Somatic O antigen relationship of Brucella and Vibrio cholerae

The antigenic relationship between Brucella species and Vibrio cholerae was examined by agglutinin and agglutinin-absorption tests by using rabbit antisera. Brucella antisera agglutinated only the Inaba serotype of V. cholerae and at low titer. Inaba-reactive antibody was absorbed by either heat-stable (100 C, 2 hr) Ogawa or Inaba O antigens. Cholera antisera from rabbits immunized with either O or HO antigens of either Ogawa or Inaba serotypes contained brucella agglutinins. This activity was absorbed completely from Ogawa antisera by either Ogawa or Inaba O antigens but only partially from Inaba antisera by Ogawa O antigen. These findings support the claim of Gallut that the cross-reaction is due to heat-stable O antigens of V. cholerae rather than heat-labile flagellar antigens as described in many text books. The cross-reactive component is more dominant in the Inaba than in the Ogawa serotype of V. cholerae.