Serum antibody response to outer membrane proteins of Moraxella (Branhamella) catarrhalis in patients with bronchopulmonary infection

A Western blot (immunoblot) method for detecting antibodies against outer membrane protein (OMP) epitopes of Moraxella (Branhamella) catarrhalis was evaluated. Paired serum samples from patients suspected of M. catarrhalis (n = 38) and non-M. catarrhalis (n = 25) bronchopulmonary infection were examined for the presence of antibodies of the immunoglobulin M (IgM), IgG, and IgA classes to OMPs from M. catarrhalis by a gel electrophoresis-immunoperoxidase technique (Western blotting); sera from 40 healthy adult blood donors were also included. A significantly (P = 0.004) more frequent occurrence of IgM-class antibodies and/or an increase in the number of IgG-class antibodies against different M. catarrhalis OMPs from acute- to convalescent-phase serum samples was found for patients with M. catarrhalis (79%) than for patients without M. catarrhalis (40%). IgM-class antibodies against OMPs of M. catarrhalis were found in acute- and/or convalescent-phase serum samples form 58% of patients with M. catarrhalis and 32% of patients without M. catarrhalis. Fifty percent of patients with M. catarrhalis and 16% of patients without M. catarrhalis had, from acute- to convalescent-phase serum samples, an increased number of IgG-class antibodies directed against different OMPs. A total of 34% of patients with M. catarrhalis and 4% of patients without M. catarrhalis had, from acute- to convalescent-phase serum samples, an increased number of IgA-class antibodies directed against different OMPs. The present study indicates that M. catarrhalis is one of the bacteria involved in acute exacerbations of chronic bronchitis.