Differences in sensitivity of Schistosoma mansoni schistosomula, Dirofilaria immitis microfilariae, and Nematospiroides dubius third-stage larvae to damage by the polyamine oxidase-polyamine system.

The effect of the polyamine oxidase (PAO)-polyamine system on some helminths was examined in vitro. Both Schistosoma mansoni schistosomula and Dirofilaria immitis microfilariae were highly sensitive to this system, the latter more so than the former. In contrast, exsheathed third-stage larvae of Nematospiroides dubius were resistant to the effects of the PAO-polyamine system. After incubation of microfilariae with either spermine or spermidine in the presence of serum containing PAO (bovine serum or human retroplacental serum) or partially purified PAO, damage of worms occurred, compatible with our criteria for worm death. Similar results were obtained with schistosomula by using spermine. The damage seemed to be mediated by PAO products other than hydrogen peroxide because catalase did not protect either parasite. Our data demonstrate that helminths may be damaged by products of the PAO-polyamine system.