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Genetics and Biosynthesis of Lipopolysaccharide O-Antigens
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Wendy J. Keenleyside, Chris Whitfield
These O-PS modifications are not confined to O-PSs synthesized by Wzy-dependent pathways. A number of Klebsiella O serotypes express galactose-containing OPSs synthesized by an ABC transporter-dependent pathway. These share a common d-galactan I backbone but differ in modifications to this structure (Table 1). The O-PS biosynthesis clusters of serotypes O1 and O8 have been cloned and sequenced and shown to direct synthesis of d-galactan I only (91,147); the locus responsible for the d-galactan II modification is undetermined. The O antigen of serotype O8 differs from O1 in the presence of O-acety1 groups on the d-galactan I backbone. Characterization of the O8 d-galactan I biosynthesis cluster indicates that the O-acetyl transferase is not encoded by the biosynthesis cluster (91). It is conceivable that prophages are also responsible for the serotype-specific modifications of d-galactan I.
Molecular Aspects of Anti-Polysaccharide Antibody Responses
Published in Maurizio Zanetti, J. Donald Capra, The Antibodies, 2002
Kurt Brorson, Pablo Garcia-Ojeda, Kathryn E. Stein
Galactans are polymers of galactose isolated from a variety of natural sources such as plant tissues and exudates [64, 65], microbial sources [66] and animal mucosal tissues [67]. Plant galactans, sometimes referred to as arabinogalactans, are complexes consisting of an a(1: 3) or a(1: 6) linked galactan core and branch structures containing other sugars such as glucuronic acid, arabinose and rhamnose. Core linkage structures vary, depending on the natural source. For example, the galactan core of gum Ghatti (an exudate gum from Anogeissus latifolia) is mostly a(1: 6) linked while the galactan core of gum Arabic (an exudate gum from acacia trees) is mostly a(1: 3) linked [65, 68]. Synthetic polygalactans are available to determine antibody fine specificities in a manner more precise than possible with natural galactans [69, 70].
Phenotypic whole-cell screening identifies a protective carbohydrate epitope on Klebsiella pneumoniae
Published in mAbs, 2022
Sophia K. Berry, Steven Rust, Carolina Caceres, Lorraine Irving, Josefin Bartholdson Scott, David E. Tabor, Gordon Dougan, Graham Christie, Paul Warrener, Ralph Minter, Andrew J. Grant
The in vivo activity of B39 against K. pneumoniae 961842, an O2+ strain, conflicts with the in vitro binding data, which could suggest that conversion of D-galactan-I → D-galactan-III may depend on environmental factors that differ between in vivo and in vitro conditions. Nonetheless, the high prevalence of the gmlABC locus in ST258 clones suggests the expression of D-galactan-III is important in a nosocomial setting. This work highlights the need for a wider phenotypical analysis of the O-antigens from a large collection of K. pneumoniae O1 and O2 strains. Moreover, given the discrepancies we observed here between in vitro binding data and in vivo mAb activity, future work should aim to explore the expression of D-galactan-I and D-galactan-III in vivo in different tissues, under different in vitro conditions, and in the environment.