ANTIGENIC CHARACTERIZATION AND ANALYSIS OF THE HUMAN IMMUNE-RESPONSE TO OUTER-MEMBRANE PROTEIN-E OF BRANHAMELLA-CATARRHALIS

Outer membrane protein E (OMP E) is a 50-kDa major OMP of Branhamella catarrhalis. Polyclonal antisera and four monoclonal antibodies (MAbs) to OMP E were generated to study its antigenic structure. All antibod ies recognized epitopes in all 19 B. catarrhalis strains tested by imm unoblot assays. By flow cytometry, it was determined that MAbs 1B3 and 9G10d recognized epitopes which are expressed on the surface of the i ntact bacterium, while MAbs 1C11 and 7C10 recognized epitopes which we re buried within I-he outer membrane. A competitive enzyme-limited imm unosorbent assay showed that MAbs 1B3 and 9G10d recognize the same or closely related epitopes. Proteinase K treatment of whole bacterial ce lls revealed that MAbs 1B3 and 9G10d recognize a surface exposed epito pe located in the 17-kDa region towards the amino terminus of OMP E. T he human serum sad mucosal antibody responses to OMP E in adults with chronic bronchitis were studied. A majority or these patients had immu noglobulin A to OMP E in sputum supernatants. None of ten adults who e xperienced lower respiratory tract infections due to B. catarrhalis de monstrated a clear-cut rise in antibody titer to OMP E in serum or spu tum supernatant. This study has demonstrated that OMP E has at least o ne surface exposed epitope which is highly conserved among strains of B. catarrhalis and which is located in the amino-terminal 184 amino ac ids of the molecule.