Immune response to Moraxella catarrhalis in children with otitis media: opsonophagocytosis with antigen-coated latex beads.

Opsonic antibody activity against Moraxella catarrhalis was determined in sera from children with otitis media. The antibody was determined with a new assay utilizing outer membrane antigen-coated latex beads. Antigen-coated beads opsonized in heat-inactivated pooled human serum phagocytosed 47.5 +/- 36.1 beads per 100 neutrophils compared to 15.6 +/- 10.2 beads per 100 neutrophils opsonized in hypogammaglobulinemic serum (p < .025). Antigen-coated beads opsonized in homologous sera from 11 children with M. catarrhalis otitis media demonstrated increased opsonic activity in convalescent sera (34.6 +/- 27.1) compared to acute sera (15.5 +/- 6.7; p < .05). These data suggest that infection with M catarrhalis is associated with the development of opsonic antibody.