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A monoclonal antibody against a carbohydrate epitope in lipopolysaccharide differentiates Chlamydophila psittaci from Chlamydophila pecorum, Chlamydophila pneumoniae, and Chlamydia trachomatis

Můller-Loennies, Sven, Gronow, Sabine, Brade, Lore, MacKenzie, Roger, Kosma, Paul, Brade, Helmut
Glycobiology 2006 v.16 no.3 pp. 184-196
Chlamydia trachomatis, Chlamydophila pecorum, Chlamydophila pneumoniae, Chlamydophila psittaci, bacteria, biosynthesis, carbohydrate binding, cross reaction, crystal structure, diagnostic techniques, disaccharides, enzyme-linked immunosorbent assay, epitopes, immunization, ligands, lipopolysaccharides, mice, monoclonal antibodies, surface plasmon resonance, thin layer chromatography, transferases, veterinarians
Lipopolysaccharide (LPS) of Chlamydophila psittaci but not of Chlamydophila pneumoniae or Chlamydia trachomatis contains a tetrasaccharide of 3-deoxy-[alpha]-D-manno-oct-2-ulopyranosonic acid (Kdo) of the sequence Kdo(2[rightwards arrow]8)[Kdo(2[rightwards arrow]4)] Kdo(2[rightwards arrow]4)Kdo. After immunization with the synthetic neoglycoconjugate antigen Kdo(2[rightwards arrow]8)[Kdo(2[rightwards arrow]4)]Kdo(2[rightwards arrow]4) Kdo-BSA, we obtained the mouse monoclonal antibody (mAb) S69-4 which was able to differentiate C. psittaci from Chlamydophila pecorum, C. pneumoniae, and C. trachomatis in double labeling experiments of infected cell monolayers and by enzyme-linked immunosorbent assay (ELISA). The epitope specificity of mAb S69-4 was determined by binding and inhibition assays using bacteria, LPS, and natural or synthetic Kdo oligosaccharides as free ligands or conjugated to BSA. The mAb bound preferentially Kdo(2[rightwards arrow]8)[Kdo(2[rightwards arrow]4)]Kdo(2[rightwards arrow]4)Kdo(2[rightwards arrow]4) with a K[subscript d] of 10 [micro]M, as determined by surface plasmon resonance (SPR) for the monovalent interaction using mAb or single chain Fv. Cross-reactivity was observed with Kdo(2[rightwards arrow]4)Kdo(2[rightwards arrow]4) Kdo but not with Kdo(2[rightwards arrow]8)Kdo(2[rightwards arrow]4)Kdo, Kdo disaccharides in 2[rightwards arrow]4- or 2[rightwards arrow]8-linkage, or Kdo monosaccharide. MAb S69-4 was able to detect LPS on thin-layer chromatography (TLC) plates in amounts of <10 ng by immunostaining. Due to the high sensitivity achieved in this assay, the antibody also detected in vitro products of cloned Kdo transferases of CHLAMYDIA: The antibody can therefore be used in medical and veterinarian diagnostics, general microbiology, analytical biochemistry, and studies of chlamydial LPS biosynthesis. Further contribution to the general understanding of carbohydrate-binding antibodies was obtained by a comparison of the primary structure of mAb S69-4 to that of mAb S45-18 of which the crystal structure in complex with its ligand has been elucidated recently (Nguyen et al., 2003, Nat. Struct. Biol., 10, 1019-1025).