Demonstration of shared and unique immunological determinants in enterotoxins from Vibrio cholerae and Escherichia coli.

Immunodiffusion and biological neutralization studies demonstrated that the heat-labile enterotoxin (LT) from Escherichia coli has antigenic determinants in common with each of the isolated subunits (A and B) of the enterotoxin (choleragen) from Vibrio cholerae. Each of the enterotoxins also possesses unique antigenic specificities. Monospecific antiserum to LT was prepared by immunization with antigens derived by immune precipitation of E. coli cell-free supernatant with isolated specific anticholeragenoid antibodies. This antiserum neutralized the biological acitivity of both LT and cholera enterotoxin and recognized antigens of both in immunodiffusion. This antiserum was adsorbed with choleragenoid to remove antibodies directed against the shared "B" immunological determinants. The neutralizing effect of the antiserum on cholera toxin was completely removed, but the neutralizing activity against the E. coli preparations was retained, although somewhat reduced. Antisera to the isolated subunits (A and B) of cholera enterotoxin neutralized the biological activity of cholera enterotoxin and LT. These antisera also recognized the homologous and heterologous antigens in immunodiffusion. Multiple forms or conformations of LT and its components may explain the diversity of the properties which have been reported for it.