Use of Monoclonal Antibodies To Identify Phospholipase C as the Enterotoxic Factor of the Bifunctional Hemolysin-Phospholipase C Molecule of Vibrio cholerae O139

Two hybrid clones producing monoclonal antibodies (MAbs) raised against the purified enterotoxic hemolysin-phospholipase C (HlyPC) bifunctional molecule of a Vibrio cholerae O139 strain were used to study its enterotoxicity in relation to its hemolytic and enzymatic activities. Fab fragments of MAbs from ascites produced by the two hybrids neutralized the hemolytic activity of HlyPC, leaving the enzymatic activity unaffected. In ligated rabbit ileal loop and infant mouse intestine, the Fab fragments of the MAbs were not able to neutralize the enterotoxicity of HlyPC, suggesting that PC rather than Hly is the enterotoxic moiety of the molecule. The enterotoxicity of the purified PC molecule isolated from an Hly⁻ spontaneous mutant of the HlyPC-producing parent strain further confirms this contention. The Hly molecule isolated from a PC⁻ mutant was not diarrheagenic.