title: Identification of outer membrane proteins as target antigens of Pseudomonas aeruginosa Homma serotype M.
abstract: Pseudomonas aeruginosa is routinely serotyped in Japan by using the Homma scheme. The serotypes (O serotypes) are based on the chemical structure of the O-polysaccharide portion of the lipopolysaccharide (LPS). However, the nature of the Homma serotype M antigen has remained obscure because strains classified as serotype M usually have the rough phenotype. I characterized the target antigen of serotype M. The results of Western blotting (immunoblotting) showed that commercially available typing monoclonal antibody (MAb) against serotype M specifically bound to outer membrane protein (Opr) G and that typing rabbit antiserum specific for serotype M mainly contained antibodies against Oprs F and H2. These Oprs were distributed among all P. aeruginosa strains tested, including the serotype standard, serotype M and nontypeable strains, and a series of LPS-core-defective mutants derived from strain PAC1. However, the rough mutants derived from strain PAC1 agglutinated with the anti-serotype M antibodies, whereas the smooth strains did not. LPS preparations from serotype M strains possessed few or no polysaccharide chains. These strains had higher levels of binding activity with anti-serotype M MAb, as well as with anti-lipid A MAb, which specifically bound to the cell surface of the rough-natured gram-negative bacterial strains with high activity. The anti-serotype M antiserum also contained rough-LPS-specific antibodies, but the epitope was distributed among only a few strains. The results suggested that the Oprs acted as the serotype M antigen and that LPS did not. In conclusion, the rough strains agglutinated with anti-Opr antibodies and were distinguished as serotype M from the smooth strains of other serotypes, because the antibodies were accessible to the cell surface lacking O polysaccharides. I supposed that Homma serotype M is an index of the rough nature of P. aeruginosa strains rather than one of the O serotypes.
authors.affiliation: Sumitomo Pharmaceuticals Research Center, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yokota
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D015153:Blotting, Western; D008070:Lipopolysaccharides / Q000494:pharmacology; D009154:Mutation / Q000276:immunology; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000235:genetics / Q000276:immunology*; D011817:Rabbits; D012703:Serotyping
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D008070:Lipopolysaccharides