Antigenic analysis of Vibrio cholerate O1 by crossed immunoelectrophoresis

Antigens from Vibrio cholerae O1 were analyzed by crossed immunoelectrophoresis (CIE) using sera from immunized rabbits. Thirty different anode-migrating antigens were detected in sonicated antigen preparations of V. cholerae. These antigens were numbered in order to establish a reference precipitation pattern. Antigen no. 30 was identified as the lipopolysaccharide (LPS) antigen, because it reacted with (i) periodic acid-Schiff (PAS) reagent and (ii) the affinity-purified anti-LPS antibodies. Treatment with proteinase K demonstrated that most of the precipitation lines were due to proteins, a part of which were localised at the cell surface. The major outer membrane protein was found to be closely associated with the precipitation line due to the LPS (antigen no. 30). The antigenicity and immunogenicity of V. cholerae cells killed by different methods (merthiolate, heat, phenol, formalin) were examined. As determined by CIE, killing with merthiolate preserved most of the major components of V. cholerae. Heat, phenol and formalin altered the antigenic mosaic of V. cholerae. These results suggested that CIE can be used to analyze several aspects of V. cholerae antigens.