Inactivation of Clostridium difficile cytotoxin by the neutrophil myeloperoxidase system

The cytotoxin of Clostridium difficile was examined for sensitivity to oxidant secretory products of neutrophils. Exposure to myeloperoxidase, H₂O₂, and a halide resulted in loss of toxin activity measured by tissue-culture cytotoxicity. The peroxide requirement was provided by reagent H₂O₂, a peroxide-generating enzyme (glucose oxidase), or a peroxide-producing intestinal microorganism, Lactobacillus acidophilus. Human neutrophils stimulated by phorbol myristate acetate caused similar toxin inactivation. In both the cell-free and the neutrophil systems, inactivation of toxin required halides and was abrogated by azide, cyanide, or catalase. Neutrophils from patients with lack of myeloperoxidase or failure to produce H₂O₂ were impaired in toxin inactivation unless myeloperoxidase or H₂O₂, respectively, was added. The reducing agent 2-mercaptoethanol enhanced toxin activity. These data suggest a similarity between C difficile cytotoxin and the classic thiol-activated cytolysins. Moreover, they raise the possibility that neutrophils are involved in oxidative detoxification of microbial products.