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Chlamydial lipopolysaccharide
1Universität für Bodenkultur Wien, Institute of Chemistry, Vienna, Austria. pkosma@edv2.boku.ac.at
Abstract:
Chlamydiae are obligatory intracellular parasites which are responsible for various acute and chronic diseases in animals and humans. The outer membrane of the chlamydial cell wall contains a truncated lipopolysaccharide (LPS) antigen, which harbors a group-specific epitope being composed of a trisaccharide of 3-deoxy-D-manno-oct-2-ulosonic (Kdo) residues of the sequence alpha-Kdo-(2-->8)-alpha-Kdo-(2-->4)-alpha-Kdo. The chemical structure was established using LPS of recombinant Escherichia coli and Salmonella enterica strains after transformation with a plasmid carrying the gene encoding the multifunctional chlamydial Kdo transferase. Oligosaccharides containing the Kdo region attached to the glucosamine backbone of the lipid A domain have been isolated or prepared by chemical synthesis, converted into neoglycoproteins and their antigenic properties with respect to the definition of cross-reactive and chlamydia-specific epitopes have been determined. The low endotoxic activity of chlamydial LPS is related to the unique structural features of the lipid A, which is highly hydrophobic due to the presence of unusual, long-chain fatty acids.
Insights
Chlamydia
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Chlamydiae are intracellular parasites causing human and animal diseases.
- Their outer membrane contains a unique lipopolysaccharide (LPS) antigen.
Purpose of the Study:
- To elucidate the chemical structure of the chlamydial LPS.
- To determine the antigenic properties of the Kdo epitope.
Main Methods:
- Recombinant E. coli and S. enterica strains expressing chlamydial Kdo transferase.
- Chemical synthesis and isolation of Kdo-containing oligosaccharides.
- Neoglycoprotein conversion and antigenic analysis.
Main Results:
- The structure of the chlamydial Kdo epitope was established.
- Antigenic properties of Kdo oligosaccharides were determined.
- Chlamydial LPS exhibits low endotoxic activity due to unique lipid A.
Conclusions:
- The Kdo epitope is a key antigenic determinant in Chlamydia.
- Structural analysis provides insights into chlamydial pathogenesis and potential vaccine targets.