Extracellular antigens of Moraxella bovis

The extracellular antigens of 2 isolates of Moraxella bovis were isolated by ammonium sulfate precipitation of cell-free culture filtrate, purified by filtration and differentiated by immunodiffusion and immunoelectrophoretic techniques. The extracellular filtrate from rough types had 2 specific extracellular antigens in addition to those in the culture filtrate of smooth-type cells of the same isolate. The extracellular antigens produced by smooth-type cells were identical in all isolates of Moraxella bovis. The serotype-specific extracellular antigens of 2 isolates were serologically identical but were different from those of a 3rd isolate. The possibility of serotyping M bovis isolates, on the basis of their extracellular rough-type antigens, was suggested. Although both serotype-specific antigens were destroyed by trypsin treatment, 1 antigen was also heat-labile and partially destroyed by formalin treatment.