Branhamella catarrhalis: antigenic determinants and the development of the IgG subclass response in childhood.

A recently developed whole cell ELISA was used to investigate the development of IgG subclass antibodies to Branhamella catarrhalis in childhood. In addition, SDS-PAGE and immunoblotting were used to study the interaction between the outer membrane proteins (OMPs) of B. catarrhalis and IgG subclass antibodies. Specific IgG3 antibodies were undetectable or present only in low amounts in children less than 4 years old but were an important constituent of the response of older children. OMPs prepared from different isolates had similar molecular masses and bound IgG with identical immunoblotting patterns. Binding appeared subclass-specific, with IgG3 binding to the broadest range of OMPs. These findings should provide a better understanding of the pathogenic role of this organism and suggest possible strategies for the development of a vaccine.