The serological response to rough and smooth brucella antigens in cattle vaccinated with Brucella abortus strain 45/20 adjuvant vaccine.

Cattle not previously exposed to Brucella abortus responded to a single dose of Br. abortus 45/20 adjuvant vaccine by producing low titres of agglutinins for rough brucella antigens and little or no agglutinins to the smooth antigens. Moderate titres of non-agglutinating antibodies reacting with both rough and smooth antigens were also produced. After a second dose of 45/20 vaccine higher titres of rough agglutinins and low titres of antibodies reacting with smooth antigens were produced. High titres of non-agglutinating antibodies reacting with both rough and smooth antigens were also produced. Animals previously exposed to smooth Br. abortus, either as strain 19 vaccine or virulent organisms, produced high titres of antibodies to smooth antigens soon after vaccination with 45/20 adjuvant vaccine. High titres of antibodies reacting with rough and smooth antigens were also produced. The evidence suggests that the Br. abortus strain 45/20 shares a surface antigenic component with smooth brucellae. The possible relationship of this to the protective antigen is discussed.