Soluble antigens of virulent and attenuated biotypes of Brucella abortus

Several methods were used to characterize three Brucella abortus biotypes (1, 5, and 7), including the attenuated vaccine strain S-19. Chemical analysis did not reveal remarkable differences among these strains, and only minor differences were noted in elution patterns of soluble extracts subjected to column chromatography. Qualitative and quantitative differences in extract components were demonstrated, however, by polyacrylamide gel isoelectric focusing. A distinctive difference was the presence of components in extracts from one or more of the virulent biotypes that were absent in similar preparations from the attenuated strain. In addition, one component common to all virulent strains was absent in strain S-19. Results of immunodiffusion experiments employing adsorbed and unadsorbed antisera also suggested that the quantity, quality, and surface distribution of various cellular antigens differed among the biotypes studied.