysis of capsular polysaccharides}},
  howpublished = {bioRxiv},
  year = {2025},
  doi = {10.1101/2025.01.29.635457},
  url = {https://doi.org/10.1101/2025.01.29.635457}
}