title: Peroxidase-mediated toxicity to schistosomula of Schistosoma mansoni.
abstract: Guinea pig eosinophil peroxidase (EPO) was capable of killing schistosomula of Schistosoma mansoni in vitro when combined with hydrogen peroxide and a halide. Killing was measured by 51Cr release, by microscopic evaluation of viability, and by reinfection experiments in mice. Parasite killing was dependent on each component of the EPO-H2O2-halide system, was completely inhibited by catalase and azide, and was partially inhibited by cyanide. The EPO-mediated system required 10(-4) M H2O2 and 10(-4) M iodide at pH 7.0, and the schistosomula were killed with exposure to this system of less than 30 min at 37 degrees C. At pH 6.0, the EPO-mediated system showed significant cidal activity with 10(-6) M iodide. Canine neutrophil peroxidase (myeloperoxidase [MPO]) was also able to kill schistosomula in vitro in the presence of 10(-4) M H2O2 and 10(-4) iodide at pH 7.0 and pH 6.0. Physiologic concentrations of chloride (0.1 M) could substitute for iodide at pH 7.0 and pH 6.0 as the halide cofactor; however, at pH 7.0, a higher concentration of enzyme was required. These findings with isolated enzyme systems are compatible with a role for peroxidase in the host defense against schistosomula.
mesh_terms: D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D051379:Mice; D009195:Peroxidase / Q000494:pharmacology*; D010544:Peroxidases / Q000494:pharmacology*; D012550:Schistosoma mansoni / Q000276:immunology; D012552:Schistosomiasis / Q000276:immunology*
chemical_list: D002712:Chlorides; D006861:Hydrogen Peroxide; D010544:Peroxidases; D009195:Peroxidase