Classification ofPseudomonas syringaewith Monoclonal Antibodies Against the Core and O-side Chains of the Lipopolysaccharide

Abstract

Six murine hybridomas producing monoclonal antibodies (MAbs) toward Pseudomonas syringae lipopolysaccharide (LPS) were established. Two of these, Ps-core-1 (IgG2a) and Ps-core-2 (IgG3), were found to be specific against an outer-core oligosaccharide epitope, and demonstrated reactivity only in immunoenzymatic assays. Core-specific antibodies recognized unsubstituted LPS bound to nitrocellulose paper, implying that the core-specific epitope is altered or masked by the attachment of the O-chain. The Ps-O:2-1, Ps-O:2-2, Ps-O:2-3 (all IgM), and Ps-O:3-1 (IgG3) MAbs were found to be reactive with O:2 and O:3 polysaccharides of LPS with known chemical structures. O-antigen-specific MAbs were positive for agglutination and precipitation reactions, enzyme-linked immunosorbent assay (ELISA), and immunoblotting analysis. The expression of MAb-specific epitopes by 223 strains belonging to 19 pathovars of P. syringae, 16 strains of 8 other pseudomonad spp. as well as 5 strains of Agrobacterium and Xanthomonas were studied in ELISA. Both core-specific MAbs recognized 99% of the strains from 17 pathovars of P. syringae. However, they did not react with any strains from P. s. coriandricola and P. s. lachrymans or strains of other species of bacteria. Bacteria exhibiting the O:2 phenotype of LPS were detected only within P. s. atrofaciens (28 strains), P. s. glycinea, (5 strains) and P. s. syringae (12 strains). The O:2 phenotype of LPS was detected among strains from P. s. morsprunorum (1 strain) and P. s. syringae (4 strains). The chemical bases of the O:2 and O:3 serogroup specificity were deduced and a new serological classification scheme for P. syringae proposed