A 200 kDa protein is associated with haemagglutinating isolates of Moraxella (Branhamella) catarrhalis

Moraxella catarrhalis adheres to human erythrocytes by means of a proteinaceous, trypsin sensitive, heat modifiable haemagglutinin. A 200 kDa protein was found to be associated with haemagglutinating isolates of M. catarrhalis. This protein was present on all haemagglutinating isolates (n = 17), but was absent on the non-haemagglutinating isolates (n = 23) examined. This protein demonstrated heat-modifiable properties in sodium dodecyl sulfate and was degraded by trypsin. Immunoblot assays with polyclonal antiserum indicated that the 200 kDa protein was associated exclusively with haemagglutinating isolates and antibodies to this protein did not recognise epitopes on non-haemagglutinating isolates. This protein, which appears to be a surface expressed protein may be a haemagglutinin of M. catarrhalis.