Serological crossreactivity between Brucella abortus and Yersinia enterocolitica 0:9 I immunoblot analysis of the antibody response to Brucella protein antigens in bovine brucellosis.

Sera from three groups of Brucella abortus infected cattle were examined in immunoblots with the following antigens: sodium dodecyl sulfate/mercapto ethanol (SDS/ME) extracts of two rought B. abortus strains (45/20 and RB51) and rough B. ovis, smooth lipopolysaccharides (SLPS) from B. abortus strain 99 and Y. enterocolitica 0:9, and a cytoplasmic extract from smooth B. abortus strain 19-S. The sera groups were: (1) 26 sera from animals, experimentally infected with B. abortus strain 544, which were all positive in the conventional brucellosis serological tests; (2) 152 sera from naturally infected cattle herds with varying titres in the conventional brucellosis tests, and (3) 30 sera from naturally infected cattle with varying titres in the conventional brucellosis tests and from which B. abortus was cultured. B. abortus strain 99 and Y. enterocolitica serotype 0:9 SLPS staining showed up frequently in all sera groups and correlated well with the strength in the conventional brucellosis tests, confirming the immunodominance of SLPS in B. abortus infections. Another immunodominant component of 50-80 kDa was found in the rough B. abortus 45/20 antigen preparation but not in the B. abortus RB51 and in the B. ovis cell extracts. This component was also recognised by sera from Y. enterocolitica 0:9 infected cattle and is probably a protein-lipopolysaccharide complex. Although many of the sera from B. abortus infected cattle with high titres in the conventional brucellosis tests showed complex protein staining patterns in blots, no protein bands other than the 50-80 kDa bands were found to be immunodominant.