Preparation of procoligenoids from Escherichia coli heat-labile enterotoxins.

Heat-labile enterotoxins from Escherichia coli strains of porcine and human origin polymerize on heating to form high-molecular-weight aggregates, "procoligenoids," analogous to procholeragenoid derived from the cholera enterotoxin. This aggregation is accompanied by loss of biological activity (toxicity). Further heating results in the release of B-subunit oligomers, coligenoids, analogous to choleragenoid. Further studies are needed to determine whether, like procholeragenoid, the procoligenoids are superior antigens in stimulating gut immunity after parenteral administration.