Extraction, separation, and partial characterization of Brucella abortus antigens

Brucella abortus isolates strain 19 (a vaccinal strain) and 458 (a virulent field isolate) were analyzed for antigenic differences. Whole cell preparations were extracted with detergents, salt solutions, and phenol-acetic acid-water (PAW). Antigens were separated by starch block electrophoresis and sucrose density gradient centrifugation, serotested, and chemically analyzed. Six distinct precipitin lines were observed for the PAW extract against hyperimmune bovine antisera. With sucrose density centrifugation or starch block electrophoresis, antigens were separated into (i) complement-fixing (CF) antigens and (ii) antigens that did not fix complement but formed precipitin bands. Reciprocal CF tests with purified CF antigen could not differentiate between the antigens from either isolate of Brucella.