Glycan and protein analysis of glycoengineered bacterial E. coli vaccines by MALDI-in-source decay FT-ICR mass spectrometry

Nicolardi, S.; Danuser, R.; Dotz, V.; Dominguez Vega, E.; Kaabi, A. al; Beurret, M.; Anish, C.; Wuhrer, M.

doi:doi:10.1021/acs.analchem.1c04690

Bacterial glycoconjugate vaccines have a major role in preventing microbial infections. Immunogenic bacterial glycans, suchas O-antigen polysaccharides, can be recombinantly expressed and combined with specific carrier proteins to produce effective vaccines. O-Antigen polysaccharides are typically polydisperse, and carrier proteins can have multiple glycosylation sites. Consequently, recombinant glycoconjugate vaccines have a high structural heterogeneity, making their characterization challenging. Sincedevelopment and quality control processes rely on such character-ization, novel strategies are needed for faster and informative analysis.Here, we present a novel approach employing minimal samplepreparation and ultrahigh-resolution mass spectrometry analysis forprotein terminal sequencing and characterization of the oligosaccharide repeat units of bacterial glycoconjugate vaccines. Threeglycoconjugate vaccine candidates, obtained from the bioconjugation of the O-antigen...Show moreBacterial glycoconjugate vaccines have a major role in preventing microbial infections. Immunogenic bacterial glycans, suchas O-antigen polysaccharides, can be recombinantly expressed and combined with specific carrier proteins to produce effective vaccines. O-Antigen polysaccharides are typically polydisperse, and carrier proteins can have multiple glycosylation sites. Consequently, recombinant glycoconjugate vaccines have a high structural heterogeneity, making their characterization challenging. Sincedevelopment and quality control processes rely on such character-ization, novel strategies are needed for faster and informative analysis.Here, we present a novel approach employing minimal samplepreparation and ultrahigh-resolution mass spectrometry analysis forprotein terminal sequencing and characterization of the oligosaccharide repeat units of bacterial glycoconjugate vaccines. Threeglycoconjugate vaccine candidates, obtained from the bioconjugation of the O-antigen polysaccharides fromE. coliserotypes O2,O6A, and O25B with the genetically detoxified exotoxin A fromPseudomonas aeruginosa, were analyzed by MALDI-in-source decay(ISD) FT-ICR MS. Protein and glycan ISD fragment ions were selectively detected using 1,5-diaminonaphtalene and a 2,5-dihydroxybenzoic acid/2-hydroxy-5-methoxybenzoic acid mixture (super-DHB) as a MALDI matrix, respectively. The analysis of protein fragments required the absence of salts in the samples, while the presence of salt was key for the detection of sodiated glycanfragments. MS/MS analysis of O-antigen ISD fragments allowed for the detection of specific repeat unit signatures. The developed strategy requires minute sample amounts, avoids the use of chemical derivatizations, and comes with minimal hands-on time allowing for fast corroboration of key structural features of bacterial glycoconjugate vaccines during early- and late-stage developmentShow less

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Glycan and protein analysis of glycoengineered bacterial E. coli vaccines by MALDI-in-source decay FT-ICR mass spectrometry